biology first year complete 14 chapters

BIOLOGY NOTES FOR CLASS FIRST YEAR

Composer: Seetal Daas

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First Year Biology Notes 1

Composed by: Seetal Daas

CHAPTER 1

INTRODUCTION TO BIOLOGY

Definition of Biology:

Biology is the study of living organisms. It is derived from Greek words.

Classification of Living Organism

According to the modern classification given by R.H.Whittaker in 1969, living

organisms are divided into five major kingdoms, which are:

Kingdom Monera

It includes all prokaryotes, unicellular organisms. For example, Bacteria and

Cyan bacteria.

Kingdom Protoctista(Protista)

It includes unicellular Eukaryotic organisms, which are in between plants and

animals. e.g. Chlamydomonas, Euglena, Paramecium etc.

1. Kingdom Fungi:

It includes non-chlorophyllus multi-cellular, thallophytic organisms having cell

wall. For example, all types of fungi, unicellular to multi-cellular like

Mushrooms and Yeast etc.

2. Kingdom Plantae:

It includes all chlorophyllus multi-cellular Eukaryotic living organisms having

cellulose cell wall. For example, apple, red wood etc.

3. Kingdom Animalia:

It includes all Eukaryotic multi-cellular, non-chlorophyllus organisms having no

cell wall. For example, Hydra, Earthworm, Human Beings etc.

Eukaryotic Organisms

Those organisms, which have true membranous structure in their cells, like

mitochondria, golgi bodies, endoplasmic reticulum. e.g. All plants, Higher

animals.



Prokaryotes

Those living organisms, which do not have true membranous structure in their

cells. e.g. Bacteria, Blue green algae.

Phyletic Lineage

All living organisms of today belong to a common ancestor and each species of

organism arranged no ancestor to descendent order with rest of the group

evolved from one that immediately preceded.

Branches of Biology

1. Molecular Biology:

It is a recent branch of biological science that deals with the structure and

function of the molecules that form structure of cell and organelles that take part

in the biological processes of a living organism (Nucleic acid – Protein

molecule)

2. Micro Biology:

It deals with the study of micro-organisms (viruses, bacteria, protozoan etc)

3. Environmental Biology:

It deals with the study of environment and its effect on organisms.

4. Marine Biology:

It deals with the study of organisms inhabiting the sea an ocean, and the

physical and chemical characteristics of their environment.

5. Fresh Water Biology:

It deals with the life dwelling in fresh waters, physical and chemical

characteristics of fresh water bodies affecting it.

6. Parasitology:

It deals with the study of parasitic organisms, their life cycles, mode of

transmission and interaction with their hosts.

7. Human Biology:

The branch of biology deals with all biological aspects of man regarding

evolution, anatomy physiology, health, inheritance etc.



8. Social Biology:

Social biology is concerned with the social interactions with in a population of a

given species, especially in human beings focuses on such issue as whether

certain behavior is inherited or culturally induced.

9. Biotechnology:

This is a very recent branch introduce in biological sciences. It deals with the

use of data and techniques of engineering and technology for the study and

solution of problems concerning living organisms particularly the human

beings.

Biological Method

In order to solve the biological problems (any animal or plant disease or

environmental hazard), following steps are necessary.

1. Hypothesis:

An educated guess or fact regarding the biological problem.

Inductive Reasoning

Isolated facts to reach a general idea that explain the biological problem.

Deductive Reasoning

Accurate experimentation, true conclusions or results regarding the biological

problems.

2. Observation/Experiments:

The given hypothesis is checked with the help of observation and experiments

and then on the basis of it a theory or rule is established.

3. Theory:

If observations and experiments come true then hypothesis is taken true,

otherwise it is rejected. Only on the basis of true hypothesis a theory is

established.

4. Law/Principle:

When theory is proved to be true under all tested circumstances then it is

accepted as a law.



Malaria

• Malaria means disease cause by bad air.

• Actual Causative agent is plasmodium (Vector Female, Anopheles

Mosquito)

• Leveran first discover plasmodium in human R.B.C.

• Ronald Ross discovered plasmodium in the stomach of female Anopheles

Mosquito.

• Grassi discover the complete life cycle of Plasmodium in human being and

mosquito.

Antibiotics:

Substances or chemicals, which are required in small quantity to inhibit the

growth of Microorganisms. The first antibiotic was penicillin discovered by

Fleming. Other examples are: Erythocin, Rythocin, Gentamycin, Ampicillin etc.

Chemotherapy:

Treatment with drug or chemical.

Radiotherapy:

Treatment with radiations, like α, β, γ or X-rays.

Hydroponics:

It is the science of terrestrial plants growing in aerated solutions (add CO2

under pressure, in any liquid also known as aerated water). This technique is

also known as soil less or water culture.

Advantages

1. Control weeds and soil disease problems.

2. Area required for cultivation is minimum.

3. Can be applied on any part of the world.

4. Main purpose is to fulfill the food requirements of rapidly increasing world

population.

Cloning:



Production of duplicate copies of genetic material, cells or entire multicellular

living organisms, occurring naturally in plants or animals. Duplicate copies are

known as clones.

Natural Cloning

• Identical twin, triplet in humans.

• Asexual reproduction in plants and animal.

• Regeneration and wound healing.

• Growth of tumor cells or cancers.

Artificial Cloning

• Cloning of human cells such as liver cells, skin cells, blood cells are quite

helpful to develop human organs in laboratories.

• There are also enormous advantages of cloning in the field of medicine and

agriculture. Examples are vegetative reproduction of fruits and nuts by

grafting.

• Artificial cloning is also used for treating disease, production of medically

significant substances such as Insulin, growth hormones, interferon and anti-

thrombin etc.

Level of Biological Organization

Life is built on chemical foundation and the life of all living organisms emerges

on the level of cell. The foundation of cell is based on elements. Atoms of

different elements unite to form molecules. Living organism usually form

extremely large and complex molecules by living matter which is present in their

bodies. The molecules of living organisms are mostly composed of carbon and

provide building blocks of living matter. Mostly living matter of an organism is

composed of organic molecules along with inorganic compounds (minerals) are

also associated for e.g. Human blood. Simple organic molecules present in living

organisms are sugar, glycerol and fatty acids, amino acids, purine and

pyramidines. Similar types of cells form-tissues, similar tissues form organs,

different organs coordinating with each other form system and different systems

combine to form a living organism.

Cell → Tissues → organs → System → An Individual

Biological organization can be divided into the following levels:



Sub-Atomic Particles:

“Particles that make up an atom are called sub-atomic particles”.

For e.g. electron, proton and Neutron.

Atom:

“The smallest particle of an element that retains the property of that element”.

For example: Hydrogen, carbon and oxygen etc.

Molecule:

“The combination of similar and different atoms is called molecules”.

For example Hydrogen and oxygen combines to form water molecules.

Organelle:

“A structure with in a cell that performs a specific function”.

For example: Mitochondria, chloroplast etc.

Cell:

“The smallest structural and functional unit of life”.

For example: A nerve cell

Tissue:

“A group of similar cells that performs a specific function”.

For example: Nervous tissue.

Organ:

“A structure with in an organism usually compose of several tissue types that

forms a functional unit”.

For example: The brain

Organ System:

“Two or more organs working together in the execution of a specific bodily

function”.

For example: The nervous system.

Multicellular Organism:

“An individual living thing composed of many cells are called Multicellular

organisms”.

For example: Pronghom antelope.



Specie:

“A group of very similar inter breeding organisms constitutes a species”.

For example Herd of pronghom antelope.

Population:

“Members of same species inhabiting the same area are considered as

population”.

For example: Herd of pronghom antelope.

Community:

“Population of several species living and interacting in the same area form a

community”.

For example: Snake, antelope and hawk.

Eco-System:

“A community with its environment including land, water and atmosphere,

constitute an eco-system”.

Biosphere:

“The part of earth inhibited by living organisms, both living and non-living

components.”



CHAPTER 2

BIOLOGICAL MOLECULES

Biochemistry: Biochemistry is a branch of biology, which deals with the study of chemical

components and chemical processes in living organisms.

Water (H2O):

Main Characteristics of Water • Chemically it is “Dihydrogen oxide”

• It is the most abundant component in living cell.

• Its amount varies approximately from 70 to 90% and life activities occur in

the cell due to the presence of water.

• It is a polar molecule, means that it has a very slightly negative end (the

oxygen atom) and a very slightly positive end (the hydrogen atom).

• Due to its polarity, H2O molecules form hydrogen bonds.

Important Biological Properties of Water

(1) Best Solvent • Water is an excellent solvent for polar substances, when ionic substances

dissolved in water, dissociate into positive and negative ions.

• Non-ionic substances, having charged groups in their molecules, are

dispersed in water.

• Because of solvent property of water, almost all reactions in cells occur in

aqueous media.

(2) High Heat Capacity • Water has great ability of absorbing heat due to its high specific heat

capacity.

• The specific heat capacity of water is the number of calories required to raise

the temperature of 1g water through 1ºC.

• The thermal stability plays an important role in water based protoplasm of

individual’s metabolic activities.

(3) High Heat of Vaporization • Liquid water requires higher amount of heat energy to change into vapours

due to hydrogen bonding which holds the water molecules together.

• It provides cooling effect to plants when water is transpired, or to animals

when water is respired.

(4) Act as Amphoteric Molecule • Water molecule acts both as acid and a base. As acid, it gives up electron to

form H+ ion, while as a base, it gains electron to form OH ions.



• H2O ↔ H+ + OH-

• It acts as buffer and prevents changes in the pH of living body.

(5) Protection

• Water is an effective lubricant that provides protection against damage resulting

from friction.

• It also forms a fluid cushion around organs that helps to protect them from

trauma.

(6) As Reagent /Turgidity

• Water acts as a reagent in many processes such as photosynthesis and

hydrolysis reactions.

• It also provides turgidity to the cells.

Organic Compounds: Those compounds containing carbon (other than carbonates) are called organic

compounds. E.g: carbohydrates, Proteins, Lipids and Nucleic acid.

Inorganic Compounds: Those compounds, which are without carbon, are called inorganic compounds.

E.g: water, carbon dioxide, acids, bases and salts.

Macromolecules:

Huge and highly organized molecules which form the structure and carry out

the activities of cells are called “Macromolecules” Macromolecules can be

divided into four major groups.

• Proteins

• Carbohydrates

• Lipids

• Nucleic acids.

Monomers: Macromolecules are composed of large number of low molecular weight

building blocks or subunits called “Monomers” E.g: Amino-acids (Protein).

Condensation: The process by which two monomers are joined is called “Condensation”.

In this process two monomers join together when a hydroxyl(OH) group is

removed from one monomer and a hydrogen (-H) is removed from other

monomer.

This type of condensation is called “Dehydration Synthesis” because water is

removed (dehydration) and a bond is made (synthesis).



Hydrolysis: A process during which polymers are broken down into their subunits

(monomers) by the addition of H2O called “Hydrolysis “. It is just reverse of the

condensation.

Functional Groups: These are particular group of atoms that behave as a unit and give organic

molecules their physical, chemical properties and solubility in aqueous solution.

E.g

• Methyl group (CH3-)

• Hydroxyl or Alcohol group (OH-)

• Carboxylic acid or Organic-acid group (COOH-)

• Amino or Amine group (NH2-)

• Carbonyl group (CO=)

• Sulfhydryl group (SH-)

Proteins: These are the complex organic compounds having C, H,O and N as elements

but sometimes they contain P and S also. Due the presence of N they are called

“Nitrogenous Compounds” Proteins constitute more than 50% of dry weight of

cell. They are present in all types of cells and in all parts of the cell.

Chemical Composition of Proteins Proteins are polymers of amino-acids and number of amino-acids varies from a

few to 3000 or even more in different proteins.

These amino-acids are linked together by specialized bond or linkage called

“peptide linkage”

Each protein has a unique sequence of amino-acids that gives the unique

properties to molecules.

Amino Acid It is the basic structural unit of proteins and all amino-acids have an “Amino

group (NH2-) and a “Carboxyl group (COOH-)” attached to the same carbon

atom, also known as “Alpha carbon”. The have the general formula as:

1. A hydrogen atom.

2. An amino (NH2) group.

3. A carboxyl group (COOH)

4. “Something else” this is the “R” group.

R

?

H2N ? C ? COOH



(Amino group) ? (Carboxylic group)

H

“R” may be a “H” as in glycine, or CH3 as in alanine, or any other group. So,

amino acids mainly differ in the R-group.

Polypeptides: Amino Acids are linked together to from polypeptides of proteins. The amino

group of one amino acids may react with the carboxyl group of another

releasing a molecule of water. E.g: Glycine and analine may combine to form a

dipeptiede

Peptide Linkage/ Bond: The linkage between the hydroxyle group of carboxyl group of one amino-acid

and the hydrogen of amino-group of another amino-acid release H2O and C-N

link to form a bond called “Peptide bond”.

Types of Proteins on the Basis of Structure

There are four basic structural levels of proteins.

(A) Primary Structure: • A polypeptide chain having a linear sequence of amino-acids.

• Disulphide (S-S) bond is other important characteristic of the primary protein.

E.g: Insulin Polypeptide chain.

B) Secondary Structure: • In this type polypeptide chain of amino-acids become spirally coiled.

• This coiling results in the formation of a rigid and tubular structure called

“Helix”

C) Tertiary Structure: • Polypeptide chain bends and folds upon itself forming a globular shape.

• It is maintained by three types of bonds. Namely ionic, hydrogen and

disulfide (S-S).

(D) Quaternary Structure: • This type is usually present in highly complex proteins in which polypeptide

tertiary chains are aggregated and held together by hydrophobic interactions,

hydrogen and ionic bonds.

E.g: Haemoglobin molecule.



Functions of Protein • They Build many Structures of the cell E.G: Plasma Membrane.

• All enzymes are proteins and in this way, they control the whole metabolism

of the cell.

• Skin, nails, hair, feather, horn etc. contain portion called keratin.

• Casein is the milk portion and ovalbumin is the egg white protein.

• Collagen present in bones, cartilage, etc. is the most abundant protein in

higher vertebrates.

• Protein acts as antibodies, antigens and fibrin etc.

Carbohydrates: It is a group of organic compounds having carbon, oxygen and hydrogen, in

which hydrogen and oxygen are mostly found in the same ratio as in water i.e.

2:1 and thus called “Hydrated carbons” They are found about 1% by weight and

generally called Sugars or saccharides” due to their sweet taste except

polysaccharides.

Classification of Carbohydrates The carbohydrates can be classified into following groups on the basis of

number of monomers.

1. Monosaccharide

2. Oligosaccharides

3. Polysaccharides.

(1) Monosaccharides: • These are called “Simple Sugars”, because they cannot be hydrolysed further

into simple sugars.

• Their general formula is “Cn H2n On

• They are white crystalline solids with sweet taste and soluble in water.

• They are present in various fruits and vegetables.

E.g: Glucose, Galactose, Fructose and Ribose etc. Monosaccharide can be sub-

classified according to umber of carbon atom present in each molecule. They

may be triose, (Glycerose), tetrose (erythrose), pentose, (ribose), hexone

(glucose) or heptose (Glucoheptose) having 3,4,5 ,6 and 7 carbon atoms

respectively.

(2) Oligosaccharides: • These carbohydrates yield 2 to 10 monosaccharides molecules on hydrolysis

• Disaccharides are the most common and abundant carbohydrates of

oligosaccharides.

• These sugars are comparatively less sweet in taste, and less soluble in water.

E.g: Maltose, Sucrose and lactose etc.



(3) Polysaccharides: • These are the most complex and most abundant carbohydrates in nature.

• They are of high molecular weight carbohydrate which on hydrolysis yield

mainly monosaccarides or products related to monosaccharide.

• These sugars are formed by the condensation of hundreds of thousands of

monosaccharide units.

• They are tasteless and only sparingly soluble in H2O.

E.g: Strach, cellulose Glycogen, Dextrin Agar, pectin and Chitin etc.

Functions of Carbohydrates

• Carbohydrates are the potential source of energy.

• They act as storage food molecules and also work as an excellent building,

protective and supporting structure.

• They also form complex conjugated molecules.

• They are needed to synthesize lubricants and are also needed to prepare the

nectar in some flowers.

Lipids: These are naturally occurring compounds, which are insoluble in water but

soluble in organic solvents. They contain carbon, hydrogen and oxygen like

carbohydrates rate but in much lesser ratio of oxygen than carbohydrates. These

biomolecules are widely distributed among plants and animals.

Classification of Lipids Following are the important groups of lipids.

1. Acylglycerol (fats and oil)

2. Waxes

3. Phospholipids.

4. Terpenoids.

(1) Acylglycerol (Fats and Oil) • These are found in animals and plants, provide energy for different metabolic

activates and are very rich in chemical energy.

• They are composed of glycerol and fatty acids. The most widely spread

acylglycerol is triacyl glycerol, also called triglycerides or natural lipids.

There are two types of acylgycerol

(A) Saturated Acylglycerol • They contain no double bond.

• They melt at higher temperature than unsatured acylglycerols.

• Lipids containing saturated acylgycerol are solid and known as Saturated

lipids.

E.g: Butter and Animal fat. etc.



(B) Unsaturated Acylglycerol • They contain unsaturated fatty acids i.e they contain one or more than one

double bond between carbon atom(C=C-).

• They are liquid at ordinary temperature.

• They are found in plant also called “Oil”

E.g: linolin found in cotton seeds etc.

(2) Waxes • Chemically waxes are mixtures of long chain alkanes and alcohols. Ketones

and esters of long chain fathy acids

• Waxes are widespread as protective coatings of fruits and leaves some insects

also secrete wax.

• Waxes protect plants form water loss and abrasive damage.

• They also provide water barrier for insects, birds and animals etc.

(3) Phospholipids • It is most important class of lipids from biological point of view and is

similar to riacylglycerol or an oil except that one fatty acid is replaced by

phosphate group.

• The molecule of phospholipids consists of two ends, which are called

hydrophilic (water loving end (head) and hydrophobic (water fearing) end

(Tail).

• These are frequently associated with membranes and are related to vital

functions such as regulation of cell permeability and transport process.

(4) Terpenoids • It is large and important class of lipids containing “Isoprenoid” unit (C5H8).

• They help in oxidation reduction process, act as components of essential oils

of plants and also found in cell membranes as “cholesterol

Sub-Classes of Lipids 1. Terpenes

2. Steroids.

3. Carotenoids.

(1) Terpenes

• This group based only on “Isoprenoid” unit and they are usually volatile in

nature produce special fragrance.

• Derivatives of this group are found in vitamin A and are also important

constituents of chlorophyll and cholesterol biosynthesis.

• They are utilized in synthesis of “Rubber” and “Latex”, and some of these are

used in perfumes.



(2) Steroids • This group of Terpenoids contains 17 carbon atoms ring called “steroid

nucleus”.

(3) Carotenoids • They consist of fatty acid like carbon chain and usually found in plants, for

example carotene, xanthophylls etc.

Nucleic Acids: Nucleic Acids Were First Isolated In 1870 By an Austrian Physician Fridrich

Micscher from the nuclei of pus cells. These bio molecules are acidic in nature

and present in the nucleus.

Types of Nucleic Acids Nucleic acids are of two types.

1. Deoxyribonucleic acid or DNA

2. Ribonucleic acid or RNA

Chemical Nature of Nucleic Acid: Nucleic acids are complex substances. They are polymers of units called

nucleotides. DNA is made up of deoxyribonucleotides, while RNA is composed

of ribo nucleotides.

Structure of Nucleotide Each nucleotide is made of three subunits

a) 5-carbon monosaccharide (a pentose sugar)

b) Nitrogen containing base.

c) Phosphoric acid.

(A) Pentose Sugar Pentose sugar in RNA is ribose, while in DNA it is deoxyribose.

(B) Nitrogenous Base Nitrogenous bases are of two types

(I) Pyrimidines (Single Ringed): These are cytosine (abbreviated as C),

thymine (abbreviated as T), and uracil (abbreviated as U).

(II) Purines (Double Ringed): These are adenine (abbreviated as A) and

guanine (abbreviated as G).

C) Phosphoric Acid

Phosphoric acid (H3PO4) has the ability to develop ester linkage with OH

group of pentose sugar.



Formation of Nucleotide: Formation of nucleotide takes place in two steps. First the nitrogenous base

combines with pentose sugar at its first carbon to form a “Nucleoside”. In

second step the phosphoric acid combines with the 5th carbon of pentose sugar

to form a “Nucleotide”.

(A) Mononucleotides • They exist singly in the cell or as a part of other molecules.

• These are not the part of DNA or RNA and some of these have extra

phosphate groups e.g ATP.

(B) Dinculeotides • These nucleotides are covalently bounded together and usually act as co-

enzymes

E.g NAD (Nicotinamide dinucleotide).

(C) Polynucleotides

• Nucleotides are found in the nucleic acid as “Polynucleotide” and they have a

variety of role in living organisms.

• They usually perform the function of transmitters of genetic information.

Conjugated Molecules • Two different molecules, belonging to different categories, usually combine

together to form “Conjugated molecules”.

• These conjugated molecules are not only of structural, but also are of

functional significance.

• They play an important role in regulation of gene expression.

(A) Glycoprotein and Glycolipids

Carbohydrates may combine with proteins to form glycoprotein or with lipids to

form glycolipid.

Functions

a) Most of cellular secretions are glycoprotein’s in nature.

b) Both glycoproteins and glycolipids are integral structural components of

plasma membranes.

(B) Lipoproteins Combination of lipids and proteins form lipoproteins.

Function They are basic structural framework of all types of membranes in the cells.



(C) Nucleoproteins Nucleic acids have special affinity for basic proteins. they are combined

together to form nucleoproteins.

Functions

The nucleoproteins (Histone) are present in chromosomes.

Things to be Remember • Proteins-Berzelius and G.J murlder.

• Lipids-Bloor in 1943.

• DNA –Hereditary material.

• RNA- carrier of genetic information.

• rRNA – (Ribosomal RNA)- Double stranded.

• Transcription- Formation of mRNA.

• Translation –Formation of Proteins by ribosmes.

Diffusion:

The movement of ions or molecules from the region of higher concentration to

the region of lower concentration is known as diffusion.

Examples 1. If a bottle of perfume is opened in a corner of a room, it can be smelt in the

entire room.

2. Leakage of gas pipes can be smelt from a farther point.

3. If we drop a KMNO4 crystal in clean water, then after sometime the

crystals will dissolve and color of water changes from colorless to purple.

Factors on which rate of Diffusion Depends

1-Size

Small molecules move faster than larger ones.

2-Temperature

Rate of diffusion will be high at high temperatures.

3-Concentration Gradient

Greater the difference in concentration and shorter the distance between two

regions, greater will be the rate of diffusion.

Facilitated Diffusion: Diffusion of the substances across the cell membrane through the specific

carrier proteins is known as facilitated diffusion. These membrane transport



proteins are channel proteins, receptors, cell pumps or carriers, made up of

usually proteins and don’t require energy for transport.

Passive Transport:

Movement of substances in and out of the cell, caused by simple kinetic motion

of molecules, doesn’t require energy of ATP is known as passive transport, e.g.

Simple diffusion and facilitated diffusion.

Osmosis: The movement of water molecules from the region of higher concentration to the

region of lower concentration through a semi-permeable membrane, is known as

osmosis.

Types of Osmosis

A- Endosmosis The movement of water molecules into the cell, when it is placed in hypotonic

solution is called as Endosmosis.

B- Exomosis The movement of water molecules out of the cell when the cell is placed in a

hypertonic solution.

Active Transport: The movement of ions or molecules across the cell membrane against the

concentration gradient i.e. from lower concentration to higher concentration with

the help of specific transport proteins in the cell membrane, at the expense of

cell’s metabolic energy – ATP is called active transport.

Examples

1. Sodium-Potassium pump in nerve cells which pump Na+ out of the nerve

cell, and K+ into the cell against the concentration gradient.

2. Cells lining the intestine can transport glucose actively from a lower

concentration in the intestinal contents to higher concentration in blood.

3. In plants phloem loading is an ex. Of active transport.

Imbibitions: Adsorption of water and swelling up of hydrophilic (water loving) substances is

known as imbibitions.



Hydrophilic Substances: Those which have great affinity for water are hydrophilic e.g. starch, gum,

protoplasm, cellulose, proteins, e.g. seeds swell up when placed in water.

• Wrapping up of wooden framework during rainy seasons.

• Dead plant cells are hydrophilic colloids.

• The chemical potential of water is a quantitative expression of the free energy

associated with the water.

• UNIT: Joules/mole

• This term has been replaced by water potential

Water Potential (Psi): It is the difference between the fee energy of water molecules in pure water and

energy of water in any other system, or solution. Water potential is a relative

quantity, depends upon gravity and pressure.

Q = Q* + f (concentration) + f (pressure) + f (gravity)

Β* is standard water potential or pure water potential of valve O Mpa.

Unit: Megapascal’s – Mpa

(1 Mpa = 9.87 atmospheres)

Uses

The direction of water flow across cell membrane can be determined. It is a

measure of water status of the plant.

Osmotic Pressure: The pressure exerted upon a solution to keep it in equilibrium with pure water

when the two are separated by a semi permeable membrane is known as Osmotic

pressure. It prevents the process of osmosis.

Osmotic Potential The tendency of a soln to diffuse into another, when two solutions of different

concentrations are separated by a differentially permeable membrane.

• It is represented by βs for pure water βs = 0

• The βs decrenses as the osmotic concentration increases.

• Osmotic concentration is the number of osmotic-ally active particle per unit

volume.

• Osmotic potential has been replaced by solute potential.

• The concentration of solute particles in a solution is known as solute potential

βs. It value is always negative.



Pressure Potential Βp: When a cell is placed in pure water or in aqueous solution with higher water

potential than the cell sap water follows into the vacuole by endosmosis thru cell

membrane and tonoplast. Due to this inflow of water, the tension developed by

the cell wall causes an internal hydrostatic pressure to develop, which is called as

pressure potential.

Β = βs + βp or Qp = Q – Qs

In turgid cells βp is equal and opposite to βs

Turgid Cell:

When the cell is fully stretched with maximum pressure potential, the water

cannot flow into it. This condition is called turgidity and the cell is turgid.

Plasmolysis: If a cell is placed in a hypertonic solution, which has more negative solute and

water potentials then water will come out of the cell, by exosmosis and

protoplasm starts separating from cell wall leaving a gap between cell wall and

cell membrane. This withdrawal of protoplasm from cell wall is known as

plasmolysis.

The point where protoplasm just starts separating from cell wall is known as

“Incipient plasmolysis” when it is completely separated, full plasmolysis occurs.

In plasmolysis cell βp = 0 therefore βw = βs

Deplasmolysis: When a cell is placed is a hypotonic solution or pure water, there will be an inflow

of water by endosmosis. Protoplasm starts expanding and presses cell wall due to

which pressure potential develops and water potential becomes less negative.

This swelling of cell is known as deplasmolysis.

Water and Minerals Uptake by Roots 1. Absorption of water and mineral salts takes place through root system.

2. Roots are provided with enormous number of tiny root hairs.

3. These root hairs are more in number in tap root system.

4. Roots hairs are out growths of epidermal cells.

5. Roots hairs increase the surface area for absorption.

6. Most of the absorption takes place at root tips.

7. From hairs and epidermal cells water flows thru cortex, endodermis,

pericycle and them enters xylem.

There are 3 pathways for water to enter xylem.



A- Cellular Pathway In this route water flows through cell to cell. Water enters the root hairs or

epidermal cells down a concentration gradient: it flows through cell wall and cell

membrane and enters the adjacent cell from where water may again flow towards

the deeper cells by osmosis.

B- Symplast Pathway Cytoplasm of the cortical cells are interconnected by small pores in the cell wall

known as plasmodesmata.

These pores provide another way of transporting water and solutes across the

plasma membrane at root hairs.

C- Apoplast Pathway The cell walls of cortical and epidermal cells are hydrophilic and form a

continuous matrix. Soil solution flows freely through these hydrophilic walls. The

movement of soil soln. through extra cellular pathway provided by continuous

matrix of cell walls is known as “Apoplast pathway”.

Simplast and apoplast usually both occur concurrently.

Endodermis forms a waxy barrier against the flow of water and salts known as

“casparion strip”. So, water cannot enter endodermis via apoplast pathway.

Symplast is the only way to cross the barrier. Endodermal cells actively transport

salts to pericycle resulting in high osmotic potential which causes inflow of water

by osmosis salts. Form pericycle water flows in to xylem via both symplast and

apoplast pathways.

Transpiration: The loss of water in the form of vapours from aerial parts of the plant is called

transpiration.

Types of Transpiration Following are the three types of transpiration.

A- Stomatal Transpiration It is a type of transpiration in which the water vapours escape through the

stomata. 90% of the total transpiration occurs thru this method. In isobilateral

leaves the stomata are present in both upper and lower epidermis e.g. lily and

maize leaves. In dorsiventral leaves, the stomata are only confined to lower

epidermis e.g. Brassica and sunflower.

B- Cuticular Transpiration The loss of water in the form of vapours through the cuticle of leaves is called

Cuticular Transpiration. About 5-7% of total transpiration takes place thru this



route cuticle is a waxy layer which covers the leaves and this is not completely

impermeable to water.

C- Lenticular Transpiration

It is the loss of water vapours through lenticles present in the stems of dicot

plants. Lecticles are aerating pores present in the bark formed as a result of

secondary growth. It accounts for only 1-2% of total transpiration.

Mechanism of Stomatal Respiration

Structure of Stomata:

Stomata are microscopic pores present in the epidermis of leaves and herbaceous

stems. Number of stomata are variable in different leaves and depend upon the

availability of water and climate of the region. Each stomata, is surrounded by 2

specialized epidermal cells, as guard cells, they are bean shaped or kidney shaped

and unlike other epidermal cells, they contain chlorophyll, hence perform photo-

synthesis. The inner wall of guard cell is thick while the outer wall is thin and

elastic. This structural difference is important for opening and closing of stomata.

Stages of Transpiration There are two processes involved in stomata transpiration.

+ Evaporation In the first step, water evaporates from the wet surfaces of turgid mesophyll

cells and collected in the intercellular air spaces.

+ Diffusion In this stage water vapours diffuse out from intercellular spaces where they are

in higher concentration to the outer atmosphere where they are in lower

concentration through the stomata.

Mechanism of Opening and Closing of Stomata: The opening and closing of stomata depends upon the turgidity of guard cells,

which is due to increase or decrease in the osmotic potential of the guard cells.

When water enters the guard cells by osmosis, they swell up. Since their outer

walls are thin and elastic, they stretch and bulge out. The inner thick walls cannot

stretch and so arch in and become crescent shaped thus the gap between the two

guard cells widens, opening the stomata when the guard cell lose water, they

become flaccid and the inner wall of two guard cells meet each other, closing the

stomata.

Generally, the stomata remain open during day time and close at night. Thus, light

appears as the primary factor which control the opening and closing of stomata.



Factors Regulating Opening and Closing of Stomata There are two main factors which greatly influence the opening and closing of

stomata these are

1- Light In the presence of light, chlorophyll containing guard cells synthesize sugars

which is turn increase the osmotic potential of guard cells. This increase Qs

results in endosmosis and ultimately to turgidity. While in darkness these guard

cells consume carbohydrates (sugars) by respiration for energy production or

transported to other neighbouring cells for respiration and different purposes.

This decreases the osmotic potential of guard cells leading to flaccidity because

of exomosis of water.

2- Concentration Of K+ Ions Turgidity of guard cells of many plants is regulated by K+ ion concentration.

During daytime, guard cells actively transport K+ions into them from

neighbouring cells. Accumulation of K+ ions lower the water potential of guard

cells. This causes on inflow of water by endosmosis from epidermal cells. During

night when they lose K+ ion, water potential increases. Water flows out of the

guard cells by exosmosis causing them to become flaccid which result in closure

of pore.

Factors Affecting Transpiration:

Rate of transpiration is very important for a plant because transpiration stream is

necessary to distribute dissolved mineral salts throughout the plants. Water is

transported to photosynthesizing cells of leaves. Transpiration is also very

important as it cools the plant. This is especially important in higher temperatures.

If the rate of transpiration is very high, there would be much loss of water from

the plant. So, at high temperatures the stomata almost close and reduction in the

rate of transpiration is affected. This stops witting of the leaves and of herbaceous

stems of plants.

Following are some important factors which affect the rate of transpiration.

1. Light Light affects the transpiration in two ways:

a. Light regulates the opening and closing of stomata. During sunshine, the

stomata are open, losing water vapours thus rate of transpiration is high and

during night, the stomata are closed, so the rate of transpiration is low.

b. Greater intensity of light, increases the temperature and warms the leaf, so

leaves lose heat by evaporating water molecules to cool themselves.



2. Temperature Plants transpire more rapidly at higher temperature than at low. Rise in

temperature has two effects:

i. It increases kinetic energy of water molecules, which results in rapid

evaporation of water and decreases the rate of transpiration.

ii. High temperature reduces the humidity of surrounding air. Due to this,

evaporation from surfaces of mesophyll cells increase and hence rate of

transpiration.

3. Wind The air in motion is called wind. The area around the stomata is saturated with

water vapours due to transpiration. During high velocity wind the area around

leaves is quickly replaced by fresh drier air which increases diffusion of water

molecules from air spaces to outside atmosphere and increases the rate of

transpiration.

When air is still, the rate of diffusion of water molecules is reduced and the rate

of transpiration is also reduced.

4. Humidity When air is dry, the rate of diffusion of water molecules, from the surfaces of

mesophyll cells, air spaces and through stomata, to outside the leaf increases.

So, more water is lost, increasing the rate of transpiration. In humid air, the

diffusion of water molecules is reduced. This decreases the rate of transpiration.

5. Soil Water A plant can’t continue to transpire rapidly if its moisture loss is not made up by

absorption of fresh supplies of water from the soil. When absorption of water by

roots fails to keep up with rate of transpiration, loss of turgor occurs and wilting

of leaf takes place.

Disadvantages of Transpiration 1. Transpiration is said to be necessary evil because it is an inevitable, but

potentially harmful, consequence of the existence of wet cell surfaces from

which evaporation occurs.

2. High rate of transpiration causes water deficiency and thus the excessive

transpiration leads to wilting and death of plants.

3. There is good evidence that even mild water deficiency results in reduced

growth rate of plants.



4. Excessive transpiration effects the protein synthesis, sugar synthesis and

other metabolic activities of plants.

Advantages of Transpiration

1. Water is conducted in most parts of plants due to transpiration pull or ascent

of sap.

2. It causes absorption of water and minerals from the soil.

3. Minerals dissolved in water are conducted throughout the plant body by

transpiration stream.

4. Evaporation of water from the exposed surface of cells of leaves has cooling

effect on plant.

5. Excess water is removed.

6. Wet surface of leaves allow gaseous exchange.

Guttation: It is the loss of water in the form of droplets from the ends of large leaf-veins. It

takes place through special openings called hydathodes.

Differences Between Transpiration and Guttation

Transpiration --Water escapes in the form of wapours.

--Escape water is pure and does not contain solutes.

--It takes place through stomata, and cuticle.

--It is regulated by stomata.

--Normally takes place in light

Guttation --Water escapes as liquid.

--Escaped water contain solutes.

--It takes place through hydathodes and end of veins.

--It is not a regulated process.

--Takes place at night.

Translocation of Organic Solutes: Transport of organic products of photosynthesis, like sugars from mature leaves

to the growing and storage organs in plants is called translocation. This movement

of photo assimilates and other organic materials takes place via the phloem and

is therefore called “Phloem Translocation.”

The phloem is generally found on the outer side of xylem and constitutes the bark.

The cells of phloem that take part in phloem translocation are called sieve

elements. Phloem tissue also contains companion cells, parenchyma cells, fibers



like sclereids latex containing cells. But only sieve tube cells are directly involved

in tansport of organic solutes.

Source to Sink Movement:

The translocation of photosynthesis always takes place from source to sink

tissues, therefore, the phloem transport is also referred as “source to sink

movement.”

Source The part of plant which forms the sugars or photoynthates is known as source.

For example, Mature Leaves.

Sink Sinks are the areas of active metabolism or storage of food e.g: Roots, Tubers

developing fruits, immature leaves, growing tips of roots and shoots. Some source

and sinks are interconvertible during the process of development of plants. For

example: developing and mature leaves, developing and germinating seeds, root

of sugar beets etc.

Munch Hypothesis (Mechanism of Phloem Translocation) Phloem translocation is mainly explained by a theory called the “Pressure flow

hypothesis” proposed by Ernest munch in 1930 which explains the steps involved

in the movement of photosynthates from mesophyll chloroplasts to the sieve

elements of phloem of mature leaves.

Steps The following steps explain flow theory:

1. The glucose formed during photosynthesis in mesophyll cells, is used in

respiration or converted into non-reducing sugar i.e. sucrose.

2. the sucrose is actively transported to bundle sheath cells and then to companion

cell of the nearest smallest vein in the leaf. This is called “short distance

transport” because solutes cover only a distance of two or three cells.

3. Sucrose diffuse into sieve tube cell or sieve elements by symplast pathway or

apoplast pathway. This is called phloem loading, this raises the conc. of sugars in

sieve elements, which causes osmosis of water from nearby xylem in the leaf. It

causes an increase in the hydrostatic pressure or tugor pressure.

4. The increase hydrostatic pressure moves the sucrose and other substances in

the sieve tube cells, and moves to sinks. The photo-assimilates (sugars etc) can

be moved a long distance i.e. of several meters, therefore this is known as “Long

distance transport.”



5. In the sink tissues, present at the other end of pathway, sugars are delivered by

phloem by an active process called “Phloem Unloading.” It produces a low

osmotic pressure in sieve elements of sink, as a result of this water potential

begins to rise in the phloem and causes an exosmosis of water molecules from

the sieve tubes. This causes a decrease in turgor pressure of the sieve tubes

(phloem).

6. The presence of sieve plates in the sieve elements greatly increases the

resistance along the pathway and results in the generation and maintenance of a

substantial pressure gradient in the sieve elements between source and sink. The

sieve elements contents are physically pushed along the traslocation pathway by

bulk flow, much like water flowing through a garden house.

Significance of Translocation 1. Food can be formed or stored as in sugar beets root or stem of sugar cane.

2. Sucrose is transported to sink where it is converted to glucose and used as

energy.

3. Productivity of crop can be increased by accumulation of photo-synthates in

edible sink tissues like cereal grains, pulses, ground nuts etc.

4. Fruit is formed by this process e.g. Apples, Mango etc.

Ascent of Sap

The upward movement of water and dissolved mineral salts from the roots to

the leaves gains the downward pull of gravity is known as “Ascent of Sap.”

Path of Movement The distance traveled by water is small and easy in plans like herbs and shrubs

and longest in tall trees like Pinus, red wood, eucalyptus etc. For transport,

different tissues of xylem are used for conduction of water in different plants.

These are open ended cells called “Vessels” and porous cells called “tracheids”

(Fig. From book).

A. Vessels 1. These are thick walled tube like structures which extend through several feet

of xylem tissue.

2. They range in diameter from 20μm to 70μm.

3. Their walls are lignified and perforated by pits. At the pit, cell wall is only

made up of cellulose. Pits of adjacent cells match up with each other, so that their

cavities are interconnected.

4. Xylem vessels arise from cylindrical cells, which placed end to end. They die

at maturity forming a continuous duct, providing a channel for long-distance

transport of water.



5. Rate of flow of water is 10 times faster than tracheids.

Occurrence

VESSELS are mostly found in Angiospermic plants.

B. Tracheids 1. These are individual cells about 30μm in diameter. They are several mm long

and tapered.

2. Like vessels, they are also dead, made up of thick lignified walls.

3. Their walls are perforated by small pits, which are of two types, simple and

bordered.

4. The Tracheids are connected by pits and forming a long channel for

conduction of water.

Occurrence In Ferns and Conifers.

Mechanism of Ascent of Sap Water and dissolved mineral salts present in xylem, flow in upward direction at

the rate of 15m/hour. Xylem sap ascends because of two reasons:

1. Push from below – Root Pressure Theory

2. Pull from above – Dixon’s Theory

1. Root Pressure Theory:

According to Stephen Hales

“The force which is responsible for the upward movement of water molecules in

xylem is by the pushing effect from below (i.e. roots) and is known as “Root

Pressure.” Root Pressure is created by active secretion of sals and other solutes

from the other cells into xylem sap.

This lowers the water potential of xylem sap. Water enters by osmosis, thus

increasing the level of sap. Water also take apoplast or symplast pathway to

enter the xylem cells, this increased level causes a pressure effect in xylem and

pushes the water upwards.

Objections/Failure of Theory 1. This force is unable to push water in tall plants.

2. It is seasonal.

3. Completely absent from Cycads and Conifers, so how they transfer water.

4. When a cut shoot is placed in water, the water rises in shoots although roots

are absent.

5. It is also present in plant which do not have well developed root system.



2. Transpiration Pull (Dixon’s Theory) Or Adhesion:

Cohesion-Tension Theory Dixon and Jolly proposed this theory for ascent of sap. It provides a reasonable

explanation of flow of water and minerals from the roots to leaves of plants. It

depends on:

Adhesion

Adhesion is the sticking together of molecules of different kinds. Water

molecules adhere to the cell walls of xylem cells, so that the column of water in

xylem tissue doesn’t break. The cellulose of cell wall has great affinity for water,

which helps in the process.

Cohesion

Cohesion is the attraction among molecules of same kind, which holds water

molecules together, forming a solid chain-like column within the xylem tubes.

Extensive hydrogen bonding in water gives rise to property of cohesion. The

molecules of water in xylem tube form a continuous column.

Transpiration Pull: The loss of water from the aerial parts of the plant especially through stomata of

leaves is called transpiration. During daytime, the leaf after absorbing sunlight,

raising its temperature starts transpiration. When a leaf transpires, the water

potential of its mesophyll cells drop. This drop causes water to move by osmosis

from the xylem cells of leaf into dehydrating mesophyll cells. The water

molecules leaving the xylem are attached to other water molecules of tube by H-

bonding. Therefore, when one water molecules move up the xylem, the process

continues all the way to the root, where water is pulled from the xylem cells, i.e.

tracheids or vessels.

Due to this pulling force or transpiration pull, water in xylem is placed under

tension which is transmitted to root through vessels. Tension is due to H-bonding

and strong cohesive forces between water molecules, and is strong enough to pull

water up to 200 meters or even more.

Ascent of Sap is Solar Powered

To transport water over a long distance, plants do not use their metabolic energy

or ATPs. It is done only by forces like adhesion, cohesion, evaporation and

presence of sunlight. Thus, ascent of sap is “Solar Powered.”

Significance of Ascent of Sap • Water can be transported to the different parts of the plant.

• Transpiration is regulated.



• Food is formed in presence of water.

• Photosynthesis requires water.

• Salts and minerals are also absorbed along water by roots.

Cardiac Cycle: Sequence of events which take pace during completion of one heart beat is

called “Cardiac Cycle”

Phases (I) Diastole: It is resting period of heart chambers.

(II) Systole: During which heart’s chambers contract. In cardiac cycle, blood is

circulated in whole body.

Types of Circulation

Pulmonary Circulation In pulmonary circulation following events take place.

Rt. Atrial Systol

First the blood from whole systems of body, except lungs enter in right Atrium

through superior and Inferior vena cavae into the right atrium by atiral systole,

blood comes into right ventricle from right atrium via Tricuspid valve.

Rt. Ventricle Systole

After coming of blood into the Rt. Ventricle, it goes to the lungs via pulmonary

trunk by ventricular systole, for oxygenation of blood by passing through

pulmonary valve.

Systemic Circulation In systemic circulation, following events take place.

Left Atrial Systole

When oxygenated blood comes into left atrium, then left atrial sytole causes

blood to enter left ventricle through bicuspid valve

Left Ventricular Systole

When blood reaches here it sends into aorta through aortic valve to provide

blood to body systems.

Cardiac Output The blood volume pump per minute by left ventricle into the systemic

circulation.



Heart Beat The contraction of heart chambers is known heart beat which are regular,

rhythmic.

Ventricular systole is LUB

Ventricular diastole is DUB

Time for Heart Beat 0.8 sec is time for one heartbeat.

Conducting System of Heart

It consists of;

1.AV-Node

2.SA-Node

3.AV-Bundle

4.Purkinji Fibers.

1. SA-Node

SA Node found near upper end of superior vena cava in RT. atrium

Parts 1. Specialized cardiac Muscles.

2. Autonomic Nerve endings.

Functions It Initiates the contraction of heart chambers through impulses & also transmit

to AV node.

2. AV- Node It is found in lower end of RT. Atrium. Structurally, it is similar to SA-NODE

Function It transmit nerve impulses to ventricles for contraction rhythmically.

3. Av-Bundle

AV BUNDLE are the fibers originate from AV node. The bundle divided into

Right AV bundle, Left AV bundle

Function It transmit nerve impulses to ventricles.

4. Purkinji Fibers

AV bundles red divided into small fibers which penetrate the ventricle wall also

known as purkinji fibers / Bundle of His small thin fibers.



Leukemia:

Definition “The malignant disorder of increase number of abnormal leucocytes in blood.”

Cause The cause of leukemia is unknown.

Factors Factors associated with leukemia are

• Ionizing Radiation

• Cytotoxic drugs.

• Retroviruses.

• Genetic

Effects of Disease

• In result of leukemia, normal leucocytes count become less.

• This is progressive, and fatal condition which leads to heamorrhage or

infection

Thalassemia:

Definition “Genetically impaired globin chains formation leads to impaired or defected

formation of hemoglobin.”

Genetic Disease

Thalassemia is a genetic disorder, it may be

1. Hetrozygous /Mild thalassemia:

2. Homozygous.

Type Beta-Thalassemia: When globin chain is, impaired or defected. It is most

common one.

Alpha-Thalassemia: When α-thalassemia globin chain of (HB) hemoglobin is

defected.

Kinds of Thalassemia Thalassemia Minor: When thalassemia is of heterozygous type with mild

anemia.

Thalassemia Major: When thalassemia is of homozygous type with profound

hypochromic anemia. It is more common in children & results with enlargement

of kidney.



Remedy The only remedy is transfusion of blood at regular intervals.

CVD Cardiovascular Disease

Diseases of heart, blood vessels and blood circulation are generally term as

CVD.

Atherosclerosis The disease of arterial wall with lose of elasticity, thickness of inner wall

causing narrowing of lumen, results in impairing of blood flow.

Atheromatous Plaques The narrowing is due to formation of fatty lesions called atheromatous plaque in

inner lining of arteries.

Components of Plaque These plaques consist of;

• LDL-Low Density Lipo Proteins

• Decaying Muscles Cells

• Fibrous Tissue

• Plateletes

• Clump of Blood

Causes Smoking, Hypertension, Obesity, Diabetes (Severe), family history of arterial

disease.

Effects Atherosclerosis produces no symptoms until the damage to artery is so severe

that it restricts blood flow.

Angina Pectoris If blood flow to heart muscles is restricted causes (cell damage) necrosis called

angina pectoris. Pain in chest, arm, or jaws usually during exercise.

Thrombus Formation

The formation of blood clot with in the intact blood vessel initiated by

atheromatous plaque.

Reason for Thrombus Formation Due to formation, atheromatous plaque loss of elasticity, intact blood vessel get

destroyed, blood from vessel wall comes out & later change to blood clot and

blocks the lumen of small arteries.



Result of Thrombus Formation Initially thrombus block the lumen partially result in decrease blood flow to

organs & leading to impairment of physiology of organs. Later on, thrombus

blocks the lumen completely so due to complete loss of blood supply, cells

damage occurs.

Coronary Thrombosis

Type of thrombosis when narrowing of lumen occurs in coronary blood vessels

due to formation of clot.

Effect Occlusion of coronary artery causes myocardial infarction and heart attack.

Heamorrhage The escaping of blood from intact blood vessels.

Stroke

Most dangerous type of heamorrhage is that of brain which results in paralysis

or strokes.

Haematoma The accumalation of blood in interstitial spaces known as haematoma.

This will lead to edema.

Stroke: Definition: The damage to the part of brain caused by, restriction in blood

supply or leakage of blood outside the vessels.

Characteristics Impairment of sensation, movement & function controlled by damage part of

brain.

Causes

• Hypertension

• Atherosclerosis

Hemiplegia

Damage to any, one cerebral hemisphere can cause weakness or paralyses of

one side of body called hemiplegia.



Precautionary Measures

Blood pressure should be with in normal range through proper diet. Salt should

be used in less quantities exercise should be the regular habit. Smoking must be

avoided. Person life should be free of worries.

Blood Vessels Definition: The closed vessels or tubes through which transporting medium or

blood circulate with in body called blood vessels.

Types of Blood Vessels

1. Arteries.

2. Capillaries.

3. Veins.

Arteries Definition: Thick walled blood vessels which carry blood from heart to the

organs of body.

Layers It consists of three layers.

1. Tunica Externa/ Adventitia

2. Tunica Media

3. Tunica Intima

1-Tunica Externa

It is thin but tough layer, having abundant amount of collagen fibers. It is outer

most layer.

2-Tunica Media

The middle layer has smooth muscle fibers & elastin fibers. It is the thickest

layer.

3-Tunica Intima

It consists of squamous endothelium.

Lumen:

Thick walled vessels & having smaller lumen than that of veins except arteries

of brain & related to cranium having large lumen.

Semilunar Valves: They are not present in arteries.

Branches – Divisions

Aorta divides into large arteries, large arteries into smaller arteries, smaller

arteries into arterioles, then they give rise to capillary.



At arteriole level, small sphincters are present which are known as Pre-Capillary

Sphincter.

Sphincter:

Function

They are for regulating the diastolic pressure.

Characteristics

• Arteries are elastic so during systolic pressure, they do not rupture and dilate.

• During ceasement/ stopage of systolic pressure of heart, arteries contract &

supply even flow of blood.

• The arteries carry oxygenated blood except pulmonary arteries.

Veins Definition: The thin walled blood vessels that drain blood from body

parts/organs into heart called veins.

Layers

1. Tunica Externa: Thickest layer in veins. It contains collagen, elastin and

smooth muscles cells.

2. Tunica Media: Not thicker as that of arteries. Elastic tissues and small

smooth muscle.

3. Tunica Intima: Contains endothelial cells layer.

Lumen It has large lumen and thin wall.

Semilunar Valves

They are present in veins to prevent back flow of blood in the influence of

gravity.

Tributaries Veninules -> small veins -> large veins -> vena cava.

Blood Pressure

In veins blood pressure is low and are non-pulsatile.

Characteristics

The blood flows slowly and smoothly in veins. Veins are superficial and

collapse when empty.

Capilaries The intimate microscopic closed channels of both arterial & veinous

interconnected network is called capillaries.



Diameter Capillaries are extremely narrow in diameter of about 7-10 μ.

Layers

Capillaries are thin walled vessels & contains single layer of endothelium which

offers small resistance in transport of material across the capillary wall.

Function Through diffusion and active transport of oxygen is transported to tissues &

CO2 to capillaries. Nitrogenous waste is filtered through the capillaries into

excretory tubules.

Blue Babies (Cyanosis)

Blue baby is a layman terminology. In medical science, it is known as cyanosis.

Definition: The term cyanosis” means the blueish discolouration of the skin & mucous

membrane due to excessive cone of reduced (deoxygenated haemoglobin) in the

blood & it appears when reduced Hb conc in capillaries is more than 5 gm/dl of

blood. The reduced Hb has an intense dark blue purple colour that is transmitted

through the skin.

Most Common Cause of Cyanosis

Although there are various other causes of cyanosis but the most common cause

is Congenital Cyanotic Heart Disease.

Basic Cause of Cyanosis In congenital heart diseases, there is an abnormal connection b/w right and left

side of heart, which permits the large amount of unoxygenated venous blood to

bypass the pulmonary capillaries & dilute the oxygenated blood in systemic

arteries i.e Right to Left Shunt, which results in cyanosis.

Some Examples of Congenital Heart Diseases • Some congenital heart diseases which are responsible for the abnormal

connection between right and left sides of heart are as follows.

• Atrial Septum Defect (Asd)

• Ventricular Setpum Defect (Vsd)

• Persistant Ductus A rterosus

• In all these conditions, blood begins to flow from the aorta (left side) into

pulmonary arteries (right side) & the people do not show cyanosis until late in

life when heart fails or lungs become congested.



Tetralogy of Fallot (Right –To-Left Shunt) It is the most common cause of cyanosis or blue baby in which aorta originates

from right ventricles rather than left & receives deoxygenated blood.

Human Heart:

Introduction Heart, the most powerful organ in the circulatory system is conical, hollow &

muscular organ, situated in middle mediastinum.

Position of Heart

Heart lies in the thoracic cavity between the lungs slightly towards left, enclosed

with in ribcage with the sternum in front & vertebral column behind.

Size & Weight The heart measures about 3 ½ Inches & weighs about 300 gm in males & 250

gm in females.

Main Function of Heart Heart works continuously like a muscular pump & pumps the blood to various

parts of the body to meet their nutritive requirements.

Covering of Heart Pericardium Heart is surrounded by a double layered pericarcdium. The outer layer is called

Fibrous pericardium & inner layer is called as serous pericardium.

Pericardial Fluid Fluid is secreted in b/w the two layers of pericardium which is known as

pericardial fluid.

Function Pericardial fluid acts as LUBRICANT & reduces friction b/w heart walls &

surrounding tissues during beating of heart.

Structure of Heart Human heart consists of four chambers.

Chambers of Heart

1. Right Atrium Right Atrium is the right upper chamber of heart & acts as thin walled low

pressure pump.

Openings (Inlets) of Right Atrium



1. Superior Vena Cava

2. Anfenior Vena Cava

3. Coronary Sinus

Function It receives venous blood from the whole body & pump it to the right ventricle

through the right atrioventricular (tricuspid opening) valve.

2. Left Atrium Left atrium is upper triangular chamber which is present posteriorly. It also acts

as low pressure pump.

Openings (Inlets) Of Left Atrium

Two pairs of pulmonary veins.

Function It receives oxygenated blood from the lungs through 4 pulmonary veins and

pumps it to the left ventricle through the left atrioventricular orifice (mitral or

bicuspid).

3. Right Ventricle Right ventricle is the right lower chamber of heart, which is triangular in shape.

Openings of Right Ventricle

• Tricuspids valve

• Pulmonary Aorta through pulmonary valve.

Thickness of Wall

• The wall of right ventricle is thinner than that of left ventricle in a ratio of 1:3

Size of Cavity

Cavity of right ventricle is broader than left because of thin muscular walls, and

both of these features are due to the fact that right ventricle has to pump the

blood into lungs only against low pressure system (i.e. pulmonary circulation).

Function

Right ventricle receives deoxygenated blood from right Atrium and pumps it to

the lungs through pulmonary aorta for oxygenation.

4. Left Ventricle Left ventricle is the thickest walled chamber and forms the apex of heart.



Opening of Left Ventricle

• Bicuspid or Mitral valve

• Systemic Aorta through aortic valve.

Thickness of Wall

The walls of left ventricle are 3 times thicker than those of right ventricle. Blood

pressure is 6 times high.

Size of Cavity

The cavity of left ventricle is narrower than the right ventricle because of more

muscular walls. It is due to the fact that left ventricle has to pump the blood to the

entire body against high pressure system (Systemic Circulation).

Function It receives oxygenated blood from left atrium & pumps it into the aorta.

Internal Structure of Ventrles

Interior of ventricles show two parts;

1. Rough in flowing part

2. Smooth out flowing part

1. Rough Part Trabeculae Carneae: Inflowing part of each ventricle is rough due to presence of

muscular ridges called as Trabeculae carneae.

2. Smooth Part Out flowing part of each ventricle is smooth which gives origin to pulmonary

trunk in right ventricle & Ascending Aorta in left ventricle.

Papillary Muscles

Papillary muscles are the type of Trabeculae carneae being attached by their

bases to ventricular walls, & their apices are connected to, the cusps of valves

through chorda tendinae.

Chorda Tendinae:

These are delicate fibrous chords, which connect the papillary muscles to the

cusps of Atriovertritcular valves.

Function Chorda Tendinae don’t left the valves open back into the atria when the

ventricles contract.



Septum Of Heart

1. Interatrial Septum Internally, the right & left atria are separated by a vertical membranous septum

called as Interatrial septum.

2. Interventricular Septum The right & left verticals are also separated by a thick muscular septum called

as Interventricular septum.

3. Atrioventricular Septum Atria lie above & behind the ventricles & are separated from ventricles by

Atrioven-tricular septum.

Heart Valves: Heart possesses two types of valves, which regulate the flow of blood with in

the heart.

Types of Heart Valves 1. Atrioventricular valves -> Bicuspid, Tricuspid

2. Semilunar vlaves -> Aortic valve, Pulmonary valve

1. Atrioventricular Valves

Introduction Valves, which are present in b/w the Atria & ventricles are called

Atrioventricular valves.

Types of Atrioventricular Valves They are of three types;

1. Bicuspid or Mitral Valve

Blood flows from left Atrium to the left ventricle through left atrioventricular

on orifice, which is guarded by bicuspid or Mitral valves.

Cusps: It has tow (2) cusps so it is called as bicuspid.

2.Tricuspid Valve

Blood flows from right Atrium to the Right ventricle through right

Atrioventricular orifice, which is guarded by Tricuspid.

Cusps: It has 3 cusps so it is called as TRICUSPID.

3. Semilunar Valves This is the second category of heart valves, which guard the emergence of

pulmonary & systemic Aorta.



Types of Semilunar Valves It has Two Types:

1. Aortic Valve

This valve guards the Aortic orifice in left ventricle

Cusps: It consists of 3 Semilunar cusps.

2. Pulmonary Valve

This valve guards the pulmonary orifice in right ventricle.

Cusps: It also consists of 3 semi lunar cusps.

Functions of Valves Heart valves maintain unidirectional flow of the blood & prevents its

regurgitation in the opposite direction.

Nutrition Omnivorous, i.e. It can eat any kind of organic matter. They search their food

by antennae.

Type of Digestive System Tabular Digestive System, i.e. straight slightly coiled dig tube, open at both

ends, complete dig. system.

Organs of Digestive System + Alimentary Canal

It is divisible into 3 parts

1. Fore Gut / Stomodaeum

• Mouth

• Buccal Cavity

• Oesophagus

• Crop

• Gizzard

2. Midgut / Mesenteron / Ventriculus • Hepatic Caeca

3. Hind Gut / Proctodaeum • Ileum

• Colon

• Rectum

• Anus

+ Associated Gland • Salivary Glands



1.Fore Gut: Mouth It lies at base of pre-oval cavity which is bounded by mouth part. Labrum / Upper Lip: Appendage of 3rd head segment. Mandibles: Appendage of 4th head segment. They help in mastication Maxillae: Appendages of 5th head segment. They pick up and bring food. Labium / Lower Lip: Appendages of 6th head segment. Buccal Cavity The mouth opens into buccal cavity which is short and receives the common

duct of salivary glands. Saliva cantain ‘AMYLASE’ which act upon carbohydrates. Oesophagus Buccal cavity opens into pharynx which in turn opens into oesophagus which is

a long and thin tube lying in thorax. Crop It is a large thin walled and pear shaped structure meant for storing food. Gizzard Crop opens into thick walled, rounded gizzard with muscular chitins lining

which is internally produced six teeth for grinding and straining the food. 2. Mid-Gut: It is narrow, short and tubular portion originate from gizzard. At beginning it

receives eight hepatic caeca hanging in haemocoel (body cavity filled with

white colour blood), ending blindly but opening in gut.

Enzymes from Hepatic Caeca They are lined by glandular cells, which secrete enzymes. Enzymes from hepatic caeca and mid-gut flow back into crop where digestion

takes place. Enzymes 1. Pedtidases And Trypsin Like Enzyme -> digest proteins. 2. Amylases -> complete digestion of starches 3. Lipase -> digestion of fats. Digested food form a bolus and enclosed in a thin chitinous tube secreted by

stomodael valve of gizzard. This covering is called Peritrophic Membrane. It is permeable to enzymes and digested food. This membrane protects the



lining of mid gut from damage by hard indigestible components of food. Digested food is absorbed in mid gut. 3. Hind-Gut: It has a cuticular ectodermal lining. Ileum Short, narrow and muscular ileum. The beginning of ileum is marked by 60-70

fine and long, greenish yellow Malphigian Tubules. (excretory in function). Colon Colon is long, wider and coiled portion of hind gut. Rectum Rectum is broad last part of hind gut. It absorbs H2O and conserves the much-

needed H2O from undigested food before expelling out the faeces. Anus Anus is the last opening of digestive system by which hind gut opens to outside. Salivary Glands Salivary glands are 2 in number. each present on the sides of oesophagus. Saliva

contain amylase for digestion of carbohydrates.



CHAPTER-3

ENZYMES

Enzymes(Bio-Catalysts): Enzymes are bio-catalyst which speed up the chemical reactions by lowering

“Energy of activation”.

Energy of Activation

Amount of energy which is required to start a chemical reaction. OR Energy

required to break a (particular covalent) bond present in reactant.

Nomenclature of Enzymes Enzyme is a Greek word means-En(in) and Zyme(yeast).

Discovery of Enzyme Term “Enzyme” was coined by F.W Kuhne in 1978.

Nature of Enzyme Almost all enzymes are protein in nature except few which are nitrogenous

acids like RNA-DNA(Ribozymes). Ribozymes catalyze reactions in genetic

information.

Characteristics of Enzymes • Protein in nature and are formed by living cells.

• May be intracellular or extra cellular.

• Remains unchanged during and after the reaction.

• Speed up the rate of reaction by decreasing energy of action.

• Specific in their nature.

• Heat sensitive and act on particular (optimum) temp.

• Each has specific substrate pH for its activity.

• Action can be altered by activators and inhibitors.

Classification of Enzyme (On the Basis of Structure) Pure or Simple Enzyme consist of only protein (e.g.Amylase and Pepsin)

Conjugated or Holoenzymes: May contain a non-protein part “Prosthetic group”

as well (e.g. Phosphatase and Peptidase)

Holoenzyme = Apoenzyme + Prosthetic group

…………….(Protein part)….(Non-protein part



Classification of Enzyme (On the Basis of Functions)

(1) Oxidoreductase

Catalyze reactions in which one substrate is oxidized while other is reduced.

Sub classes are:

• Dehydrogenases (convert single bond to double bond)

• Oxidases (use oxygen as oxidant)

• Peroxidases (use H202 as oxidant)

• Hydroxylases (introduce hydroxyl group)

• Oxygenases (introduce mol. Oxygen in place of double bond).

(2) Transferases

Transfer one carbon group (e.g. methyl) from one substrate to another substrate.

(3) Hydrolases

Catalyze hydrolytic cleavage of C-O, C-N, C-C and P-O bonds and other single

bonds (e.g. Peptidases, Esterases, Glycosidases and Phosphatidases).

(4) Lyases

Catalyze Elimination reactions to form double bond and reversible reaction by

adding groups across double bond (e.g. Decarboxlases, Aldolases and

Dehydratases).

(5) Isomerases

They alter the structure but not the atomic composition by moving a group from

one position to another in one molecule (e.g. Epimerases, Mutases).

(6) Ligases

Catalyze reaction in which two molecules are joined. They are also known as

synthtases.

Role of Enzyme The enzyme reacts with (energy rich or energy poor) molecules and forms an

intermediate complex that breaks into,

(a) Product

(b) Enzyme

(i) Substrate + Enzyme = Complex

(ii) Complex = Product + Enzyme

The equilibrium is achieved if the ratio of conc of reactants (substrate) and

product remains same.

Rate of reaction 1/µ Energy of activation.



Mode of Action of Enzymes 1- The action of enzyme depends on its chemical structure. A typical enzyme

molecule, has “3D” structure.

2- Has depression or pit for substrate (to fit in) known as “Active site”.

3- Any other site other than active site is called “Allosteric site”

There are two theories in respect of enzyme action, which are as follows.

Lock and Key Model Proposed by Fischer (1898) and modified by Paul Filder and D.D Woods

according to this model,

• The active site of enzyme has distinct shape.

• It allows few substrates to fit in (like a particular lock allows particular key to

fit in)

• Enzyme breaks substrate to product

FIGURE from Text Book 3.3 page #46 (The cycle of Enzyme – substrate

Interaction)

Induce Fit Model

Proposed by koshland (1959), it states that

• Enzyme binds with a substrate

• This binding induces changes in enzyme structure

• Due to this change enzyme acts and forms product

Factors Affecting Enzyme Activity The activity of enzymes depends on following factors,

1. Substrate Concentration • Increases with increase in substrate concentration (up to a limit)

• At very high concentration, activity again decreases due to saturation of

enzyme with substrate and saturation of product i.e. higher concentration of

product.

2. Temperature • Increases with in temperature (up to limits)

• Maximum activity at optimum temperature.

• Highly active at 37? C and destroyed at 100? C

• At 0? C minimum activity.

3. pH (p=potential, H=Hydrogen)

Enzymes are pH specific i.e. work in specific pH(because of protein can act

both in acidic and basic medium.



4. Water

Enzyme activity is usually maximum (up to limits) but decrease after limits

(dilution of enzyme)

5. Radiations

Enzymes become inactive due to radiations (including Alpha, Beta, Gamma

rays).

6. Co-Enzyme and Activators

Induce the enzyme activity.

Things to Be Remember

Inhibitors

Substances which decreases the activity of enzymes.

Competitive Inhibitors

Inhibitor molecules which resemble the normal substrate molecule and compete

for admission into the active site. They block the substrate from entering active

site.

Non-Competitive Inhibitors

Inhibitors bind to a part of the enzymes away from the active site (Allosteric

site). This binding cause change in the enzyme molecule shape and decrease in

enzyme activity.

Feed Back Inhibition

Common biological control mechanism of brain in order to regulate enzyme

activity.

Prosthetic Group

Non-protein part of enzyme (Co-enzyme or Co-factor)

Co-Enzyme

When prosthetic group consist of organic molecules (like FAD/NAD)

Co-Factors/Activators

When prosthetic group consist of inorganic molecules (like Ca++, Na+ etc).

Apoenzyme

Protein part of enzyme.



CHAPTER 4

THE CELL

Cell:

It is the basic structural and functional unit of life, which is able to carry out all

the life processes.

Cell Theory

The cell theory was collectively proposed by “Schleiden(1838), Schawnn(1839)

and Virchow (1858).

Important Postulates

The fundamental points of the cell theory are:

(a) The cell is the structural and functional unit of all living organism.

(b) All organisms are composed of one or more cells.

(c) New cells can arise only by division of pre-existing cells.

Thus, cell theory established the concept that the function of an organism is the

result of activities and interaction of the cell units.

Microscope

Definition:

An instrument with the help of which we see small, tiny and minute objects

which can’t be observe by naked human eye.

Types of Microscope

There are three main types of microscope.

1. Light Micro Scope

In this microscope, visible light is used as source of illumination.

2. X-Ray Microscope

X-Rays are used as source of illumination.

3. Electron Microscope

Electron beam is used as source of illumination.

There are further two sub-types of electron microscope which are:

(A)Transmission Electron Microscope

In this type, resultant image is obtained on a fluorescent screen or photographic

film.

(B)Scanning Electron Microscope

In this type, resultant image is obtained on a television screen.



Magnification of Microscope

Ability of microscope to increase the shape and size of the objects image. It can

be calculated by multiplying the power of its eye pieces with its magnifying

power of its objective.

Resolution of Microscope

The capacity of microscope to separate adjacent forms or object. Also, known

as “Minimum Resolved Distance”.

Contrast

It is important to distinguishing one part of cell from another.

* (Difference between light and electron microscope – From Text page #57)

* Prokaryotes and eukaryotes – From Text page #58)

Cell Membrane

Each cell is covered by an asymmetrical, porous, thin, semi permeable sheet

called cell membrane or plasmalemma.

Characteristics of Cell Membrane

Living part of the cell, consist of lipid + protein.

• 1.5 micron in thickness.

• Consist of two layers of lipid.

• Lipid of plasma membrane are,

1. Phospho-lipids

2. Glycolipids

3. Sterol

4. Cholesterol.

Structure of Cell Membrane

Cell membrane made up of phospho-lipids bilayer and each layer consists of,

1. Head (hydrophilic end)

2. Tail (hydrophobic end)



Head (Hydrophilic/Polar End)

Present towards the surface and formed of phosphates.

Tail (Hydrophobic/Non-Polar End)

Present towards the center and formed of fatty acids.

The non-polar ends of phospho lipids face each other, whereas their polar ends

are in association with protein or carbohydrates between every two phospo

lipids molecule lies a molecule of “Cholesterol”.

Fluid Mosaic Model

Introduction

The fluid mosaic, bilayer model was proposed by “Singer and Nicolson (1972).

Postulates of Fluid Mosaic Model

Important postulates of this model are,

(a) The cell membrane consists of lipid bilayer, in which a variety of proteins

are present.

(b) These proteins float in the fluid matrix of lipid (as ice bergs in the sea)

Arrangement of Proteins

According to the fluid mosaic model proteins are:

1. Intrinsic/Integral Proteins

These proteins penetrate the membrane surface and enter the lipid layers

(partially or wholly)

2. Extrinsic/Peripheral Proteins

These are located adjacent to outer and inner surface of membrane and float like

ice-berg in the sea.

Arrangement of Lipids

The non-polar end face each other while their polar ends are towards the

surface.

Significance of Model

• Cell membrane is flexible.

• Can change shape (because the protein and lipid of the membrane can

move).

Function of Membrane Protein

• Certain proteins themselves act as enzymes.



• Some protein act as carrier for active transport.

• Provide elasticity to membrane.

• Pores are lined by the proteins.

Function of Lipids Present in Membrane

• The lipids give rigidity to cell membrane.

• They lower the surface tension.

Functions of Cell Membrane

• It performs the two-main function.

• Protection of Protoplasm.

• Regulation of material (In and Out of cell) through its permeability.

Permeability of Membrane

The permeability of membrane is regulated by two processes.

(1) Passive Transport (Osmosis and Diffusion)

(2) Active Transport (Endocytosis, Exocytosis)

1. Passive Transport

Such type of molecules transport which does not require energy. It is further

divided into,

Diffusion

Spreading and free movement of molecules (or ions) from the region of higher

concentration to the region of lower concentration (till equilibrium state)

Significance

• Movement of oxygen and digested food (glucose, amino acids, fatty acids)

into the cell.

• Movement of excretory waste out of cell.

Osmosis

Diffusion of water by semipermeable membrane or the movement of solvent

molecules from higher to lower concentration across semi permeable

membrane.

Significance

• Liquids, primarily water molecules enter and leave the cell by Osmosis.



• It helps to maintain a balance (osmotic pressure) in and out of cell.

2. Active Transport

Such type of molecule transport which require energy. Or Movement of

molecules against the concentration by the expenditure of energy through a

carrier (i.e. movement of molecules from the region of lower concentration to

higher concentration by protein using ATP as energy.

Significance

Absorption of excess food (glucose), ions (K+ and Na+) takes place by Active

transport.

Conditions

• It is unidirectional.

• ATP provides energy.

• Protein act as carrier.

Active transport is further subdivided into,

(1) Phagocytosis and Pinocytosis (Endocytosis).

(2) Exocytosis.

Phagocytosis

Process of picking and ingestion of large solid particle by plasma membrane

(which cannot enter by diffusion, osmosis or active transport).

Significance

• Ingestion of solid food particles.

• WBCs pick foreign particles (certain bacteria)

Pinocytosis

Process of fluid intake, for absorbing fluid by forming pinocytic vesicle (the

fluid which cannot be absorbed by osmosis, enters through it)

Significance

Helps in absorption of hormones, lipids etc.

Cell Wall

The cell wall is the outer most covering of a plant cell. It is composed of

cellulose (a carbohydrate) and some other chemical substances.

This hard covering gives form, firmness and strength to the plant cell.



In a young cell, it is thin and delicate but in a mature cell it becomes thick due

to the deposition of various chemical substances on its inner surface.

There are three layer of cell wall.

1. Middle (Lamella)

• First formed cell plate.

• Cementing layer between two daughter cells.

• Composed of Ca++ and Mg++ pectate.

• Cells are separated when this layer is dissolved.

2. Primary Wall

• First product of cell synthesized by protoplast.

• In young cells, it is thin and elastic while it becomes thick and rigid on

maturity.

• Made up of Hemicellulose (50%), cellulose (25%) and pectate substances.

3. Secondary Wall

• Composed of cellulose.

• Present inside the primary wall.

• Can be modified through the deposition of lignin and other substances.

Nucleus

It controls all the activities of the cell and was discovered by Robert Brown in

1831.

It consists of the following parts;

(1) Nuclear Membrane.

(2) Nucleoplasm or Karyoplasm.

(3) Nucleolus.

(4) Chromatin Network.

1. Nuclear Membrane

The nucleus is bounded by a double layered membrane which bears pores and is

known as “Nuclear Membrane”

2. Nucleoplasm

Inside the nuclear membrane is a structure less fluid called “Nucleoplasm” and

highly rich with proteins.

3. Nucleolus



It is a patch work of granules rich in R.N.A formed in the nucleus. They may be

more than one in a single nucleus. It contains mRNA formed from DNA, later

mRNA comes out of nucleus to control protein formation.

4. Chromatin Network

There is a network of threads dispersed in the karyoplasm called (Chromatin

network).

Each individual thread is called (Chromosomes).

These are made up of DNA and are carrier of genes.

Note: Types of Chromosomes from Book Page# 66)

Membrane Bound Organelles

(1) Endoplasmic Retuculum

It is a complex series of tubules in the cytoplasm. Endoplasmic reticulum is of

two types;

(1) Agranular or Smooth EPR.

(2) Granular or Rough EPR.

Smooth Epr

• It has no attached ribosome’s.

• Function is to synthesis lipid.

Rough Epr

• It has ribosomes attached to its outer surface.

• Synthesize protein and also transport material within the cell.

(2) Mitochondria

An oval body bounded by a double membrane. The inner membrane is folded to

form shelves/incomplete partitions. Which are known as “Crista”, here

oxidative enzyme is present. They are sites for aerobic cellular respiration and

the energy is produced. Therefore, also known as “Power house of cell”

(3) Golgi Apparatus (Dictyosomes)

These are thin, plate like structures and are usually located near the nucleus.

These are the site of formation of lysosomes and also conjugate protein, modify

structure of substances, synthesized by EPR to form lysosomes and secretary

vesides. Golgi bodies of plants and lower animals (mostly invertebrates) are

known as “Dictyosomes”.

(4) Lysosomes



They are large, somewhat irregular structure formed in the cytoplasm formed by

golgi-bodies. They contain hydrolytic enzymes which destroys foreign particles.

They are also known as “Suicide Sacs” because after secreting the enzymes they

digese their own proteins (Autophagy).

(5) Plastids

They are specialized organelles of plant cell that contain pigment or they

synthesize reserve substances.

They are of three kinds,

(A) Leukoplast

leuco = white

Leukoplast are colourless and store nutrient material.

(B)Chloroplast

Chloroplast are green having chlorophyll that performs photosynthesis.

(C) Chromoplast

Chromo = Colour

Chromoplast contain different coloured (red, yellow, orange or other than

green) pigments. They are found in the cells of different coloured flowers and

fruits.

(6) Micro Bodies

It includes peroxisome and glyoxysome.

(A) Peroxisome

These are the single membrane bounded microbodies contain enzymes for

transferring hydrogen atom to oxygen i.e. forming hydrogen peroxide.

• Hydrogen peroxide is very toxic to the cell therefore it is immediately break

down to water by enzyme catalyst.

• These microbodies help in detoxyfication of alcohal and mostly present in

liver cells.

(B) Glyoxysome

• It is a single layered membrane bound structure containing enzymes which

metabolize some molecules in photosynthesis and respiration.

• They also cause oxidation of fatty acids.

Cytoskeleton



Cytoskeleton means skeleton of the cell, which is mostly composed of

microtubules, microfilaments and intermediate filaments.

(A) Micro Tubules

• Microtubules are hollow cylinders with an outer diameter of 25nm.

• They are made up of a special type of globular protein tubulin.

• In single microtubule consist of hundredth of thousands of tubulin sub units,

which are usually arranged in 13 columns called Protofilaments.

• Microtubules are arranged in assemble and disassemble manner.

• In animal cells and lower plants, they also form centriole, cilia and flagella.

(B) Microfilaments

• Microfilaments are solid structures, thread like with a diameter of 7nm.

• They are also composed of globular proteins.

• Each microfilament consists of two actin (Protein) chains that inter wing in a

helical fashion.

(C) Intermediate Filaments

• They are intermediate in size having a diameter of 8nm to 11nm.

• They are rope like polymers of Fibrous protein.

• In skin and hair these filaments are made up of protein keratin.

• They provide mechanical strength to the cell and support the nuclear

envelope.

Non-Membrane Bound Cytoplasmic Orgenelle

(1) Ribosomes

• These are small structures concerned with protein synthesis in all type of the

cells i.e. Prokaryotic as well as Eukaryote.

• They are freely dispersed in cytoplasm of Prokaryotic cell but in Eukaryotic

cells they may be free or attached with endoplasmic reticulum.

• More than 50 type of proteins are present in ribosome structure and they

contain high quantity of RNA.

• Under the direction of Nucleus ribosome produce the protein made it by the

cell.

• Each Ribosome consist of two unequal parts.

• These are the smallest and most vital cellular components, manufactured in

the nucleolus.

(2) Centriole

They are only present in animal cells and certain lower plants.



Mostly near the nucleus.

Each centriole consists of two cylinders lying perpendicular to one another.

Each cylinder consists of nine parallel triplets of hollow cylindrical

microtubules.

During the cell division, they replicate and move towards opposite poles of the

cell.

In mitosis and meiosis, they form thread like fibers which radiate from each

centriole are known as mitotic apparatus.

(3) Vacuoles

• These are non-protoplasmic fluid filled cavities in the cytoplasm.

• Their membrane is known as Tonoplast.

• They are more prominent in mature cells.

• In plant cells vacuoles are filled with cell sap and act as store, house.

• They also play an important role in plant defence.

• In animal cells vacuole contain hydrolytic enzymes (i.e. lysosomes)

CHAPTER 5

VARIETY OF LIFE



Basis of Classification of Living Organisms

The living organisms are classified on the basis of Homology, comparative

Biochemistry cytology and Genetics.

(a)Homology

(b)Cytology.

(c)Bio-chemistry.

(d)Genetics

(A)Homology

The organisms placed in a particular group, all have many fundamental

similarities in their structure.

Example

The flipper, wing and arm are, all build on the same pattern but during the

course of evolution, each has been modified from its basic pattern to serve a

particular and usually highly specialized function, due to its adaptation different

to environment or habitate. (Structures that are similar because of their common

origin but may differ functionally is known as Homologus)

(B)Biochemistry

It is particularly useful, when we classify organism like bacteria, which may all

look alike and have an identical cellular structure with the help of

chromatography and electrophoresis we can compare the amino acid sequence

in the protein of different organisms or the order of bases in their DNA.

(C)Cytology

Microscopic observations of cell structure are also used to make a fundamental

split in the classification of living things. They can be useful at the level of

generic and species level. This sort of technique can show delicate difference

between species or sub-species, which are identical in many other respects.

Specie → Genus → Family → Order → Class → Division → Kingdom

(D)Genetics

All the morphological, Bio-chemical properties and cytological aspects of an

individual, or of a species depend on its genetic constitution. Hence the final

tool helping in classifying an organism is Genetics.

Taxonomic Hierarchy

The basic unit of the biological classification is specie. Closely related species

are grouped-together into Genera. Genera are grouped into Families, families



into order, orders into classes, classes into phyla and phyla or divisions into

kingdoms. Each grouping of organisms with in the hierarchy is called taxon and

each taxon has a rank and a name. For example, class “mammalia” or Genus

“Homo”. This ascending series of successively larger, more inclusive groups

make up the “Taxonomic Hierarchy”.

Changes Proposed by Marguiles and Schwartz in The Five-Kingdom

System

Marguiles and schwartz were American Biologist, put forward a modification of

Robert Whittaker’s scheme. According to this modification.

• The multicellular alga should be removed from the plant kingdom and

placed along with all unicellular organisms, in a new kingdom called

“Protoctist” which would replace Whittaker’s Protista kingdom.

• This modification made the plant kingdom a more natural group.

• Due to this modification, the kingdom Protoctista became a kingdom that

contains all those organisms, which cannot be fitted into any of the other

kingdom.

Virus:

Virus are very minute non-cellular bodies considered between living and non-

living organisms.

Discovery of Virus

The word virus is derived from a Latin word meaning “Poison”. A Russian

Biologist Iwanosky in 1892 discovered Virus.

Characteristics of Virus

1. Viruses are non-cellular parasitic entities (obligate parasite)

2. Viruses cannot live and reproduce outside the living cells because they lack

the machinery to do so by themselves.

3. The size of the viruses in range 20nm-250nm.

4. Viruses are either virulent destroying the cell in which they occur. While

temperate Viruses become integrated into their host genome and remain stable

for long period of time.

Structure of Virus

1. The viruses may be small sphere like or golf balls, like rod shape tadpole and

polyhedral.

2. They mainly consist of viral genome, capsids, envelopes and tail Fibers.



(A)Genome

Viral genomes may consist of a single or several molecules of DNA or RNA.

(B)Protein Capsid (Protein Core)

The protein coat that encloses the viral genome is called Protein capsid. It may

be of different shapes and mainly made up of proteins sub units called

“capsomeres”

(C)Viral Envelopes

In some viruses, accessory structure called Viral Envelopes are present that help

them in infecting their host. They are membranes that enclose the protein core.

Tails and Tail Fibres

Many viruses possess thread like long tail and tail fibers. These structures help

in infecting the host

Classification of Viruses

(A)On the Basis of Morphology

Viruses are generally classified on the basis of Morphology and nucleic acids

they contain. e.g. On the basis of morphology, Viruses are classified into rod

shape (TMV), spherical (Polio Virus) and Tadpole (Bacteriophage Virus).

(B) On the Basis of Modes of Origin

Viruses can be classified on the basis of their mode of origin, which provide a

systematic idea of some of their diversity. Following are the main

characteristics of these groups:

1. Unenveloped plus strand viruses.

2. Enveloped plus strand RNAViruses.

3. Minus strand RNA Viruses.

4. Viroids

5. Double strand RNA Viruses.

6. Small genome DNA Viruses.

7. Medium genome and large genome DNA Viruses.

8. Bacteriophage.

Life Cycle of the Bacteriophage

The virus that infects the bacteria (mostly E.coli) is known as “Bacteriophage”

Bacteriophage can reproduce by two alternative mechanisms.



1.The lytic cycle

2.The Lysogenic cycle.

(1) The Lytic Cycle

The life cycle of the bacteriophage that eventually ends in death of the host cell

is known as “A Lytic Cycle”.

The following are the stages of lytic cycle.

1. Initially the bacteriophage uses his tail fibers to stick to specific receptor

present on the outer surface of E-coli bacteria.

2. The sheath of the viral tail contracts, thrusting a hollow core through the

bacterial wall and membrane of the bacterial cell and then phage injects its

DNA into the cell.

3. The empty capsid of the phage is left outside the cell.

4. The bacterial cell’s DNA is destroyed (hydrolyzed).

5. The phage DNA takes control over the bacterial metabolic machinery and

uses it to produce phage proteins and viral nucleotide.

6. Copies of the phage genome are developed and different parts of the phage

come together forming daughter phages.

7. In the last stage of lytic cycle the daughter phages released, hydrolytic

enzymes “lysozymes”, which digest the bacterial cell wall.

8. Due to osmosis, bacterial cell swells and finally burst releasing 100-200

daughter phage particles.

2. The Lysogenic Cycle

The life cycle of the Bacteriophage in which the viral genome replicates without

destroying the host cell is known as lysogenic cycle.

Viruses that are capable of using both modes of reproduction with in a

bacterium are called “Temperate Viruses”.

The following are the stages of lysogenic cycle.

(1) In this cycle infection of the E-coli cell begins when the phage binds to the

surface of cell and injects its DNA.



(2) With in the host cell, the phage DNA molecule forms a circle.

(3) The DNA molecules of Viruses incorporated by genetic recombination into

a specific site on the host cell’s chromosome. Now it is known as “Prophage

cycle”

(4) The phage genome is mostly silent with in the bacterium.

(5) When E-coli cell prepares to divide, it replicates the phage DNA also, and

passes the viral copies to the daughter cells.

(6) This mechanism enables the virus to propagate without killing the host cell

upon which it depends.

At some point, prophage give rise to the active phages that lyses their host cells.

It is usually an environmental trigger such as radiations, or the presence of

certain chemicals that convert the virus from the lysogenic to the lytic mode.

Viral Diseases

1.Animal Diseases

(1) Poliomyelitis.

(2) Colds

(3) Encephalitis.

(4) Dengue fever.

(5) Yellow fever.

(6) AIDS

(7) Rabies.

(8) Measles.

(9) Mumps.

(10) Hepatitis.

2. Plant Diseases

(1) Tobacco Mosaic Virus (TMV) (Tobacco leaves disease) or (Tobacco Mosaic

Disease).

Aids

Causitive Agent

AIDS is stand for Acquired Immuno-Deficiency Syndrome, caused by Human

Immune Deficiency Virus (HIDV).



Symptoms

(1) Short flu like illness.

(2) Pneumonia like conditions.

(3) Disfiguring form of Skin Cancer (Kaposi’s Sarcoma)

(4) Weight loss and fever.

(5) Dementia (loss of thoughts)

(6) Diarrhea (loose motion with increasing frequency)

(7) Septicemia (Blood Poisoning)

Severity of the Immuno-Deficiency varies and bouts of illness may persist for

years.

HIV mostly infects lymphocytes and causes brain cell damage, in more than

50% of cases. Irreversible dementia and eventual death occurs.

Transmission

(1) The HIV virus can only survive in the body fluids and transmitted by blood

or semen.

(2) In 90% of cases the transmission occurs by sexual contact. Some other

modes of transmission are as follow:

• Unsterilized syringes and needles mostly in intravenous drug abusers.

• By giving blood or blood products already infected with HIV.

• Close contact between infected and non-infected people.

• From an infected pregnant woman to her baby through placenta or through

breast milk.

Control and Treatment

No particular drug is available for treatment of AIDS but there are some drugs,

which are effective against this disease like Azidothymadine, Zidovudine and

sumarin.

Prevention

• Use of the clean needles and sterilize syringes.

• Education and public awareness about the disease and restricted sexual

contacts with preventive measures.

• Tranfusion of screened blood and blood products.



Hepatitis

Hepatitis is an inflammation of the liver cells caused by viral infections, toxic

agents or drugs.

Signs and Symptoms

• Jaundice.

• Abdominal pain.

• Liver enlargement.

• Fatigue and fever.

Types of Hepatitis

There are various types of Hepatitis few of them are as follow:

(1)Hepatitis “A”

• Cause by non-enveloped RNA virus.

• Transmitted by contact with faeces from infected individual.

• Most common form of Hepatitis worldwide.

(2)Hepatitis “B” (Serum Hepatitis)

• Caused by DNA viruses.

• More common in Asians, Africans and male homosexuals.

• Often persist in carrier form without causing any symptoms.

• Transmission mostly occurs through skin contacts, blood transfusion and

other medical procedures. (Surgery, NG tube, Catheters)

• The virus of this disease can cause liver cancer mostly in carriers.

Treatment and Prevention

• New vaccines against the virus have been produced which are of great

importance especially for person who required frequent blood transfusion.

(3)Hepatitis “C”

• Transmission occurs through mother to child during pregnancy.

• By sexual contacts.

• Most common transfusion associated Hepatitis.

• It causes liver cancers more often than HBV.

CHAPTER 6

THE KINGDOM (MONERA)

Bacteria:

Discovery

Bacteria was discovered by A.V. Leuwenhoek in 1676.



Structure of Bacteria

Bacteria are smallest and simplest living organism measures from 0.2m to 2

microns in breadth and 2 to 10 microns in length. They are strictly unicellular

but some species remain associated with each other after cell division and form

colonies.

A generalized bacterial cell consists of following structures.

(1)Flagella

They are extremely thin appendages, which originate from basal body, a

structure in the cytoplasm beneath cell membrane. Flagella help in bacterial

locomotion.

(2) Pilli

They are hollow, filamentous flagella like appendages, which help in

conjugation but not in locomotion.

(3) Capsule

It is a protective sheath made up of polysaccharides and proteins. It provides

greater pathogenicity and protects bacteria against phagocytosis.

(4) Cell Wall

Bacterial cell wall mostly made up of amino acids, sugar and chitin. It surrounds

the cell membrane, determine shape and protects bacteria from osmotic lyses.

Most bacteria have a unique macromolecule called Peptidoglycan in addition to

it. Sugar molecules, teichoic acid, glyco proteins and lipo polysaccharide are

also present.

(5) Cell Membrane

• It is present inside the cell wall attached to it at few places containing many

pores.

• It is made up of lipids and proteins.

• It acts as a respiratory structure.

(6) Cytoplasm

Bacterial cytoplasm is granular containing many small vacuoles, glycogen

particles and ribosomes.

(7)Mesosomes

• These are the invaginations of the cell membrane into the cytoplasm.



• They are in the form of vesicles, tubules or lamella.

• They help in the DNA replication, cell division, respiration and export of

enzyme.

(8) Bacterial Hereditary Material

• Bacterial hereditary material DNA is found as concentrated structures called

Bacterial chromosomes or chromatin bodies. It is mostly scattered in the

cytoplasm.

• A small fragment of extra chromosomal circular DNA, called Plasmid is also

present.

Classification of Bacteria

On the Basis of Shape

On the basis of shape bacteria can be divided into four categories.

(1)Cocci

• These are spherical or rounded bacteria presents in the form of mono, diplo

or streptococcus form.

• They are non-flagellated and cannot move from one place to another place.

(2)Bacilli

• Bacilli are rod shaped bacteria, can be present in the form of diplo or

streplobacilli.

• They may be flagellated and can move from one place to another.

(3)Spirilla

• These are spiral or cork, screw shape bacteria also known as spirochetes.

• It includes chlamydia and rekettia.

(4)Vibrio Or Comma

• These are slightly curved bacteria like vibrio cholera.

• They may be flagellated and can move.

On the Basis of Respiration

On the basis of respiration bacteria can be divided into two main types.

(1)Aerobes

Require oxygen for respiration.

(2)Anaerobes

Respire without oxygen



Sub-classes of this classification are as follow:

(A)Facultative Bacteria

Respire with or without oxygen.

(B)Micro Aerophilic Bacteria

Require low concentration of oxygen for growth

(C)Obligate Anaerobes

These bacteria only survive in absence of oxygen.

(D)Facultative Anaerobes

These bacteria use oxygen but can respire without it.

(E)Obligate Aerobes

These bacteria only survive in the presence of oxygen.

On the Basis of Nutrition

Bacteria can be divided into four main types on the basis of nutrition. Which are

as follow.

(1)Saprotrophic Bacteria

• These bacteria depend on the dead organic matter for their nutrition.

• They are mostly present in the humus of soil and possess large number of

enzymes that convert complex substances of humus to simpler compounds.

(2)Symbiotic Bacteria

• These bacteria are found associated with another living organism.

• They obtain their food from the host without harming it. E.g. Rizobium

redicicola (Symbionts in the root nodules of pea family plants).

(3)Parasitic Bacteria

• These bacteria grow inside the tissues of another living organism

• They obtain food at the expense of their host.

• These bacteria lack certain complex system of enzymes therefore they

usually depend upon host cell. E.g. Pneumococcus, Mycobacterium

tuberculosis, Salmonella typhi.

(4)Autotrophic Bacteria

• These bacteria can sythesize organic compound from simple inorganic

substances.

Autotrophic bacteria can be divided into photosynthetic or chemosynthetic.



(A)Photosynthetic

• These bacteria contain green pigment chlorophyll, which is known as

bacterial chlorophyll, or chlorobium chlorophyll.

• These pigments are present in mesosomes (invagination of the cell

membrane in the cytoplasm)

• These bacteria utilize H2S during photosynthesis instead of water and

liberate Sulphur instead of oxygen.

(B) Chemosynthetic

• These bacteria obtain their energy from oxidation of some inorganic

substances like iron, hydrogen, nitrogen and sulphur compounds.

Locomotion in Bacteria

• Some bacteria can move from one place to another with the help of a wipe

like structure flagella.

• Flagella allow bacteria to disperse into new habitats, to migrate towards

nutrients and to leave unfavorable environment.

• Flagellated bacteria show orientation towards various stimuli, a behavior

called Taxis.

• Some bacteria are chemo tactic, phototectic or magnetotatic.

Growth in Bacteria

In favorable conditions bacteria, can grow, very rapidly. There are some factors

affecting growth of bacteria such as Temperature, nutrient availability, PH and

ion concentration. Bacterial growth can be divided into four main phases, which

are as follows;

(1)Lag Phase

It is inactive phase during which bacteria prepare them for division.

(2)Log Phase

In this phase bacteria grow and multiply very rapidly.

(3)Stationary Phase

In this phase, bacterial multiplication is equal to bacteria death rate.

(4)Decline/Death Phase

In this phase death is more rapid then multiplication rate.

Reproduction in Bacteria

Usually, asexual reproduction is present in bacteria which is as follow



Fission

Fission is the fastest mode of bacterial asexual reproduction (Binary Fission)

• It usually takes place in favorable conditions.

• Hereditary material DNA in the form of chromatin body replicates.

• After the replication of hereditary material, a constriction appears in the

middle of the cell, which later splits it into two parts.

• Newly form bacterial cells grow in size and form nature bacterial cells.

• The single fission takes place in 20-30 minutes.

Endospore Formation

• It is the method of bacterial survival under unfavorable conditions.

Following are the main characters of this process.

• During this process, the whole protoplasmic content gets shrink into a small

mass.

• A cyst is formed inside the parental wall around constricted protoplasm to

form endospore.

• On the return of favorable conditions parental wall raptures due to decay and

endospore is set free.

• In the end, this endospore enlarges to form a mature bacterial cell.

Genetic Recombination in Bacteria

Genetic changes with the help of which bacteria adopt new characteristics

(drugs resistance pathogenic ability) is known as Genetic recombination

Three types of genetic recombination are present in bacteria, which are given as

follow.

1.Conjugation

Simple process of genetic recombination in which genetic material is transferred

from one bacteria to another through a conjugating tube. Conjugation in bacteria

was discovered by Joshua Lederburg and Edward L.Tatum in 1946

Experiment

J.laderberg and E.Tatum performed an interesting experiment in order to prove

conjugation in bacteria. Following are the main steps of this experiment.

1. They selected a wild type bacteria (E-coli) and obtain (triple nutritional

mutants) different from one another.

2. Wild-type was capable of synthesizing six substances symbolized as A, B, C,

D, E and F.



3. Mutant type I was capable of synthesizing three substances symbolized as A,

B and C but not D, E and F.

4. Mutant type II was capable of synthesizing three substances D,E and F but

not A,B and C.

5. These mutant type I and II were grown together in the growth medium having

all the six substances A, B, C, D, E and F.

6. After several hours, three types of bacteria were detected after nutritional test

which were,

i. Both mutant I and mutant II types.

ii. Wild type bacteria synthesizing all the six substances.

iii. A new type of bacterial strain requiring all the six substances for growth.

In this experiment, appearance of wild type and one new type is an evidence

that conjugation had taken place.

2. Transduction

It is the mode of genetic recombination in which genetic material is transferred

from one bacteria to another by a third party, which is usually bacteriophage.

This process was experimentally carried out by Lederberg and Zinder in 1952.

Experiment

1. In this experiment, a bacteriophage is made to attack a bacterium known as

“donor” (D).

2. The injected DNA of bacteriophage multiply to form a large number of

daughter phages.

3. The donor bacterium (D) gives some of its genetic material “D” to the

multiplying particles.

4. The phages released from this donor bacterium contain the genetic material of

phage plus a little piece of the donor genetic material “D”.

5. These new phages then made to attack a new bacterium known as

“Recipient” (R).



6. These recipient bacterium is not destroyed like the donor in order to

reproduce normally. In this way, genetic material of the donor bacterium is

carried to the recipient bacterium by a bacteriophage and this process is known

as Transduction.

3. Transformation

• In this process, genetic information transfers from one bacteria to another by

producing a change it (undergo a change).

• This type of genetic recombination was first proved by Fred Griffith in 1928.

Experiment

• Griffithi injected a small quantity of R-type bacteria and a large quantity of

heat killed S-type bacteria into the same mouse.

• This treatment proved fatal as mouse surprisingly suffered from Pneumonia

and died.

• The autopsy of the mouse revealed the presence of living S-type bacteria in

the mouse in addition to R-type.

From this experiment, Griffith concluded that,

• The live R-type bacteria had been transformed into live S-type bacteria due

to transfer of some material from dead S-type, cells.

• Thus, this transformation occurred due to genetic recombination in R-type

bacteria.

In his experiment, he had been working on two strains of bacteria

“Pnemococcus”. One strain is known as smooth type (Virulent and causes

Pneumonia) while the second strain is known as (Rough type (Non-Virulent and

does not cause pneumonia).

Vaccination:

Definition

Inoculation of host with inactive or weaken pathogens or pathogenic products to

stimulate protective immunity.

• In case of subsequent natural infection with the same pathogen the immune

system easily recognized the invader and comfortably managed to overcome

the pathogen.

• A vaccine can take orally (Polio vaccine) or injected into the body (Tetanus

Vaccine).



Immunization

Definition:

It is a process of induction of specific immunity by injecting antigens,

antibodies or immune cells.

• Immunity can be protective or curative in nature.

• It promotes increased immunity against specific diseases.

Cynobacteria (Blue Green Algae)

Main Characteristics of Cynobacteria

• They are prokaryotic unicellular autotrophic organisms mostly occur in

colony form.

• They possess double layered cell wall.

• The protoplasm differentiated into an outer colored region chromoplasm,

which contain various pigments in which chlorophyll “a” and phycocyanin

are more important.

• Inner colorless region of the protoplasm is known as centroplasm.

• They are mostly aquatic (fresh water)

• Sexual reproduction is absent.

• Asexual reproduction takes place by means of Harmogonia, zoospores,

akinates and fragmentation.

Nostoc

• Nostoc is a typical example of blue green algae.

Structure

• Nostoc is some filamentous prokaryotic algae in which filaments are

intermixed in a glatinous mass-forming ball like structure known as

coenobium.

• A single filament look like a chain of beads.

• Each filament is unbranched and has a single row of rounded or oval cells.

• Each cell has double layered wall, outer thick wall is made up of cellulose

mixed up with pectic compounds. While inner thin layer is made up of

cellulose only.

• The protoplasm is differentiated into an outer colored region (chromoplasm)

and an inner colorless region (centroplasm).

• The chromoplasm various pigments like chlorophyll, axanthophylls,

carotene, phycocyanin and phycoerythrin.

• Ribosome’s, pseudovacuoe and reserve food in the form of cynophyceae

starch are present.



• Hereditary material is present in cytoplasm without the nuclear membrane.

• In Nostoc filaments slightly larger, colorless cells with thick walled known

as “Heterocyst” are present. The function of Heterocyst is nitrogen fixation,

food storage and multiplication of filament during unfavorable conditions.

Nutrition

• It is an autotroph and prepares its food in the presence of sunlight.

• It also capable of fixing atmospheric nitrogen and converts it into nitrates in

order to prepare amino acids and proteins, this activity takes place in

Heterocysts.

Reproduction

• Only asexual reproduction is present which takes place by following

methods.

(1)Hormogonia

• A portion of the filaments between two heterocysts is known as

Hormogonia.

• During favorable conditions, filaments break up at the junction of each

Heterocyst.

• The end cells of each homogonous divide to form long filaments of Nostoc.

(2)Akinetes

• It is the method of survival during unfavorable conditions.

• These are non-motile spores, formed from certain vegetative cells.

• Each akinete contains an outer layer “exospore” and inner layer

“endospores”.

• On the return of favorable conditions, each akinete germinates by rupturing

exospore and formed independent filaments by simple cell division.

Importance of Cynobacteria

• They release oxygen as a by-product during photosynthesis.

• Many are capable of fixing atmospheric nitrogen.

• They are first colonizers of moist soil.

• Nostoc anabena is used as nitrogen fertilizer in agriculture due to its nitrogen

fixing ability.

Monera

• Discovery of bacteria A.V.Leuventoek.

• Size of bacteria = 0.2-2 micron (breadth)

• = 2-10 micron (length).

• Cell wall of bacteria made up of peptidoglycan.



• Arch bacteria do not contain peptidoglycan.

• Bacterial replications, cell division, respiration, export of enzymes = By

means of mesosomes (invaginations of cell membrane)

• Saprophytic bacteria form humus (important component of soil)

• Photosynthetic bacteria = use H2S in photosynthesis instead of water.

• Chlorobium chlorophyll or bacterial chlorophyll discovered by Von Nell

1930.

Diversity of Life

• Father of taxonomy = Charles Linneus.

• Genetics = final tool in classifying living organism.

• Basic unit of Biological classification = species.

• Five kingdom system of Robert Whittaker = 1969.

• Discovery of Virus = Iwanosky 1892.

• TMV Virus discover by Wendell Stanley in 1935.

• Size of Virus = 20nm-250nm.

• AIDS is caused by Human Immune Deficiency Virus (HIV)

• As a result of lytic cycle of bacterio phage 100-200 daughter phage viruses

are produced.

CHAPTER 7

THE KINGDOM PROTISTA

Plant Like Protoctista

Ulva: (Sea-Lettuce)

Occurance

• Ulva, commonly called Sea Lettuce, is a marine green alga.



• It is found attached to rocks, along the sea coast in intertidal zones (the area

between the high tide and low tide mark)

• In Karachi, it is found on Manora coast.

Structure

• Ulva exhibits primitive simple multicellular organization.

• The plant body is a thallus, which is flat, erect, wrinkled and sheet like

structure having a length of about 30 cm (1ft).

• The thallus is very thin and internally it is composed of two vertical rows of

cells only.

• Its lower part forms a “hold fast”, consisting of long thread like cells for

attachment to the substratum.

Reproduction

Ulva can reproduce sexually as well as asexually.

(1)Sexual Reproduction

• Sexual reproduction is isogamous and takes place in sexual plants or

gametophyte, which are haploid (n).

• Each cell of the gametophyte produces many biflagellate gametes, which are

released in seawater.

• The gametes are morphologically similar or isogametes but the fusion takes

place between gametes produce by two different gametophyte plants, which

are termed as positive strain and the negative strain.

• Thus, ulva plant exhibits heterothallism (two type of plant body i.e.

gametophyte (n) and sporophyte (2n) ulva).

• After fusion, a diploid quadri flagellate zygote is formed.

• Zygote swims for some time then loses its flagella, secretes a wall around

itself and undergoes a period of rest.

• Finally, the zygote germinates and develops into a new diploid ulva plant,

which is called asexual plant or sporophyte.

(2)Asexual Reproduction

• Asexual reproduction takes place by formation of quadri flagellate zoospores

in diploid asexual plant or sporophyte, which is morphologically similar to

gametophyte.

• Each cell (except the basal cells) of the sporophyte (2n) undergoes meioses

or reduction division and forms 8-16 zoospores, which are released in water.

• After swimming, they lose flagella and undergo a period of rest.



• Each zoospore ultimately develops and forms haploid sexual plant i.e.

gametophyte, thus completing the life cycle.

Alternation of Generation

A distinct regular alternation of generations between the haploid gametophytes

(sexual plant) and diploid sporophyte (asexual plant) is present. Since the two

plants are morphologically similar so this process is known as “Alternation of

generation (isomorphic)”

Chlorella

Occurance

• Chlorella is a fresh water alga found floating in stagnant water of ponds,

pools and ditches.

• It is easily cultured and has been used an experimental organism in research

in photosynthesis.

Structure

• The body of chlorella is one celled, spherical in outline and solitary.

• It contains a single nucleus and a cup-shaped chloroplast usually without

pyrenoid.

Reproduction (Asexual Reproduction)

• Reproduction takes place by aplanospore formation, which involves the

division of protoplast into 8-16 daughter protoplast.

• Each daughter protoplast secrets a wall to produce a non-motile aplanospore.

• On release from the parent cell, each aplanospore forms a new vegetative

cell.

Importance

Recently an antibiotic known as “Chlorellin” useful for the control of bacterial

diseases has been prepared from the plant.

Fungi Like Protoctista

Slime Mold (Plasmodium Stage)

• In initial stages of life cycle, slime mold are creeping masses of living

substances, having the consistency of an unboiled egg white and the colour

of the yolk.



• It sends out protoplasmic arms that engulf and digest bacteria from the

surface of rotten rock or leaves.

• This amoeboid stage of slime mold is called plasmodium stage.

• The plasmodium consists of the cytoplasm in which are embedded many

nuclei, food vacuoles and undigested food particles.

• Plasmodia can move along the forest floor, on to dead leaves that are bathed

in sunlight.

Fruiting Body

• In dry warm environment metamorphosis in Plasmodia takes place and it

changes into cluster of fruiting bodies.

• Depending on the species the fruiting bodies look like golf balls, feathers,

bird cages or worm like and in a great variety of colours.

Reproduction

• Each fruiting body produces a large number of microscopic asexual

reproductive cells known as spores.

• Each spore has a single nucleus and a thick protective wall.

• Germination of the spore occurs when there is plenty of water and suitable

temperature.

• When a slime mold’s spore germinates, it produces one or more tiny cells.

• Each cell has a pair of flagella that propel it through the film of water, which

is necessary for its germination.

• These flagellated cells sometimes function as gametes (sex cells) and fuse in

pairs. This is true sexual reproduction.

• Fusion of the gametes forms zygote, which become amoeboid and form a

new plasmodium i.e. multinucleated slime mold

Phytopthora Infestans (Water Mold)



• These fungi like protoctist belongs to family Oomycotes.

• It is a pathogenic organism causing. “late blight of potato”

Structure

• The mycellium consist of Hyphae which are endophytic, branched, aseptate

coenocytic, hyaline and nodulated.

• The rounded or branched hustoria are found which absorb food material

from the host cells.

Reproduction

Sexual as well as asexual reproductions are present.

(A)Asexual Reproduction

• Asexual reproduction takes place by means of biflagellate zoospores produce

inside the productive structure Sporangia.

• The spores are produced on the branched Sporangiophore in favorable

condition.

• Sporangiophore coming out through the stomata, in groups on the lower

surface of infected leaves.

• The sporangia are produced on the branches of sporangiophore.

• On maturation, the sporangia the detached from sporangiophore.

• On maturation, the protoplasm of the sporangium converts into uninucleate,

vacuolated and naked zoospores.

• When mature sporangium burst, the zoospores liberate in the film.

(B)Sexual Reproduction

• Sexual reproduction is zoogamous.

• The female sex organ is oogonium. while the male sex organ is antheridium.

• The antherialium develops first and the oosgonium later.



• Both sex organ may develop on the same Hyphae or on two adjacent Hyphae

lying side by side.

• The oogonium hyphae penetrates the antheridium.

• The oogonium is pear shaped and contains a single female nucleus in it.

• The fertilization takes place when the male and the female nuclei fuse in the

egg after penetration of the oogonium in the antheridium.

• There is no fertilization tube and after fertilization the thick-walled zoospore

developed, which is present inside the oogonium.

• The oospore germinates in favorable conditions and produce new mycellium.

• Reduction division occurs during germinates of oospore.

Economic Importance

• The Water Mold causes a disease in potato crop known as “late blight of

potato”

• This disease effects both aerial and underground parts and whole plant

becomes blighted in severe conditions.

• The disease appears in the form of brown spread patches on leaves and

rapidly increases to the whole leaf surface.

• The tuber converts into a rotten pulpy mass emitting foul smell and remains

small in size.

• A great danger to potato crop and causes sufficient damage of Potato crop.

Euglena

Euglena is a unicellular, flagellated organism. It belongs to the division

“Euglenophyta”

Occurance

Euglena commonly found in drains, ponds and is also present in soil, blackish

water and even salt water.



Duel Nature

• Euglena has characteristics of both animals and plants.

• It is more evolved than green Algae.

Structure

1. It is somewhat elongated animal, almost pointed at both ends.

2. It has definite and easily stainable nucleus.

3. It has well defined chloroplast as in higher plants.

4. All the Euglena have two flagella usually one of them is long and the other

one short by which they can swim activity.

5. They lack the outer cellulose cell wall, instead the protoplasm is bounded by

a grooved layer called the “Pellicle”.

6. Euglena has a gullet near the base of the flagella and an eyespot containing a

pigment called “Astaxanthin”.

7. Reproduction is usually asexuality by simple division.

Taxonomic Position of Euglena

• One of the examples of Eukaryotes is Euglena.

• Belongs to group kingdom Protactista.

Plant Like Characters in Euglena

1. Presence of Chloroplast.

2. Undergoes physiological, biochemical process of photosynthesis.

3. Behaves as natural autotroph in presence of sunlight.

Animal Like Characters in Euglena

1. Absence of a cell wall.

2. Presence of a mouth with cytopharynx.

3. Eyespot containing animals pigment called “Astaxanthin”.

4. Presence of reservoir.



5. Can easily be converted into heterotopy after the loss of chloroplast.

Animal Like Protoctista

Phylum Protozoa

General Characters

1. Protozoa are microscopic, unicellular (as single cell performs all vital

activities) organisms.

2. These organisms are asymmetrical.

3. The body of organism may be naked or covered by pellicle to maintain the

shape.

4. Cytoplasm of protozoans is usually divided into outer, ectoplasm and inner

granular endoplasm.

5. Cell may be uninucleate or multinucleate. Nuclei are covered by nuclear

membrane.

6. Protozoan may be solitary or colonial.

7. They are aquatic and are found in both fresh and marine water.

8. Nutrition may be holozoic (animal like), halophytic (plant like) or saprozoic

(subsisting in dead organic matter) or parasitic.

9. Digestion is intracellular and is accomplished inside the food vacuole.

10. Locomotion takes place by flagella, cilia or psendopodia.

11. Respiration takes place through general body surface.

12. One or more contractile vacuoles are present for osmo-regulation.

13. Reproduction takes place by both asexual and sexual methods.

14. The asexual methods include binary fission, multiple fission and budding.

15. Sexual reproductive methods include gamete formation (Isogamies and

Anisogamous) or by conjugation.

Classification



About 30,000 species of protozoa are divided into five classes, which differ in

their means of locomotion.

1. Class flagellate (Mastigophora).

2. Class sarcodina (Rhizopoda).

3. Class ciliate (Ciliophora).

4. Class suctoria.

5. Class sporozaa.

(1)Class Flagellata

1. Locomotary organs are long hair like “Flagella” with are one or two in

number.

2. Body is enclosed in a thin covering of “Pellicle”.

3. Asexual reproduction takes place by longitudinal fission.

4. Class Flagella is divided into sub classes.

(A)Sub-Class Phytoflagellata (Phytomastigma)

• Contain chlorophyll and perform process of photosynthesis.

• Examples: Euglena and Volvax.

(B)Sub-Class Zooflagellata (Zoomastigma)

• Does not contain chlorophyll and are heterotrophic.

• Examples: Trypanosome and Leis mania.

• Some flagellates are parasites. For example: Trypanosome is a blood parasite

human and causes African sleeping sickness. Its carrier is “Tse Tse fly”.

(2)Class Sarcodina (Rhizopoda)

1. Locomotion takes place by “Psendopodium”.

2. Body shape is not definite and keep on changing because the pellicle is

absent. Some have external sheats or skeletons.

3. Nutrition is mostly holozoic, some are parasite. E.g. Entamoeba, histolytic

can cause human dysentery.

4. Example:



i. Entamoeba histolytic is a parasite living in intestine of man. ii. Foraminifera is

a group including shelled sarcodimians. E.g. Polystomella. iii. Heliozoa is a

group including fresh water organisms having fine, stiff and ray like

psendopodia e.g. Actinophrys.

(3)Class Ciliata

1. Locomotory organs are cilia which are short, thin, protoplasmic structure,

covering the body surface.

2. Body shape is definite and maintained by pellicle.

3. Many ciliates have a groove or depression called “Gullet” into which food

can be brought.

This class is divided into two sub-classes.

(I) Sub-Class Protociliata

• Cilia all of equal size and uniformly distributed.

• Cytosomes absent.

• Nuclei two to many but all of one type e.g. Opalina

(II) Sub-Class Enciliate

• Cilia of different types and not uniformly distributed.

• Cytosomes usually present.

• Nuclei of two types types Micronucleus and Meganucleus e.g. Paramecium,

Balantidium.

(4)Class Suctoria

1. They are closely related to ciliates; therefore, both are including in same sub-

phylum i.e. sub phylum Ciliphora.

2. Young individual have cilia and swim about but the adults are sedentary and

have stalks by which they are attached to the substrate.

3. Body bears a group of delicate cytoplasmic tentacles, some of which are

pointed to pierce their prey, whereas others are tripped with rounded adhesive,

knobs to catch and hold the prey.

4. The tentacles secrete a toxic material which may paralyze the prey.

5. Suctorians have two nuclei i.e. meganucleus and micronucleus.



6. Reproduction is by asexual budding. E.g. Acineta, Ephelota.

(5)Class Sporozoa

1. All are parasites.

2. Lomotary organs are absent.

3. Body covered by a thick cuticle.

4. Asexual reproduction is by multiple fission or sporulation.

5. Sexual reproduction is isogamies or anisogamous.

6. Examples.

i) Plasmodium is a human blood parasite enters the human blood when an

infected female Anopheles mosquito bites humans. Plasmodium reproduces

asexually in man and sexually in the body of mosquito.

ii) Monocytis lives as some parasites in seminal vesicles of earthworm.

Malaria:

Introduction

“Malaria is an infectious disease marked by attacks of chills fever, sweating

occurring at intervals that depends on the time required for the development of a

new generation of parasites in the body”.

Causative Agent

Malaria is caused by a protozoan parasite of the genus Plasmodium. It was

discovered by Laveran in 1878.

Transmitting Agent

Malaria is transmitted into the blood of man by the bite of an infected “Female

and Pheles Mosquito”. It was discovered by KING in 1717.

Symptoms of Malaria

The symptoms of malaria first appear after several days of infection in man. He

time taken by parasite before it appears in the blood is called Incubation Period.

Symptoms During Incubation Period

The symptoms that appears in incubation period:

• Nausea.

• Loss of appetite.

• Constipation.



• Insomnia.

• Headache.

• Muscular pain.

• Aches in joint develops.

Usual Symptoms of Malaria

• Onset of malarial fever

• Shauking chills

• Sweating

• Rise in body temp. (may be up 106˚)

Malaria – A Biological Problem

Malaria has been one of the man’s most important biological problems. Millions

of people have been killed only because of his disease. To solve this problem,

various biological methods were applied to find out in details. Experiments

were performed, observation and data were collected, and finally the complete

life cycle of the malarial parasite was studied.

Studying Malaria Experimentally

In the experimental study of malaria, several Hypothesis were presented and

deductions were made for each of them. Experiments were performed to test the

deduction and observations are recorded. If the deductions are proved true, the

hypothesis regarded as correct.

Hypothesis (1)

A hypothesis was made about the malarial parasite plasmodium that:

“Plasmodium is the cause of malaria”

Deduction To test the above hypothesis, the following deductions were made: “If the

plasmodium is the cause of malaria, then the patients suffering from malaria

should have malarial parasite in their blood”.

Experiment

Experiment were carried out by examining blood samples from malarial patients

that showed positive result. To prove it further experiments were repeated

whenever malaria accured.

Result

In this way, the hypothesis that the “Plasmodium is the cause of malaria” was

found to be true.



Hypothesis (II)

It was noted that people living around the marshy places were usually have the

attack of malaria. Thus, the hypothesis was stated “Malaria is associated with

marshes”.

Deduction

To test the statements, a deduction was made that “If marshes are eliminated”.

Experiment

On experimental basis, marshes were eliminated and as a result the role of

infection of malaria was greatly much reduced.

Result

It was this proved that malaria is associated with marshes. Thus, the hypothesis

stands true. Thus, it is new understood that accurate methods are essential to

understood biological problems.

Life – Cycle of Malarial Parasite

Discovery

Life cycle of plasmodium in Anopheles Mosquito was first discovered in 1898.

Phases of Life Cycle

The life cycle of plasmodium is digenetic involving two phases is two hosts for

completion.

1. Asexual Phase in Man (Primary Host)

2. Sexual Phase in Mosquito (Secondary Host)

Asexual Cycle In Man (Schizogony)

Introduction

The life cycle of plasmodium in mass is Asexual and is called Schizogony,

because “Schizonts” are produced.

Phases of Schizogony

According to Graham (1948), the life cycle of plasmodium can be divided into

four phases;

1. Pre-Erythrocytic Phase (Liver Schizogony).

2. Erythrocytic Phase.

3. Post-Erythrocytic Phase.



4. Gamorony or Gametocytic Phase.

Explanation of Schizogony

Infection

A healthy person acquires infection when a female Anopheles mosquito,

containing infective stages (Sporozoites) of parasite is its salivary gland, bites

him for sucking his blood.

(1) Pre-Erythrocytic Phase

Once with in the human blood, the sporozoites circulate in the blood for about

half an hour.

Invasion of Liver

After circulation in the blood, the sporozoites get into liver to invade the hepatic

cells.

Schizont Formation

After penetrating the liver cells, each sporozoite grows for number of days and

becomes a Schizont.

Cryptozoite Formation

Schizont divides to form a large number of uninucleate Cryptozoites, which are

liberated when the liver cell burst.

Metacryptozoite Formation

The released cryptozoites invade the fresh liver cells and multiply producing

enormous no. of metacryptozoites.

(2) Erythrocytic Phase

Trophozoite Formation

The metacryptozoites after escaping into the blood stream, invade the red blood

corpuscles. Each become rounded and is called Trophozoite.

Signet Ring Stage

When trophozoite grows in size, the nucleus is pushed to one side into the

peripheral cytoplasm. It resembles a signet ring and is preferred to a Signet

Ring Stage.

Merozoite Formation

The trophozoite ingesis a large amount of cytoplasm of the R.B.C. The blood H6

is broken down into its protein components, which is used by trophozoite

develops into an active amoeboid trophozoite. After active feeding, it becomes



rounded and grows in size and become and Schizont. It now undergoes

Schizogony and produces Merozoites.

Release of Merozoites in Blood

With the rupture of RBC’S, the merozoites are liberated into the blood plasma.

These invade fresh corpuscles to repeat the cycle. The time taken to complete

one erythrocytic cycle depends upon the species of Rasnodium.

(3) Post-Erythrocytic Phase

Some merozoites produced in erythrocytic phase reach the liver cells and

undergo schizonic development. This is known as Post-Erythrocytic Phase.

(4) Gamogony

Formation of Gametocytes

When successful asexual multiplication is achieved, the merozoites do not

proceed further with the erythrocytic phase but, after entering the RBC, increase

in size to form Gamocytes.

Types of Gametocytes

Gametocytes are of two types:

1. Male Microgamo Cycle

2. Female Macrogamo Cycle

The Gametocytes do not divide, but remain within the host blood until they are

injected by the vendor, in which they continue their sexual development.

Sexual Cycle in Mosquito

Introduction

Sexual life cycle of Plasmodium is completed in the gut of Female Anopheles

Mosquito resulting in infective Sporozoites. This cycle is completed in 12-23

days.

Phases of Sexual Cycle

This cycle comprises of following stages:

1. Gametogony

2. Syngamy or Fertilization

3. Sporogony

Explanation of Sexual Cycle

(1) Gametogony

Gametogony refers to the Formation of Gametes. The gamocytes are taken up

along with the blood into the stomach of the mosquito and develop into

gametes.



Female Macrogamete

The female gamocytes soon become macrogamete, which is larger in size and

ready to fertilize.

Male Microgamete

Each male gamocyte forms 6 to 8 sperms like microgametes by a process of

Exflagellation.

(2) Syngany Or Fertilization

Zygot Formation

Within the gut of mosquito, the two gametes of opposite sexes fuse together to

form a zygot. This process is called Syngamy.

Okinete Formation

After fertilization zygot differentiates into motile worm-like ookinete.

Oocyst Formation

Ookinete penetrates the stomach wall to settle down just under the mid gut.

Here after observing nutrients, it develops a cyst around it and becomes

spherical. This encysted is called Oocyst.

(3) Sporogony

The oocyst then enters a phase of asexual multiplication, the Sporogony.

Sporoblast Formation

In 6 to 7 days, the nucleus of oocyst divides into several nuclei and cytoplasm

envelops each one of them and thus hundreds of oval shaped Sporoblasts are

formed.

Sporozoite Formation

The sporoblast nucleus again divides and forms hundreds of filamentous,

uninucleated Sporozoites. The cyst bursts and liberated sporozoites migrates to

the Salivary Gland where they await to penetrate to a human host.

CHAPTER 8

THE KINGDOM FUNGI

Kingdom Fungi

“Fungi are a group of unicellular to multicellular, thalloid, heterotrophic,

eukaryotic living organisms having a body called Mycellium, made up of

HYPHAE which are non-chlorophyllous & have cell wall (made up of chitin).

Reproduction is usually Asexual by means of spores”.

Fungi are neither Completely Plants nor Animals



Previously fungi were regarded as plants as they resemble the plants in many

characteristics. But in addition, fungi have many qualities just like the animals.

So, they are regarded in the midway between plants and animals.

Plant Like Characteristics of Fungi

Fungi resemble the plants in

• Having Cell Wall

• Lacking Centrioles

• Being non-motile

Animal Like Characteristics of Fungi

But Fungi also resemble with animals as they are

• Heterotrophic

• Lack cellulose in their cell wall

• Presence of chitin

It means that; Fungi are neither completely plants nor animals.

Confirmation

Detail studies also confirm that Fungi are different from all other organisms.

Nuclear Mitosis

They have a characteristic mitosis called Nuclear-mitosis, during which nuclear

membrane does not break & spindle is formed with in the nucleus.

Some Representatives of Kingdom Fungi

Some imp. Examples are as follows:

• Yeast

• Mushrooms

• Penicillium

• Mold

• Mucor

• Rhizopus

Structure of Body of Fungus

Mycelium

The complete multicellular body of fungus is called Mycelium, which is

composed of white fluffy mass of branched hyphae.



Hyphae

A few of true fungi are unicellular (such as yeast) but most have multicellular

body (mycelium) consisting of long, slender, branched, tubular, thread like

filaments called as Hyphae which spread extensively over the surface of

substrate.

Hyphae

Types of Hyphae

Hyphae can be divided in to two types:

1. Septate or Multicellular Hyphae

2. Non-septate or multinuclear or coenocytic hyphae.

1.Septate Hyphae

Definition:

“Those hyphae which are separated by cross-walls called “septa” into individual

cells containing one or more nuclei, are called “Septate Hyphae”

Example: Mushrooms

2. Non-Septate Hyphae

Definition:

Those hyphae, which lack septa & are not divided into individual cells, instead

these are in the form of long, multinucleated large cells are called Non-septate

or Coenocytic Hyphae.

Example Mucor & Rhizopus

Cell Wall of Hyphae

Chitin is the chief component present in the cell wall of most fungi, Because, it

is more resistant to decay than are the Cellulose & lignin which make up plant

cell wall.

Cytoplasm of Hyphae

In septate Hyphae –Cytoplasm flows through the pores of septa from cell to

cell, carrying the materials to growing tips & enabling the hyphae to grow

rapidly, under favorable conditions. In non-septate hyphae – cytoplasm moves

effectively, distributing the materials throughout.

Nuclei of Hyphae

All fungal nuclei are Haploid except for transient diploid zygote that forms

during sexual reproduction.



Main Function of Hyphae

Extensive spreading system of Hyphae provides enormous surface area for

absorption.

Nutrition in Fungi

Absorptive Heterotrophs

All fungi lack chlorophyll & are heterotrophs (obtain carbon & energy from

organic matter, they obtain their food by direct absorption from immediate

environment & are thus “Absorptive Heterotrophs”.

Different Modes of Heterotrophic Nutrition in Fungi

Being Heterotrophic, fungi can exist as;

1- Saprotrophs or saprobes (Decomposers)

2- Parasites

3- Predators

4- Mutualists

1. Saprobic or Saprotrophic Fungi (Decomposers)

Saprobic fungi along with bacteria, are the major decomposers of biosphere,

contributing to the recycling of the elements (C,N,P,O,H & etc) used by living

things.

Definition:

“Those fungi which obtain their food (energy, carbon & nitrogen), directly by

digesting the dead organic matter are called “Saprobic Fungi” OR

“Decomposers”

Mechanism of Absorbing Food (Development of Rhizoids)

These fungi anchor to the substrate by modified hyphae, the RHIZOID, which

provide enormous surface area for absorptive mode of nutrition.

Secretion of Digestive Juices

Saprobic fungi secrete digestive juices, which digest organic matter & the

organic molecules thus produced are absorbed, back into the fungus.

2. Parasitic Fungi

Definition:



Those fungi which absorb nutrients directly from living host cytoplasm are

called Parasitic Fungi.

Mechanism

For obtaining, their food requirements, these fungi develop specialized hyphal

tips called as Haustoria which penetrate the host tissues for absorbing nutrients.

Types or Parasitic Fungi

Parasitic fungi may be of two types

A. Obligate Parasites

B. Facultative Parasites.

(A) Obligate Parasites

Definition:

Those parasitic fungi which can grow only in their living host & cannot be

grown on available defined growth culture medium, are called “Obligate

Parasites”.

Examples

• Many mildews

• Most of Rust species.

(B) Facultative Parasites

Definition:

“Those parasitic fungi which can grow parasitically on their host as well as by

themselves on artificial growth media, are called “Facultative Parasites”.

3. Predatory Fungi

Definition:

“Those fungi which obtain their food by killing other living organisms are

called Predatory Fungus.

Examples

1. Oyster Mushrooms (Pleurotus astreatus ).

2. Some species of Arthrobotrys.

Mechanism of Obtaining Food

1. In Oyster Mushrooms

Oyster mushroom is a carnivorous fungus. It Paralyses the nematodes (that feed

on this fungus), penetrate them & absorb their nutritional contents, primarily to

fulfill nitrogen requirements. It fulfills it glucose requirements by breaking the

woods.



2. In Arthrobotrys

• Constrictor ring development

Some species of Arthrobotrys trap soil nemotodes by forming Constricting

Ring, their hyphae invading & digesting the unlucky victim.

4. Mutualistic Fungi

Definition:

“Those fungi which form such symbiotic associations with other living

organisms in which both partners of association get benefit from each other are

called Mutualistic Fungi & Such association are called as “Mutualistic

Symbiotic Associations”.

Two Mutualistic Symbiotic Associations Formed By Fungi

Fungi form two key mutualistic symbiotic associations. These are:

1. Lichens

2.Mycorrhizae

1. Lichens

Symbiotic Partners in Lichens

Lichens are mutualistc & have symbiotic associations b/w certain fungi (mostly

Ascomycetes) & imperfect fungi & few Basidiomycetes (about 20 out of 15000

species of lichens) & certain photoautotroph either green algae or

cynobacterium or sometimes both.

Mutual Benefit

In lichens, fungi protect the algal partner from strong light & desiccation &

itself gets food through the courtesy of alga.

Areas Where Lichens Grow

Lichens can grow at such places such as bare rocks & etc, where neither of the

components alone can grow.

Ecological Importance of Lichens

From ecological point of view, lichens are very important because they serve as

Bio Indicators of Air Pollution.

2. Mycorrhizae

Symbiotic Partners

Mycorrhizae are mutualistic association b/w certain fungi & roots of vascular

plants (about 95% of all kinds of vascular plants).



Mutual Benefit

The fungal hyphae dramatically increase the amount of soil contact & total

surface area for absorption & help in direct absorption of nutrients from soil.

The plant on the other hand, supplies organic carbon to fungal hyphae.

Types of Mycorrhizae

There are two main types of mycorrhizae.

1. Endomycorrhizae

2. Ectomycorrhizae

1. Endomycorrhizae

In Endomycorrhizae, the fungal hyphae penetrate the outer cells of plant root,

forming coils, swellings & minute branches, & also extend out into surrounding

soil.

2.Ectomycorrhizae

In Ectomycorshizae the hyphae surround & extend between the cell but don’t

penetrate the cell walls of roots.

Example

Mutualistic association between fungi & pines & firs

Reproduction in Fungi

Two kinds of reproduction are usually found in Fungi

1. Asexual Reproduction

2. Sexual Reproduction

Except In perfect, Fungi in which sexual reproduction has not been observed.

1. Asexual Reproduction

Definition:

The most common means of reproduction in fungi which does not involve

sexes, reduction division & fertilization is called A Sexual Reproduction

Different Modes Of Asexual Reproduction.

In fungi, asexual reproduction take place by following ways:

1- Spore Formation

2- Conidia Formation

3- Fragmentation

4- Budding.



1- Spore Formation

Introduction

It is the most common type of asexual reproduction in fungi in which large no

of spores are developed with in the sporangia. Each spore on generation

produces another mycelium.

Explanation of the Process

Spores

Spores may be produced by sexual or asexual process, are haploid, thick walled,

non-motile & not needing water for their dispersal, they are very small &

produced in very large no. within the Sporangium.

Sporangium

Spores are produced inside the reproductive structures called Sporangia, which

develop as swellings at the tips of Sporangiophores.

Separation of Sporangium from Hyphae

After the formation of spores, sporangium becomes separated from hypae by

some complete septa.

Breakage of Sporangial Wall

On maturity of the spores, the outer wall of sporangium breaks down & spores

are dispersed.

Dispersion of Spores

Spores are usually dispersed by air currents to great distances & cause wide

distribution of many kinds of fungi. They may also be dispersed by small

animals & insects & by rain splashes.

Germination of Spores

In a favorable condition, on a proper substrate, the spore germinates giving rise

to new fungal hyphae.

2.Conidia Formation

Introduction

The type of asexual reproduction in fungi in which large number of asexual

spores called “Conidia are formed, each on germination giving rise to new

mycelium is known as Conidial Reproduction.

Explanation

Conidia



Conidia are non-motile, asexual spores which may be produced in very large

number & can survive for weeks, causing rapid colonization on new food.

Conidiophores

Conidia are not developed inside the sporangium but they are usually cut off at

the end of modified hyphae called Conidiophores, commonly in chains or

clusters.

Example

Asexual reproduction by conidia formation is very common in Ascomycetes.

3.Fragmentation

It is the type of asexual reproduction in which mycelium of some fungal hyphae

breaks into pieces or fragments. Each fragment develops into a new mycelium.

4. Budding

Introduction

Budding is an asymmetric asexual division in which tiny outgrowth or bud is

produced which may separate & grow by simple relatively equal cell division

into new mycelium.

Example: Unicellular yeasts reproduce by budding

Sexual Reproduction

Introduction

Details of sexual reproduction very in different groups of fungi on the basis of

which fungi can be divided into four major phyla, However the fusion of

haploid nuclei & meiosis are common to all.

Explanation

Sexual reproduction in fungi takes place through several stages, which are as

follows.

Plasmogamy

When fungi reproduce sexually, hyphae of two genetically different but

compatible mating types come together & their cytoplasm fuse. This process is

called Plasmogamy, this step is common in all types of fungi.

In Zygomycota after Plasmogamy following steps occur.

Karyogamy



In zygomycetes, Plasmogamy is followed by fusion of nuclei, called as

Karyogamy.

Zygot Fomation & Meiosis

In Zygomycetes, fusion of nuclei, leads directly to the formation of zygot,

which divides by meiosis when it germinates.

In Ascomycota and Basidiomycota

In these groups of fungi, following steps after plasmogamy.

Formation of Dikaryotic Nyphae

In these groups, the two genetic types of haploid nuclei from two individuals by

coexist & divide in the same hyphae for most of the life of fungus. Such as

fungal hyphae are called Dikaryotic Or Heterokaryotic Hypha/Cell.

Formation of Fruiting Bodies

Extensive growth of dikaryotic hyphae may lead to the formation of massive

structures of interwoven hyphae called as Fruiting Bodies, such as

• Basidia/ Basidiocarps

• Asci/ Ascocarps

Syngamy & Meiosis

Fusion of two haploid nuclei occurs within the fruiting bodies forming a zygote,

this is called as Syngamy, followed immediately by meiosis.

Formation of Haploid Sexual Spores

Each zygote divides immediately by meiosis to form four haploid spores, which

when release is dispersed, some of them giving rise to new hyphae.

Classification of Fungi

There are four major divisions of fungi, which are divided on the basis of their

sexual reproduction.

1- Zygomycota

2- Ascomycota

3- Basidiomycota

4- Deuteromycota

1- Zygomycota

Introduction



Zygomycota are by far the smallest of four groups of fungi, with only about 600

named species. This group includes more frequently bread molds as well as a

variety of other microscopic fungi found on decaying organic material.

Characteristic Feature

The group is named after a characteristic feature of the life cycle of its member,

the production of temporalily dormant structures called Zygospores.

The zygomycetes lack septa in their hyphae i.e coenocytic hyphae, except when

they form sporangia or gametangia.

Life Cycle of Zygomycota

In the life cycle of zygomycota, two types of reproduction occur:

A- Sexual Reproduction in Zygomycota

B- Asexual Reproduction in Zygomycota

(A) Sexual Reproduction in Zygomycota

Sexual reproduction takes place by fusion of Gametangia in following steps:

Formation of Progametangium

When two hyphae came in contact with each other, each of them gives a lateral

progametangium, facing each other.

Differentiation Of Progametangia Into Gametangia & Suspensors

Later on, each of the progametangium differentiates into two parts

• Apical swollen part called Gametangium, containing numerous nuclei

• Basal hollow part called Suspensor.

Gametangial Copulation

The gametangia may be formed on hyphae of different mating types or on some

single hyphae. If different mating types are involved, fusion between pairs of

haploid nuclei occurs immediately.

Zygot Formation

Fusion of haploid nuclei results in formation of diploid zygote nuclei, Except

for the zygote nuclei, all nuclei of zygomycota are haploid.

Zygospore Formation

After the formation of diploid zygote nuclei, the fused portion of hyphae

develops into Zygospores.



Germination of Zygospore

Under favorable condition zygospore germinates & giving rise to new

mycelium. Meiosis occurs during germination.

(B) Asexual Reproduction in Zygomycota (By Spore Formation)

Asexual reproduction occurs much more frequently than sexual reproduction in

the zygomycetes.

Explanation

As previously discussed in spore formation

Examples of Zygomycetes

1- Mucor

2- Rhizopus Stoloniper

2-Ascomycota

Introduction

The second division of fungi, the Ascomycota is a very large group of about

30,000 named species with many more being discovered each year.


The ascomycota are named for their characteristic reproductive structure, the

microscopic, club shaped Ascus.

Type of Hyphae

The hyphae of ascomycetes are divided by septa i.e septate hyphae, but the

septa are perforated & the cytoplasm flows along the length of each hyphae.

The septa that cut off the asci & conidia are initially perforated like all other

septa, but later they often become blocked.

Life Cycle of Ascomycota

In life cycle of ascomycota, both sexual & asexual reproduction occurs.

(A) Sexual Reproduction in Ascomycota:

Sexual reproduction occurs through following steps.

1-Formation of Male Gametangium or Antheridium

The hyphae of ascomycetes may be either homokaryotic & heterokaryotic. The

cells of these hyphae usually contain from several to many nuclei. These cells

form Antheridium or male gametangium.

2-Female Gametangium or Ascogonium



The gametangium which develop beak like out growth called as Trichogyne, is

called female gametangium or Ascogonium.

3-Fusion of Male & Female Gametangium

When antheridium is formed, it fuses with trichogyne of an adjacent

ascogonium. Fusion of cytoplasm or plasmogamy occurs.

4-Pairing of Nuclei

After plasmogamy, nuclei from antheridium then migrate through the

trichogyne into the ascogonium, & pair with nuclei of opposite mating types.

5-Formation of Dikaryotic Hyphae & Dikaryoticy

Dikarytic hyphae then arise from the area of fusion. Throughout such hyphae,

nuclei that represent the two different original mating types occur (Dikaryoticy)

Such hyphae are also called as Heterokaryotic Hyphae.

6-Formation of Ascocarps or Fruiting Bodies

Excessive growth of monokaryotic or dikaryotic hyphae results in formation of

massive structures of tightly interwoven hyphae, called as Fruiting Bodies Of

Ascocarps, which corresponds to the visible portions of a morel or cup fungus.

7- Asci Formation

Asci are special reproductive structures which are formed on special fertile

layers of dikaryotic hyphae with in the Ascocarps.

8- Separation of Asci

-+The asci are cut off by the formation of septa at the tips of heterokaryotic

hyphae.

9- Syngamy

There are two haploid nuclei with in each ascus one of each of which belongs to

different mating type. Fusion of these two nuclei occurs within each ascus

called as Syngamy.

10-Zygot Formation

Syngamy results in zygote formation, which divides immediately by meiosis,

forming four haploid daughter cells.

11- Formation of Ascospores

Four haploid daughter nuclei, usually divide again by mitosis, producing 8

haploid nuclei that become walled & called Ascospores.



12-Bursting of Ascus

In most Ascomycetes, the ascus becomes highly turgid at maturity and

ultimately bursts, often at a perforated area, which may be pore or slit or lid

13- Despersion & Germination of Ascospores

After bursting, the ascospores may be thrown as far as 30 cm. Under favorable

circumstances they germinate giving new hyphae.

Types of Ascocarps in Ascomycetes

According to their shape, Ascocarps are of following three types:

1- Opothecium

The ascocarps of cup fungi & the morels are open, with the asci lining the open

cups called Opothecium.

2- Cleistothecium

Some ascocarps are closed & called as ‘Clestothecium’.

3- Perithecium

Some ascocarps have small opening at the apex called as Perithecium.

Ascocarps of Neurospora are of this type.

(B) Asexual Reproduction in Ascomycota (By Condia Formation):

Introduction

The type of asexual reproduction in fungi in which large number of asexual

spores called “Conidia” are formed, each on germination giving rise to new

mycelium is known as Conidial Reproduction.

Explanation

Conidia

Conidia are non-motile, asexual spores which may be produced in very large

number & can survive for weeks, causing rapid colonization on new food.

Conidiophores

Conidia are not developed inside the sporangium but they are usually cut off at

the end of modified hyphae called Conidiophores, commonly in chains or

clusters.

Example

Asexual reproduction by conidia formation is very common in Ascomycetes.



3.Basidiomycota

Introduction

The basidiomycetes, third division of fungi have about 16,000 named species.

More is known about some members of this group than about any other fungi.


Basidiomycetes are named for their characteristic sexual reproductive

structures, the Basidium, which is club shaped like as ascus.

Life Cycle of Basidiomycota

In life cycle of Basidiomycota, reproduction is usually sexual. Asexual

reproduction is not very important.

(A) Sexual Reproduction in Basidiomycota

The life cycle of basidiomycetes begins with the production of hyphae which

may be of two types.

1- Homokaryotic hyphae giving rise to primary mycelium.

2- Heterokaryotic hyphae giving rise to secondary mycelium.

Primary or Monokaryotic Mycelium

Homokaryotic or monokaryotic hyphae lack septa at first. Eventually, However,

septa are formed between nuclei of these hyphae. A basidiomycete mycelium

made up of monokaryotic hyphae is called Primary Mycelium.

Secondary or Dikaryotic Mycelium

Mycelium of basidiomycetes, with two nuclei, representing the two different

mating types b/w each pair of septa, is called Secondary or Dikaryotic

Mycelium. Most of the mycelium of basidiomycetes that occur in nature is

dikaryotic & often only dikaryotic mycelium is able to form basidiocarps.

Formation of Basidiocarp Or Fruiting Body

Dikaryotic mycelium is responsible for the formation of Fruiting Body in

Basidiomycetes called as Basidiocarp, made up of tightly interwoven dikaryotic

hyphae.

Formation of Basidium

Basidium is characteristic reproductive structure of Basidiomycetes, which is

club shaped & formed with in the Basidiocarp. This produces slender projection

at the end called as Sterigmata, in this way.

Syngamy & Zygot Formation



Nuclear fusion or syangamy occurs in Basidium, giving rise to diploid zygote,

the only diploid cell of the life cycle.

Meiosis & Basidiospore Formation

Meiosis occurs immediately after the formation of zygot, resulting in the

formation of four haploid nuclei, which are incorporated in Basidiospores. In

most member of this division basidiospores are borne at the sterignata

Dispersion and Germination

Same as in Ascomycetes.

(B) Asexual Reproduction in Basidiomycota

In contrast to their effective sexual reproduction, asexual reproduction is rare in

most basidiomycetes.

Examples of Basidiomycetes

• Mushrooms

• Toad Stools

• Puff Balls

• Jelly Fungi

• Shelf Fungi

• Plant Pathogens Called Rusts & Smuts,

4.Deuteromycota (Fugi Imperfecti)

Introduction

“The fungi that are classified is this group, are simply those in which the sexual

reproductive stages have not been observed. In other words, most of the Fungi

Imperfecti are as ascomycota that have lost the ability to reproduce sexually.

There are some 17000-described species of this group.”


Sexual reproduction is absent among Fungi Imperfecti

Life Cycle of Deuteromycota

Although in life cycle of deuteromycetes or Fungi Imperfecti, true sexual

reproduction is absent, but there is certain type of Genetic Recombination which

seems to be responsible for some of the production of new pathogenic strains of

wheat rust.

Genetic Recombination in Fungi Imperfecti Parasexuality



In Para sexuality, exchange of portions of chromosomes between the genetically

distinct nuclei with in some common hyphae takes place. This is the special

type of genetic recombination occurs in fungi Imperfecti.

Examples of Fungi Imperfecti

Among the economically important genera of Fungi Imperfecti are

1-Penicillium

2- Aspergillus

3- Most of the fungi that cause skin diseases in humans, including athlete’s foot

& ring worm are also fungi imperfecti.

Economic Importance of Fungi

Fungi play a vast role in economic field they show both harmful & useful

activities to human beings.

Useful Fungi

Following are some of the beneficial effects of fungi.

Food

Many kinds of edible fungi are in the form of mushrooms, are a source of

nourishing & delicious food dishes. But not all the mushrooms are edible. Some

of them are poisonous & called as toad stools or death stool. Yeast, another kind

of fungi, are utilized in baking industry.

Medicines

Nearly two dozen antibiotics have been isolated from different types of fungi &

bacteria, like

• Penicilliun from penecillium notatum

• Neomycin

• Chloromycetin

• Tetramycin & etc.

Food Production

Many kinds of Yeast are used in the production of bakery & brewery products.

Some species of genus Penicillium give characteristic flavors & aromas to the

cheese.

Fermentation

Species of Aspergillus, are used for fermenting soya sauce & soya paste. Citric

Acid is produced commercially with members of this genus under highly acidic

condition.



Soil Fertility

Fungi maintain the soil fertility by decomposing the dead organic matter e.g

Mycorhizal fungi.

Production of Organic Compounds

May species of fungi are used in the production of organic compound such as

vitamins, proteins & fats. Saccharomyces, synthesizes a range of vitamin B

group.

Harmful Fungi

Following are some of the harmful effects of fungi,

Food Spoilage

Saprophytic fungi cause tremendous amounts of spoilage of food stuff. 15-20%

of worlds fruit is lost each year due to fungal attack.

Spoilage of Wood & Leather Articles

Many fungi spoil leather goods, woods, wool, books, timber, cotton & etc.

Wood-Rotting Fungi destroy not only living trees but also structural timber.

Bracket/Shelf Fungi cause lot of damage to store cut lumber as well as stands of

timber of living trees.

Toxins

Many fungi are poisonous. Amanita Verna is a mushroom, which produces

deadly poisonous substance known as Amanitin, which causes serious problems

in respiratory system & blood circulatory system.

Food Poisoning

Some fungi during decomposing food release certain poisonous substances

collectively known as Mycotoxins. Mycotoxins are the major source of food

poisoning.

Diseases

Fungi cause a number of diseases in plants as well as in human beings.

Plant Diseases Caused by Fungi

Fungi destroy many agricultural crops, fruits, ornamentals & other kinds of

plants because they produce several enzymes that can breakdown cellulose,

Lignin and even cutin. Following are some of the serious plant disease caused

by Fungi.

Rust & Smut Diseases



Rust & smut diseases are serious diseases of Wheat, Rice, Corn &other cerial

crops. They cause extensive damage.

Potato Blight

A serious disease of potato caused by a fungus known as Phytopthora Infestans.

Other plant disease is.

• Powdery mildews (on grapes, rose, wheat & etc).

• Ergot of rye

• Red rot of sugar cane

• Potato will

• Cotton root rot

• Apple scab

• Brown rot of peaches, plums, apricots & cherries.

Animal Diseases Caused by Fungi

Following are some of the fungal diseases in man.

Skin Diseases

Ring Worm & Athelete’s Foot are superficial fungal infection caused by certain

Fungi Imperfection.

Oral Thrush

Canidia Albicans, a yeast causes oral & Vaginal thrush.

Aspergillosis

Aspergillosis is the disease of ear & lungs caused by Aspergillus. It occurs only

in person with defective immune system such as AIDS & cause death.

Cancer

Some strains of Aspergillus Flavus produce one of the most carcinogenic

(cancer causing) mycotoxins called Aflatoxins.

Ergotism

Ergotism is caused by eating bread made from Purole Ergot- Contaminated

flour. The poisonous material in the ergot causes nervous spasm, convulsions,

psychotic delusion & even gangrene.

Histoplasmosis

Histoplasmosis is a serious disease of lungs caused by inhaling spores of a

fungus, which is common in soil contaminated with bird’s feces.



CHAPTER 9

THE KINGDOM PLANTAE

Introduction

• Includes all eukaryotic multicellular and chlorophyllous living organisms,

which have cell wall made up of true cellulose.

• Majority of members are autotrophic but few are parasite e.g.: “Cuscuta”



• They have localized growth, regions of growth lying primarily at the

extremities that is root and stem apices.

Classification Of Kingdom Plantae

Kingdom planatae is divided into two sub-kingdoms on the basis of presence or

absence of vascular tissue (xylem and phloem).

A - Sub-Division - Bryophytes (Non-Vascular)

• Class Hepatica (Liverworts)

• Class Musci (Mosses)

• Class Anthroccrota (Hornworts)

B- Sub-Division - Tracheophytes

• Class Psilopsida (Psilopsids)

• Class Lycopsida (Club Mosses)

• Class Sphenopsida (Horse Tails)

• Class Pteropsida (Ferns)

• Class Spermopsida (Seed Plants)

Sub –Division Bryophyta (Amphibian Plants) Or (Non-Vascular Plants)

• Absence of lignin-fortified tissue to support tall plants on land.

• Members of this sub-division usually sprawl horizontally as mats over a

large surface.

• Always have a low profile (1-2cm-20cm tall).

Regular heteromorphic alternation of generation is present w/t gametophytes

dominancy (Gametophytes large and long lived).

• Sporophyte stage of bryophytes is generally smaller and shorter lived, and it

depends on gametophyte for water and nutrients.



• The diploid sporophyte produces haploid spores via meiosis in a structure

called “sporangium”

• The tiny, spores, protected by sporopollenim, disperse and give rise to new

gametophytes.

• All members of bryophytes need water to reproduce.

• Gametes produce within reproductive structures “Gametangia” (Male-

Antheridia and Female-Archer-gonium)

• Antheridium produces flagellated sperm while female archegonium contains

one egg (ovum).

• Fertilization occurs w/t in the archegonium.

• Zygote develops into an embryo within the protective jacket of

Archegonium.

• Windblown spores disperse the speies.

• All bryophytes belong to Silurian/Devonian period (345-395Million yrs.

Ago.)

Adaptation Of Bryophytes To Land Habitat

All Bryophytes show amphibious form of land plants. Following are main

adaptations exhibited by them.

a. Rhizoid for water absorption

b. Conservation of water

c. Absorption of CO2

d. Heterogamy

e. Protection of reproductive cells

f. Formation of embryos

Classes Of Bryophytes

1-Musci (Mosses)

• Plants grow in a tight pack, in the form of mat, in order to hold one another

up.



• Mat of moss possess spongy quality and enables it to absorb and retain

water.

• Rhizoids are elongated cells or cellular filaments of mats which grip the

substratum.

• Photosynthesis occurs in upper part of the plant w/c has many small stem

like and leaf like appendages. E.g Funaria.

2-Hepaticae (Liverworts)

• Usually present in tropical areas

• Plant body is divided into lobes somewhat of the lobed liver, of an animal.

• These plants are less fimiliar than Mosses.

E.g Marchantia

3- Anthroceratae: (Hornworts)

• These plants resemble w/t liverworts, but are differentiated by their

sporophytes plants.

• Sporophyte are elongated capsules that grow like horn from mat like

gametophyte.

• Sporophyte has stomata and chloroplast, performs photosynthesis

• Sporophyte plant can survive even often the death of gametophyte due to

presence of Meristem.

• Meristem is a specialized tissue, which keeps on adding new cells in

sporophyte plant.

• Hornworts are the most advanced members of bryophytes.

• E.g Arthroceros

Sub-Division Tracheophyta (Vascular Plants)

Main characters are as follow;



• Conducting vessels Xylem and Phloem are present in plant body.

• A protective layer of sterile “Jacket” cells around reproductive organs are

present.

• Multicellular embryos retained within the archegonia.

• On aerial parts, protective covering “Cuticles” is present w/c prevents

excessive loss of water during hot climate.

• In life cycle Sporophyte stage is dominant.

Classes Of Tracheophytes

1-Psilopsida

• These are the fossil representatives of the vascular plants, belonging to

“Silurain period” and “Devonian Period”

• Sporophytes are simple dichotomously branching plants.

• True leaves and true roots absent.

• Underground stems that contain unicellular rhizoid similar to root hairs.

• The aerial stems are green and carry out photosynthesis.

• Lacking secondary growth due to absence of “Cambium”

• Reproductive structure “Sporangia” develop at the tips of some of the aerial

branches.

• Meiosis produces haploid spores, within the sporangia.

• E.g. Rhynia, Psilotum Temesipteris

A) Rhynia (First Vascular Plant)

• One of the most primitive vascular plant

• It is an extinct genus, was named often the village “Rhynia of Scotland

where the first fossils of Rhynia were discovered.



• It belongs to Devonian period, which started about 400 million years ago.

• The fossils of this plant are so well preserved that the stomata are still intact.

Structure

• The plant body (Sporophyte) was simple.

• It consisted of slender, dichotomously branched creeping rhizome, bearing

erect, dichotomously branched aerial stem.

• Instead of roots, rhizoids were given out from rhizome.

• The aerial branches were leaf-less having terminal fusiform naked sporangia.

Microscopic Structure

• The internal structure of branches show a solid central core of vascular

tissues surrounded by Cortex.

• The outer most layer is Epidermis having stomata.

• The vascular tissue is differentiated into centrally placed xylem and

surrounded phloem.

B) Psilotum And Temesipteris (Living Species of Psilopsida)

• Sporophyte plant produce spores, which give rise to minute subterranean

gametophytes.

• Each gametophyte bears both female reproductive organ Archegonia and

male reproductive organ Antheridia w/c produce both egg and sperm

respectively.

• As a result of fertilization, a diploid zygote is formed which develops into

sporophyte plant.

• Sporophyte stage of life cycle is dominant, but haploid gametoplyte stage is

still relatively large.

Evolution Of Leaf



The leaf is the most important organ of a green plant because of its

photosynthetic activity. Leaves are of two types;

1. Single veined leaves- Contain only one vein

2. Poly veined leaves- Contain two or more veins

1- Evolution Of Single-Veined Leaf

• It is assuming that a thorn like out growth emerged on the surface of the

naked stem.

• With an increase in size of the leaf, the vascular tissues were also formed for

the supply of water and support to the leaf.

• Another possibility is that a single veined leaf originated by a reduction in

size of a part of the leafless branching system of the primitive vascular

plants.

2. Evolution Of Poly-Veined Leaf

• These are the evolutionary modifications of the forked branching in the

primitive plants.

• The first step in the evolution of this leaf was the restriction of forked

branches to a single plane.

• The branching system become flat.

• The next step in the evolution was filling the space b/w the branching and

the vascular tissues.

• The leaf so formed looked like the webfoot of a duck.

2-Lycopsida(The Club Mosses)

• These plants belong to middle Devonian and carboniferous periods.

• They were very large trees that formed the earth’s first forests.

• Only five living genera of this group are present.

• Two members, selaginella and lycopodium are common in many areas of

Pakistan



• These plants have true branched underground roots.

• True leaves also present w/c have arisen as simple scale like outgrowth

(emergence) from the outer tissues of the stem.

• Specialized reproductive leaves bearing sporangia on their surfaces, are

present, such type of leaves are known as “Sporophylls”.

• In some members, the sporophylls are collected on a short length of stem and

form cone like structure “Strobilus”.

• The cone is rather club-shaped; hence name “Club-Mosses” for the

lycopsids.

• Gametophytes plant may be homosporous or heterosporous .

A) Homosporous Gametophytes

Spores produced by sporophyte plant are all alike, and each give rise to some

gametophytes that bear both archegonia (female reproductive structure) and

antheridia (male reproductive structure)

Example Lycopodium (Running pine or ground pine)

B) Heterosporous Gametophytes

• Sporophyte (2n) plant produces two types of sporangia, which produced

different kinds of spores.

• One type of sporangium produces very large spores called “Megaspores,”

which develop in female gametophytes bearing archegonia.

• Other type of sporangium produces small spores called “Microspores, which

develop into male gametophytes bearing antheridia.

• That’s mean sexes are separate in the gametophytes generation

(Heterosporous).

• Example: Selaginella.

Evolution Of Seed

Seeds are evolved from primitive spores.



Steps of Evolution

1. Primitive Spores

All spores of specie are nearly identical in size, structure and function.

2. Heterospores

• There are many vascular plants that form two kinds of spores, these plants

are said to be “Heterosporous” and spores are called “Heterospores.”

• These spores on germination give rise to two different types of plants.

A) Male Spore: It produces sperm forming gametophyte plant.

B) Female Spore: It grows into egg forming gametophyte.

3. Protection Of Heterospores

• The two different kinds of spores are formed in two different kinds of

sporangia.

• Various enveloping structures develop in order to protect these spores.

• Certain fern like plants first developed seed like structures, each of their

sporangia, containing one or more female spores, was surrounded by little

branch like out growth structure forming “Integument.”

4. Persistance of Female Spores

• Instead of being shed from the sporangium, the female spores are retained

and protected inside the integument.

• The female spore develops into a tiny female gametophyte protected by the

integuments.

5. Formation and Structure of Seed

• Seed is formed as the result of fertilization of male spore with this protected

female spore.

• Immature seed is called “Ovule.”



• Ovule is protected by integuments and it contains great quantities of food.

• Ovule not only protects the female gametophyte from the environment but

also provides food for the new off springs that is produced when the seed

matures and germinate. The development of seed has given the vascular

plants better adaptations to their environment.

3. Sphenopsida (The Horse Tails)

• These plants belong to late Devonian and Carboniferous period.

• Only one living member “Equisetum” commonly called “Horse-tail” exists

today.

• Ancient sphenopsids were large trees but now most of these are small (Less

than one meter).

• Coal deposits of today was formed from the dead bodies of those plants.

• These plants possess true roots, stems and leaves.

• Stems are hollow and are jointed, whorls of leaves occur at each joint.

• Secondary growth absent, because modern species do not possess cambium.

• Spore are born in terminal cones (Strobili) and all are alike (i.e. plants are

homosporous) and give rise to small gametophytes that bear both archegonia

and antheridia (i.e. the sexes are not separate).

4. Pteropsida (The Ferns)

• These plants belong to Devonian and Carboneferous Period and then decline

in Paleozoid Period.

• They are very well developed plants having vascular system with true roots,

stem and leaves.

• Leaves are probably arisen from flattened web branched stems. They are

large and provide much greater surface area for photosynthesis.



• Leaves of Ferns are sometimes simple, but more often they are compound,

being divided into numerous leaflets.

• In most modern ferns of temperate regions, the stems are prostrate on or in

the soil, and the large leaves are only part normally seen.

Sporophytic Stage

• The large leafy plant (fern) is diploid sporophytic phase.

• Spores are produced in sporangia (Reproductive structure) located in clusters

on the underside of some modified leaves “Sporophyll.”

• Most modern ferns are homosporous i.e. all these spores are alike.

• Vascular sporophytes can live in drier places and grow bigger.

Gametophyte Stage

• After germination, the spores develop into gametophytes that bear both

archegonia and antheridia.

• These gametophytes are tiny (less than one centimeter wide), thin and often

more or less heart-shaped.

• Free-living, non-vascularized gametophytes can survive only in moist places,

their sperms are flagellated and water is required for fertilization. Young

sporophyte develops directly from the zygote without passing through any

protected seed like stage.

Alternation Of Generation

• In Kingdom Plantae, life cycle of many plants is completed in two stages or

generations known as Gametophyte and Sporophyte.

• The two generations normally differ from each other in morphology,

reproduction and number of chromosomes.

• The gametophyte is haploid and reproduces sexually by forming the

gametes, while the sporophyte is diploid and reproduces a-sexually by

forming the spores.

• The two generations regularly alternate with each other and therefore, the

phenomenon is called “Alternation of generation” (Heteromorphic).



• In Bryophytes, the main plant itself is the Gametophyte while the sporophyte

is reduced.

• In Tracheophytes, the main plant is “Sporophyte” and the “Gametophyte” is

reduced.

5. Spermosida (The Seed Plants)

• First appeared in late Devonian and became dominant in Carboniferous

Period.

• Gametophyte stage is even more reduced than in the ferns, and non-

photosynthetic or free-living.

• The sperms of most modern species are not independent free-swimming

flagellated cells.

• Young embryo, is enclosed within a seed coat and can remain dormant for

long periods.

• Spermosida can be divided into two main sub-groups, which are as follows:

i) Gymnosperms

ii) Angiosperms

I) Gymnosperm

• These plants have naked seed because ovules are not covered by ovary i.e.

fruit is absent.

• Sub-divisions of Gymnosperms are;

a) Cycads

b) Gnetae

c) Ginkgo

d) Conifers

A) Cycads'

• They have arisen from the seed ferns.



• These plants appeared in “Permian Period” and Mesozoic Period and

declined in Cretaceous Period.

• They possessed large palm like leaves with short height stems.

• Living species commonly found in tropical regions and also known as “Sago

Palms.”

• Nine living genera with over a hundred species exist today.

• Cycads and its relatives.

B) Ginkgoae'

• Mostly contains extinct species, only one living specie, “the Ginkgo” which

is also known as “Maiden Hair Tree.”

• Ginkgo often planted as lawn tree.

• E.g: Ginkgo Biloba.

C) Conifers

• Most familiar and best-known group of gymnosperms.

• Leaves are small evergreen needles or scales with an internal arrangement of

tissues.

• Reproductive organs are cone like modified leaves.

• E.g: Pinus.

Pinus

This plant belongs to Gymnosperms. It includes about 90 species.

Habit and Habitat

• It is distributed world-wide mostly in northern hemisphere. 30 species are

found in the Himalayas. Some are reported in the planes of Punjab.

Morphology



• The pinus plant belongs to the “Sporophytic Phase.”

• It is a tall tree, pyramidal in form and gives a conical appearance and

therefore commonly grouped under “Conifers.”

• It is well differentiated into stem, root and leaves.

Stem

It is erect, cylindrical, solid and covered with thick, rough and brownish bark.

The branches are dimorphic,

• Branches of unlimited growth or long shoot.

• Branches of limited growth or dwarf shoot.

Roots

Underground root system is formed by “Tap Roots” which disappear early and

only lateral roots persist later on.

Leaves

It bears two types of leaves (dimorphic condition)

a) Scale leaves

b) Foliage leaves

A) Scale Leaves

• Thin, membranous small scale like structures.

• Provide protection and do not help in photosynthesis.

B) Foliage Leaves

• Only develop on dwarf shoots.

• Number of foliage leaves is fixed for particular specie.

• Each leave is needle shaped, simple green therefore also known as

“Needles.”



• They have smooth surface and are evergreen and persistent.

Life Cycle Of Pinus

• The adult plant of Pinus represents the “Sporophytic Phase” of life cycle.

• The sporophytic plant body of pinus reproduces asexually by means of

spores and after passing through “Gametophytic Phase” of the life cycle

again produce Sporophytic plant, showing distinct Alternation of Generation.

1. Sporophytic Phase

• The sporophytic plants of Pinus are mostly monoecious i.e. male and

female cones are found on same plant.

• Special reproductive organs called “Cones,” developed on it.

A) Male Cone Or O-Strobilus

• The male cones occur in clusters near the end of long branches at the

place of dwarf shoot. (Dwarf shoots are replaced by male cone).

• Each male cone is simple ovoid structure 3-4 cm in length.

• It has got single centrally located cone axis around which are arranged

spirally, many scaly microsporophylls (60-135).

• Each microsporophyll has an expanded triangular central part and a stalk

like base.

• Each microsporangium, which is born on the lower side bears numerous

“Pollen grain mother cells.”

• When the microsporangium matures, on its lower side a horizontal slit is

formed through which numerous Pollen grains are liberated and dispersed

by wind.

• Each pollen grain is winged structure and yellow in colour.

B) Female Cone Or O-Strobilus

• The female cones are developed laterally in the axis of scale leaves.



• The female cones are much bigger, woody, dry and hard structure.

• The young female cone is reddish green structure. Each female cone

consists of a central axis to which are attached the “Megasporophyll.”

• Each megasporophyll on its surface has two ovules.

• Each ovule is orthosporous and consists of a central mass of tissue,

surrounded by a single integument, made up of 3 layers.

• The integument bears a wide gap, the microphyle.

• Within the megasporangium, megaspore mother cells are present, which

undergoes reduction division to produce a “Megaspore.”

• Only one megaspore is functional, however the other three degenerate.

2. Gametophyte Phase

• The spores are the units of gametophytic phase of life cycle.

• In case of Pinus the spores are of two types, microspores and megaspores.

A) Male Gametophytes

• Microspore is a unit of male gametophyte.

• Each microspore or pollen grain is a unicellular body, covered with an

outer layer, “Exine,” thick and heavily culticularized, while the inner

layer, the “Intine” is very thin.

• The Exine forms the balloon shaped wings on either side, which help in

pollination.

• The microspore is at this, four celled stage (consisting of one generative

cell and two prothalial cells and a tube cell).

B) Female Gametophyte

• The Megaspore is the first cell of female gametophyte.



• The functional megaspore increases in size and forms a complete cellular

female gametophyte, also known as “Endosperm.”

• The “Archegonia” are formed towards micropylar side.

• The cells of the endosperm or Archegonia initial cell divides and forms

the central cell.

• The central cell forms the venter canal cell and a large egg cell.

Pollination

In case of Pinus, Pollination is effected by wind (Anemophyllous).

Fertilization

1. The pollen grains reach the apex of the Archegonium.

2. The pollen tube carrying the two male gametes and the tube nuclei comes in

contact with the archegonium.

3. The tip ruptures, discharging its contents into the egg.

4. One of the male gamete fuses with the egg nucleus and unites forming the

oospore or zygote.

5. The second male gamete along with the tube and tube nuclei disintegrate.

Pinus Seed

• Fertilized ovules get transformed into seeds.

• Seeds are small elongated and winged.

Germination of Seed

The seed undergoes into a condition of dormancy when the conditions are

favourable, the seed absorbs moisture and the embryo resume growth.

Structure Of Ovule

• Ovules are female part of flower, form seed after fertilization.

• Microscopic study of an ovule reveals following structural features of an

ovule.



1. Funicle

It is slender stalk of ovule through which it attaches to the placenta.

2. Hilum

It is the point of attachment of the body of the ovule to its funicle.

3. Raphe

In the inverted ovule, the funicle continues beyond the hilum alongside of the

body of the ovule forming a sort of ridge, which is called the “Raphe.”

4. Chalaza

The distal end of the raphe, which is the junction of integuments and the

nucellus is called the “Chalaza.”

5. Nucellus

It is the main body of ovule.

6. Integuments

Nucellus is surrounded by two coats called the “Integuments.”

7. Micropyle

It is the small opening at the apex of integuments.

8. Embryo-Sac

It is a large, oval cell lying embedded in the nucellus towards the micropyle

end. It is the most important part of the ovule as it bears the embryo. It is further

developed, and in the mature embryo sac following cells can be seen:

A) Egg Apparatus

• It is the group of three cells lying towards the micropyle.

• One cell of the group is the female gamete, the ovum/egg, and the other

two are called “Synergids.”

• The ovum or egg-cell on fertilization gives the embryo, synergids get

disorganized soon after fertilization.

B) Antipodal Cells

This is the group of three cells lying at the opposite end of egg apparatus. These

have no definite function.



C) Definitive Nucleus

In the middle of the embryo-sac there is a distinct nucleus known as a definitive

nucleus, which is the fused product of the two polar nuclei.

Structure Of Pollen Grain

• Pollen grains are male part of flowers, and are contained in the “Pollen-

Sac.”

• They are very small in size, usually varying from 10 to 200 μm.

• Microscopic study of a pollen grain shows following features:

1. Exine

• It is the outer coat of the pollen grain.

• It is tough, cutinized layer, which is often provided with spinous out

growths or markings of different patterns, sometimes smooth.

• It has one or more weak slits or pores called “Germopores.”

2. Intine

• It is the inner coat of the pollen grain.

• It is thin, delicate, cellulose layer lying internal to the exine.

• During fertilization in time grows to form pollen-tube.

3. Internal Structure

• Each pollen grain contains a bit of cytoplasm on a nucleus.

• During germination of pollen grain nucleus further divides to form a

“Tube Nucleus,” and a smaller one the “Generative Nucleus.”

• The generative nucleus soon divides into two male gametes.



CHAPTER 10

THE KINGDOM OF ANIMALIA

Classification of Kingdom Anamalia

• The classification or grouping of animals is called Taxonomy or

Systematics, primarily on the basis of their evolutionary relationships.

• Major phyla of kingdom Animalia are as follows

• Phylum Porifera (Sponges)



• Phylum Cnidaria (Coelenterata)

• Phylum Platyhelminthes (Flat worms)

• Phylum Aschelminthes (Nematoda/Round worm)

• Phylum Annelida (Segmented worms)

• Phylum Mollusca (Shelled Animals)

• Phylum Arthropoda (Jointed Appendages Animals)

• Phylum Echinodermata

• Phylum Hemichordata

• Phylum Chordata

• Summary of Kingdom Anamalia

Phylum Porifera (Sponges)

Word Porifera is derived from Latin Porus – Pores and Ferro – to bear. The

animals are also called “Sponges”.

Phylum Cnidaria (Coelenterata)

This phylum includes such simple animals having only two body layers. Hence

these are called DIPLOBLASTIC

Main Characters

Habit and Habitat

They are aquatic animals, mostly marine and few fresh water forms. They are

sedentary or free swimming and solitary or colonial.

Structure

• The cnidaria are metazoa having the simplest type of body wall

consisting of two layers. The outer epidermis and the inner gastrodermis

which lines the body cavity.

• In between the two layers lies the mesogloa, non-cellular jelly secreted by

them.



• Cnidarians, due to their two layers’ body wall are termed as diploblastic

animals. All other metazons possesses a third layer called mesoderm in

their body wall, laying in between the epidermis and gastrodermis

(Endoderm) and are therefore called Triploblastic animals.

• They have radially symmetrical body plan organized as a hollow sac.

• The mouth is surrounded by a circle of tentacles bearing cnidoblasts

stinging cells containing nematocysts.

• They have central digestive cavity connected to the outside by mouth.

Structural Types

The Cnidarians are radially symmetrical and occur in two types of forms.

(a) The polyp

(b) The Medusa

(A) Polyp

The polyp like Cnidarian for example sea anemone has a cylindrical body with a

mouth directed upwards and surrounded by tentacles. The basal surface of the

body is attached to the substratum.

(B) Medusa

The medusa like Cnidarians jelly fish are umbrella like in appearance. Their oral

surface, bearing the mouth is directed downwards. Whereas the aboral surface is

directed upward. The medusoid Cnidarians are usually free swimming.

Process of Feeding and Defence

• The Cnidarians feed mostly on animal diet.

• The food is digested in the gut and the waste products are expelled

through the mouth.

• The Cnidarians so named, because they possess cnidoblasts bearing

nematocysts which help in feeding and defence.

Reproduction

The Cnidarians reproduce by asexual as well as sexual methods. Polypoid

Cnidarians possess a remarkable ability to regenerate.



(A) Regeneration

If the oral part of the body is lost. The remaining part regenerates the new

mouth and the whole of tentacles.

(B) Asexual Reproduction

A sexual reproduction takes place by Budding.

(C) Sexual Reproduction

• The sexual reproduction takes place through male or female gametes

which are usually produced by different parents.

• The gametes develop in the interstitial cells and aggregate in gonads

which are located either in the epidermis or in the gastodermis.

• The fertilized egg gives rise to “Planula Larva”.

Classification Of Cnidaria (Coelenterata)

The Phylum Cnidaria is divided into three classes:

1. Hydrozoa

2. Scyphozoa

3. Anthozoa

1. Hydrozoa

As the most primitive class of the Cnidarians, Hydrozoa is thought by some

evolutionists to have given rise to both other classes. They show following

characteristic features:

• They are mainly marine, but some are fresh water species

• Many species have both polyp and medusa

For e.g: Hydra, Obelia and Physalia

2. Scyphozoa

• Most of animals of this class are commonly called “Jelly Fish”.

• They are semitransparent and are of various colours.

• Most are of marine habitat.

• For e.g: Aurelia and Cyanea (largest Jelly Fish)



3. Anthozoa

• These animals are mostly marine.

• Solitary or colonial Polyp forms are present.

• Medusa stage is absent.

• Gastrovascular cavity is divided into chambers, increase area for

digestion.

• For e.g: Sea-anemones and Corals etc

Phylum Platyhelminthes (Flat worms)

The term Platyhelminthes is derived from Greek Platy – flat and Helmenthes –

worms. This Phylum include Flat worms.

Index

* 1 Main Characters

* 2 Habit and Habitat

* 3 Nature

* 4 External Features

* 5 Internal Features

* 6 Reproduction

* 7 Examples

Main Characters

Habit and Habitat

Animals are mostly Parasitic in habitat and found in other higher animals. But

some animals are also free living.

Nature

They are triploblastic in nature i.e. body is composed of three germinal layers,

viz, ectoderm, mesoderm and endoderm.

External Features

• Their bodies are compressed dorsoventrally and shows bilateral

symmetry.

• Body shape generally worm like but vary from moderately elongated

flattened to long flat ribbons and leaf like.



• The flat worms are small to moderate in size varying from microscopic to

as long as up to 10-15 m.

• Majority of animals are white or colourless, some derive colour from

ingested food.

• Anterior end of body is differentiated into head.

• Ventral surface bearing mouth and genital pores.

• Presence of great variety of adhesive parts e.g. suckers.

• Body is covered by cuticle or by ciliated epidermis.

• Hard part consists of cuticle, spines, thorns or hooks etc.

Internal Features

• Endo and Exo skeleton are completely absent; hence the body is

generally soft.

• Acoelomate i.e. true coelom is absent.

• Body space between various organs is filled with Mesenchyme.

• Digestive system is poorly developed or absent.

• Respiratory and Circulatory systems are absent.

• Excretory system consists of Protonephridia or flame cells.

• Nervous system is primitive. The main nervous system consists of a pair

of cerebral ganglia or brain and 1-3 pairs of longitudinal nerve cords,

connected to each other by transverse commissures.

Reproduction

• Platyhelmenthes are hermaphrodite i.e. male and female sex organs are

present in same individual.

• In majority of forms eggs are devoid of Yolk but provided with special

yolk cells.

• Cross fertilization as well as self-fertilization is present.



• Life cycle may be simple or complicated involved one or more hosts.

Examples: Planaria, Liver flukes, Schistosoma and Taenia Solium etc

Phylum Aschelminthes (Nematoda/Round worm)

Nematoda are called Pin worm or round worms.

Index

* 1 Main Characters

* 2 Habit and Habitat

* 3 Nature

* 4 External Features

* 5 Internal Features

* 6 Reproduction

* 7 Examples

Main Characters

Habit and Habitat

• Nematoda have a very wide distribution and they seem to have mastered

almost every habitat.

• Free living nematodes are found in the sea, fresh water or in the soil in all

kinds of environment.

• There are also many Parasitic nematodes found in all groups of Plants and

animals.

• The Saprophagous species live in decomposing plant and animal bodies

and in rotting fruits.

Nature

They have a bilaterally symmetrical, cylindrical body, glistening smooth

surface. They are triploblastic.

External Features

• They show no trace of segmentation.

• Most of the free-living nematodes are less than a millimeter length.

• Some of the parasitic species attain a length of several meters e.g. Guinea

worm (Dracunculus medinensis).



• They are usually long, round, tapered at both ends showing very little

morphological diversity from species to species.

• The mouth of nematodes is modified for various modes of feeding such as

cutting, tearing, piercing and sucking fluids from the host.

• Body is covered by cuticle, which moults only during the period of growth.

Internal Features

• The organs are packed in parenchyma when young, but later on it

disappears in adult. So, that organs lie in a fluid filled cavity. This cavity

is termed as Pseudocoel and it has not peritoneum.

• Muscles are only longitudinal.

• Excretory system has no flame cells.

• Alimentary canal is straight with ectodermal fore and hind gut and an

endodermal mid gut.

Reproduction

• Sexes are generally separate.

• Gonades are tubular and continues with their ducts.

• Female organs are usually paired and open by vulva.

• Male organs are single and open into a cloaca.

• The life cycle of Parasitic species involves one, two or more hosts

Examples: Ascaris (Round worms), Hookworms and Thread worms etc.

Phylum Annelida (Segmented worms)

The word Annelida is derived from latin Annelus meaning little ring.

Main Characters

Nature

Annelida are triploblastic, symmetrical, coelomata and segmented metozoa.

Habit and Habitat



Annelida are mostly aquatic, marine or fresh water, burrowing or living in

tubes, some free-living forms.

External Features

• The most important feature of annelida is their metameric segmentation.

(External segmentation)

• Segmentation is indicated externally by circular constrictions or grooves

on the body wall.

• Outer covering of the body is cuticle secreted by the underlying

epidermis.

• Appendages, when present are unjointed.

• Locomotory organs are segmentally arranged, paired setae or chaetae.

Internal Features

• Body wall is contractile, consists of an outer epidermis, circular and

longitudinal muscles.

• The gut, longitudinal blood vessels and the nerve cord extend throughout

the body length, whereas other structures are repeated in each segment.

• Important character of annelida is the development of series of coelomic

compartments in their body between the gut and the body wall.

• The Coelom is a cavity, which develop within the mesoderm and is lined

by mesodermal cells.

• Segmented musculature plays an important part in locomotion of

Annelids.

Systems of Body

• Alimentary canal is tube like extending straight from mouth to anus.

• Respiration through general body surface, by gills in some forms.

• Blood vascular system is closed type.

• Blood is red due to haemoglobin.



• Excretory organs are Nephridia usually one pair in each segment.

• Nervous system consists of dorsal brain and longitudinal ventral nerve

cord.

• Sexes may be united or separate.

• Development is direct when sexes are united and indirect when sexes are

separate.

Examples: Nereis, Earthworm and Leeches etc.

Classification of Phylum Annelida

Phylum Annelida is divided into four classes:

1. Polychaeta

2. Oligochaeta

3. Hirudinea

4. Archiannelida

1.Polychaeta:

Locomotory Organs

The Polychaetes possess paired parapodia functioning as locomotry appendages,

are present only in the class Polychaeta.

Prostomium

Usually, there is a distinct head or Prostomium bearing sensory and feeding

appendages.

Mode of Life

The Polychaetes may be carnivorous, scavengers, or filter feeders.

Reproduction

The sexes are separate and fertilization of eggs takes place outside body. Their

free-swimming larva is called Trochophore.

Respiration

The respiration takes place through the body surface in many but in some gills,

may be present as respiratory organs.

Examples: Some well-known examples of marine polychaetes are Nereis,

Arenicola and Sabella. Nereis lives beneath stones and in crakes of rocks.



2.Class Oligochaeta:

Locomotory Organs

The Oligochaetes possess fewer numbers of Setae as compared to the

Polychaetes. The setae help the earth worms in crawling.

Sense Organs

There anterior end lacks eyes, or sensory appendages.

Clitellum

At sexual maturity, all of the oligochaetes develop in several segments,

glandular epithelium, called clitellum.

Mode of Life

• Oligochaetes live either in fresh water or on land.

• There is no free swimming larval stage in their development

• Majority of oligochaetes are scavengers, feeding on decomposing organic

matter.

• Some fresh water species feed on algae.

• Burrowers like earth worm ingest a large quantity of soil, digest the

organic matter and the living fauna.

Respiration

Respiration takes place through their general body surface. Some aquatic

species possess anal gills.

Economic Importance

Earthworms increase the fertility of soil by physically over turning it. They

ingest the soil, break it down and deposit it in the form of casts. The over turned

soil is relatively in proportions of total nitrogen, organic carbon, calcium,

magnesium and phosphorus.

3.Class Hirudinea:

Body Segments

Unlike polychaetes and oligochaetes, the number of body segment in leeches is

fixed at 34.

Suckers

The anterior and posterior body segments are fused to form suckers.



Locomotion

Leeches either swim or crawl.

Respiration

Respiration generally takes place through the body surface. Leaf like gills may

be present.

Parasitic Nature

Most leeches feed by sucking blood of aquatic invertebrates and vertebrates.

4.Archiannelida

• It is a small group of marine worms.

• They are not segmented externally and don’t have bristles.

• They live in the sea and show annelid characteristics to a minor extent.

• Their development is also characterized by Trochophore Larva.

Examples: Nerilla , Dinophilus

Phylum Mollusca (Shelled Animals)

Mollusca is the second largest phylum of the animal kingdom, and include

Slugs, Clams, Scallops and Squids.

Main Characters

Habit and Habitat

The majority of molluscs are marine. Some snails and clams inhabit fresh water

while slugs are terrestrial.

Nature

• Molluscs are primitively bilaterally symmetrical animals.

• Some molluscs serve as intermediate host of helminthes parasites and

some are destructive to wooden bottom of ship.

External Features

• The body is soft, unsegmented and consists of head, foot, mantle and

visceral mass.

• The body is clothed with a one layered epidermis.



• Body is commonly protected by an exoskeletal calcerous shell of one or

more pieces, secreted by Mantle.

• Head is distinct, bearing the mouth and provided with eyes, tentacles and

other sense organs.

Internal Features

• Visceral mass contains the organs of the body in compact form.

• Body cavity is hoemocoel.

• Digestive system-tract is simple.

• Circulatory system is open.

• The mouth in many species possesses a radulla, (a tongue like structure)

that can be protruded to scrape, tear or pull food.

• The respiration is by means of gills or lungs.

• The nervous system consists of cerebral ganglion, a pair of pedal cords to

the foot and a pair of visceral mass.

Reproduction

• Molluscs may have separate sexes or they may be hermaphrodite.

• The fertilized eggs give rise to a larva stage which transform into adult.

• Three types of larva trochophore, veliger and glochidium occur in

molluscs.

Classification Of Mollusca

The phylum Mollusca is divided into six classes:

1. Amphineura

2. Scaphopoda

3. Gastropoda

4. Bivalvia

5. Cephalopoda

6. Monoplacophora

Class Gastropoda



Example: This is the largest class of mollusca which included Snails, Whelks,

Conchs, Limpets, Cowries and Slugs.

Characters

• The gastropods are mostly marine, though some live in fresh water and a

few are terrestrial.

• The gastropods are asymmetrical.

• They have a well-developed head and a broad muscular foot.

• Both are on the ventral side of their body.

• Their visceral organs are located on the dorsal side and are enclosed in a

one-piece shell which is spirally coiled.

• The gastropods use the redula to scarp food particles or to drill holes in

the shells of bivalves.

• Some are carnivorous, a few are filter feeders.

Class Bivalvia

The class Bivalvia is the second largest class of the Phylum Mollusca.

• The bivalves are bilaterally symmetrical with a laterally compressed body

enclosed in a shell of two pieces (valves) hinged together.

• The shell can be opened or closed.

• By closing the shell tightly, the animals can protect itself off from

unfavourable environment or saves itself from predators.

• The head is rudimentary and the radula is absent.

• The foot is ventral, laterally compressed, usually wedge shaped.

Example: Bivalves include the Clams, Mussels, Oysters and Scallops. They are

mostly marine some live in fresh water but none is terrestrial.

Pearl Formation

• When a foreign particle living or dead enters a bivalve it causes irritation.

• The epithelial cells of the mantle start depositing concentric layers of

calcerous material around it, which ultimately forms a pearl.



• Pearl culture has been successfully carried out by artificially introducing

fragments of man-made hard material in pearl oysters.

• Pearls are formed both in marine as well as fresh water species.

Class Cephalopoda

• The cephalopods are all marine and exhibit a high level of development.

• Nautilus is the only living cephaloped that possesses a well-developed

external shell which is coiled and divided by transverse Septa in

chambers.

• The shell is reduced and overgrown by mantle in Squids and Cuttle fish.

• It is completely absent in Octopus.

Examples: Nautrilords, Squids, Cuttle fish, Octopus etc.

Class Monoplacophora

• They are primitive molluscs with a long fossil record.

• They have only one living representative, Neoporlina, which retains the

segmented characteristics of annelids, lost in all other molluscs.

Phylum Arthropoda (Jointed Appendages Animals)

Main Characters

• Arthropoda is the largest Phylum of the animal kingdom including 10,

00000 species of different types of animals.

• The word Arthropods is derived from Greek Arthos – Jointed and Podos

– Foot.

Habit and Habitat

Arthropodes have undergone an adaptive radiation for aerial, aquatic, terrestrial

and parasitic environment. They are widely distributed in each and every place

of the world.

Nature

Arthropoda are “bilaterally symmetrical,” metamerically segmented metazoa.



External Features

• Their body is covered by an exo-skeleton of “chitin” and protein.

• They possess paired jointed appendages.

• Their metamers are not alike but are specialized and their number is

generally fixed.

• The head is well developed.

Internal Features

• Musculature is not continuing but comprises separates striped muscles.

• The coelomic space in Arthropods is occupied by the blood vascular

system and is thus called “Haemocoel.”

• Digestive tract is complete; mouth and anus lie at the opposite end of the

body.

• Circulatory system is open with dorsal heart and arteries but without

capillaries.

• Respiration through general body surface, by gills in aquatic forms,

trachea or book lungs in terrestrial forms.

• Excretion by “Malpighian tubules” or Coelomoducts.

• Sexes are generally separate and sexual dimorphism is often exhibited by

several forms.

• Fertilization is internal.

• Development is usually indirect through the larval stage.

• Nervous system of arthropods is quite similar to that of annelids and

consists of dorsal anterior brain and a double ventral nerve cord.

Classification Of Arthropoda

Phylum Arthropoda is divided into following five classes:

1. Class Merostomata



• Almost all members of the class Merostomata are extinct. The only living

merostomes, the king Crabs have survived.

• The animals are horse-shoe shaped.

• The long spike like tail that extends, posteriorly is used in locomotion. It

is called “Telson.”

• They feed on mollusks, worms and other invertebrates that they find on

the ocean floor.

• King Crabs a hors-shoe crabs have a tough “Carapace” jointed to a

smaller abdomen.

• E.g:Limulus Polyphemus (King Crab).

2. Class Arachnida

• This class includes spiders, scorpions, mites, ticks and many other

terrestrial arthropods.

• The Arachnid body consists of a cephalothorax and abdomen.

• Cephalothorax is comprised of fused head and thorax.

• Arachnids have six pairs of jointed appendages.

• Most Archnids are carnivorous and prey upon insects and other small

arthropods.

• Respiration in archnids takes place either by trachea or book lungs or by

both.

• They are mainly terrestrial arthropods.

• They have no antenna.

• Cephalothorax is non-segmented.

• E.g: Scorpions, Ticks & Mites, Spiders

3. Class Crustacea



• They live both in marine and fresh waters.

• A few are terrestrial.

• Crustaceans are unique among arthropods in possessing two pairs of

antenna.

• They always have one pair of mandibles and two pairs of maxillae around

the mouth.

• Mandibles are usually adapted for biting and chewing. Maxillae are used

for holding the food.

• Their body is divided into three distinct parts, i.e. the head, thorax and

abdomen.

• Respiration usually takes place through gills associated with appendages.

• The sexes are usually separate and the reproduction is sexual.

• The thoracic and abdominal appendages may be variously modified for

walking, swimming, feeding, respiration or as accessory reproductive

structures.

• E.g: Sacculina (Parasitic Crustacean), Astacus (Cray-fish), Prawns,

Shrimps, Lobsters and Crabs etc.

4. Class Myriapoda

• All the animals are terrestrial.

• Their body is divided into a head and an elongated trunk with many

segments.

• Each segment bears one or two pairs of legs.

• They are carnivorous /herbivorous.

• Eyes may present or absent.

• E.g: Millipedes and Centipedes etc.

5. Class Insecta (Hexapoda) Insecta is the largest class of the animal kingdom.



Habit and Habitat

• In their adaptive radiation, approximately an 8,50,000 species of insecta

have occupied all types of terrestrial habitat.

• Some live in fresh water, however one small group is marine.

Nature and Adaptations

• The great success of insects can be attributed partly to the development of

flight in them.

• Flight has provided them the great capacity of dispersal, access to food

sources, and favourable habitat and escape from enemies.

• Corresponding to their number of species, there exists a huge variation in

their structural and biological adaptations.

External Features

• All insects have their body divided into three well-defined regions i.e. the

head, thorax and abdomen.

• There is always a pair of antenna on the head.

• The thorax always consists of three segments:

(a) Prothorax

(b) Mesothorax

(c) Metathorax

• Each thoracic segment bears a pair of legs.

• Head consists of six fused segments and a pair of compound eyes and

mouth parts.

• Abdomen comprises 7-11 segments and devoid of appendages.

Mouth Parts

The feeding appendages consists of three pairs:

(a) Mandibles

(b) First Pair of Maxilla

(c) Second Pair of Maxilla

• The second pair of maxillae have fused together to form the “LABIUM,”

or lower lip



• The upper lip is formed by the projections head and is called the

“LABRUM.’

Types: The mouth appendages have been greatly modified to form five basic

types of pattern:

(i) Biting

(ii) Chewing

(iii) Piercing

(iv) Sucking

(v) Siphoning or Sponging

Internal Features

• Heart is elongated, tubular and divided into chambers situated in the

abdomen.

• Excretion takes place through “Malpighian tubules.”

• Liver is absent but salivary glands are usually present.

• Respiration is by “Trachea”. External gills may be present as accessory

respiratory organs in some aquatic insects.

Reproduction

Reproduction is sexual in most insects. However, it takes place

parthenogenetically i.e. eggs developing without being fertilized by sperms in a

number of insects e.g: Aphids and Termites etc.

Metamorphosis

The development of insects after hatching from egg into adult stage involves

considerable growth and in some cases drastic morphological changes.

• The entire post-hatching development is termed as “Metamorphosis.”

(A) Incomplete Metamorphosis

• In some insects, the immature form that hatch from the egg are essentially

similar in shape to their adults, but are smaller in size, lack wings and

reproductive organs



• They attain adult characters after some growth period. This type of

metamorphosis is called “Incomplete Metamorphosis.”

• Three stages are Egg → Nymph → Adult.

• For example, Cockroach, Grasshopper, Bugs etc.

(B) Complete Metamorphosis

• In this type the animal shows following stages during its complete

development: Egg → Larva → Pupa → Adult.

• For example, Mosquito, Butter fly, House fly etc.

Economic Importance of Insects

Insects are of very great importance to man.

Beneficial Insects

1. Apis, the honey bees produce honey and also give wax.

2. Insects bring about the cross-pollination.

3. Bombyx and Eupterote are silk-moths and produce silk.

4. The larvae of Lucilla and Pharmia are used in wound healing of bones.

5. Some insects feed upon and destroy harmful insects.

6. Some insects are Scavengers

Harmful Insects

1. Many types of mosquitoes, flies, fleas, lice and bugs transmit diseases to man

and animals.

2. Human food is spoiled by cockroaches, ants and flies.

3. Tinea and Teniola are cloth-moths and destroy cloths.

4. Tenebrio is mealworm. They eat meal, flour and grains.

5. Lepisma destroy the books.

6. Termites destroy books and wood.

7. Many insects injurious to crops e.g. Tree hoppers, Leaf hoppers, Aphids,

White flies and bugs.

Phylum Echinodermata

General Characters



Habit and Habitat

The Echinodermates are exclusively marine including the largest invertebrate

“Giant Squids.”

External Features

• Symmetry usually radial, nearly always pentamerous.

• Body shape is rounded to cylindrical or star like.

• Surface of the body is rough.

• Body wall consists of an outer epidermis, a middle dermis and inner

lining of peritoneum.

Internal Features

• Endoskeleton consists of closely fitted plates forming shell usually called

“Theca,” may be composed of separate small “Ossicles.”

• Coelom is spacious, lined by peritoneum and occupied mainly by

digestive and reproductive systems.

• Presence of “Water Vascular System” is most characteristic feature.

• Alimentary tract is usually coiled.

• Circulatory or Haemal or blood lacunar system is typically present.

• Excretory system is wanting.

• Nervous system is primitive, consists of ganglionated nerve cord.

• Sense organs are poorly developed.

• Sexes are usually separate.

• Reproduction is usually sexual, fertilization is external.

Water Canal System

Water canal system is unique in possessing an internal closed system of canals

containing a watery fluid.

Regeneration



Regeneration of lost part is common

Importance of Water Canal System

These canals are provided with tubular protrusions called “Tube Feet,” which

serve a number of functions like locomotion, anchoring to hard surfaces,

grabbing the prey, diverting food particles towards mouth and in some cases

also respiration. The watery fluid is drawn from the surrounding water through a

perforated disc called the “Madreporite.”

Example: Star Fish, Brittle stars, Sea urchins, Sea-cucumbers, Sea-Dollar, Sea-

lilies and Feather stars.

Larva

Bipinnaria larva

Phylum Hemichordata

Friendsmania.net

General Characters

• It is a small group of animals, which include about 90 species.

• They are soft-bodied animals, which usually live in shallow “U” shaped

burrows in the sandy or muddy sea bottom.

External Features

• They are cylindrical or vase shaped animals, bilaterally symmetrical and

lack any segmentation.

• They may be solitary or colonial and usually range between a few

millimeter and 250 cm in length.

• Sexes are separate in hemichordates.

Internal Features

• Circulatory system is open and coelom is divided into three chambers.

• A dorsal and a ventral nerve cord are present.

Larva

Tornaria larva

Example: Balanoglossus, Acron worm etc.



CHAPTER 11

BIO-ENERGETICS

Definition:

The capturing and conversion of energy from one form to another in the living

system and its utilization in metabolic activities is called Bioenergetics.

Bio-energetics is the quantitative study of energy relationships and conversion

into biological system. Biological energy transformation always obeys the laws

of thernodynamic.

Role of Atp As Energy Currency

Atp is adenosine triphosphate. Adenosine is made of adenosine and ribose

sugar. Among the three phosphate groups two are energy rich PO4 bonds. So,

ATP is a high-energy compound it gives its PO4 groups easily. When 1 Atp is

converted into Adp, 7.3 K cal/mole or 31.81 KJ/mole energy is released. Atp ->

Adp + Pi + Energy



Living organisms use organic food for generation of energy. These foods

usually contain carbohydrates which degrade to produce CO2, H2O and energy.

Which is usually in the form of ATPs. ATP plays role in several endergonic and

exergonic reactions.

Endergonic Reactions

Those chemical reactions which accompanied by the absorption of the energy

are known as endergonic reactions. The products have a higher free energy than

reactants. Examples of endergonic reaction in human are;

1. Synthesis of proteins

2. Synthesis of lipids

3. Synthesis of cholestrol

4. Synthesis of glycogen

Exergonic Reactions

Those reactions which complete along with the liberation of free energy are

known as Exergonic reaction. The products have a lower free energy than the

reactants.

Example: An aerobic glycolysis, Kreb’s cycle, oxidative phosphoylation.

Pigments

Substances in plants that absorb the visible light are called Pigments. Different

pigments absorb light of different wavelength. They are involved in the

conversion of light energy to chemical energy. Important plant pigments are

chlorophyls, carotenoids, phycobilin, xanthophylls, phaelophytin.

Photosystem

Each photosystem is a highly-organized unit consisting of chlorophyll accessory

pigment molecules and electron carrier molecules present on the thylakoids of

chloroplast. Each thylakoid contains many units of two photosystems the

photosystem I and photosystem II. So, chloroplast contains thousands of

photosystems.

The photosystem consists of chlorophyll “a” and “b” and carotenoids.

Chlorophyll having empirical formula of C55H72O5N4Mg is almost identical to

“Chlorophyll b” of empirical formula C55H70O6N4Mg. But the slight structural

difference between them is enough to give 2 pigments slightly different

absorption spectra and hence different colours “Chlorophyll a” is blue green

while “b” is yellow green.



Hundreds of chlorophylls a, chlorophyll b and carotenoids cluster together in a

photosystem. But only a single molecule of chlorophyll a acts like a reaction

centre the rest of others absorbs a photon, the energy is transmitted from pigment,

molecules to pigment molecules until it reaches a particular chlorophyll a located

in the region of reaction centre, where it gives electrons to primary electron

acceptor.

Hundreds of carotenoids are admixed with 2 types of chlorophyll molecules in

photosystem, giving yellow and orange shades. Carotenoids can absorb

wavelength of light that chlorophyll cannot transfer to chlorophyll a. Sometimes

excess energy can damage chlorophyll a, so carotenoids accept energy from them,

thus providing a function known as Photoreceptor.

Role Of Light

Light has a dual nature, can behave like a wave or like a particle. It is composed

of packets of energy called photons (hu). Light energy captured in the light

harvesting complexes is efficiently and rapidly transferred to the chlorophyll

molecules present in the photosynthetic reaction centre. When a photon of light

hits these chlorophylls a molecule. The energy of these photons is absorbed and

results in the elevation of an e- from the ground state to an excited state, level

depends upon the energy and incident photon.

A photon of red light has enough energy to raise an electron to excited state I

and this energy is sufficient to carry out all the chemical reactions of

photosynthesis.

The energy transferred by blue light raise the electron to excited state –2.

However, the energy transmitted by red or blue photons to photosynthetic

electron transport chain is exactly the same. This is because that extra energy is

lost (from absorption of blue photon) by radiationless de-excitation.

The excitation energy can be used in

1. Photochemistry (i.e. it enters the photosynthetic electron transport chain)

2. Lost as heat.

3. Give fluorescence etc.

Photosynthesis

Photosynthesis is an anabolic process in which chloroplast of the plants take up

CO2 and H2O and using light energy to synthesize carbohydrates. In

photosynthesis, the light energy is converted to chemical energy. It is an

oxidation reduction process in which water is oxidized and CO2 is reduced

6CO2 + 12H2O -> C6H12O6 + 6H2O + 6O2 ↑



In simple

6CO2 + 6H2O -> C6H12O6 + 6O2 ↑

This process divides into

1. Light reaction

2. Dark reaction

1. Light Reaction

In the light dependent reactions, light energy is absorbed by chlorophyll and

other photosynthetic pigment molecules. It is then converted into chemical

energy. Due to this energy conversion, NADPH+ and ATP are produced.

Components of Light Reaction

1. Light capturing chlorophyll molecules.

2. Membrane bound protein complexes

3. Mobile electron carriers

Chlorophyll Molecules and Photosystem

Each photosystem consists of a light gathering “antenna complex” and a “reaction

centre”. The antenna complex has many molecules of chlorophyll a, chlorophyll

b and carotenoids most of them channeling the energy to reaction centre. Reaction

centre of photosystem I and II has one or two “chlorophyll a” molecules, primary

electron acceptor, associated electron carriers of electron transport system and

certain specific proteins known as chlorophyll-bound proteins which differs them

from other “chlorophyll a” molecules of the same system. The “chlorophyll a”

molecules at the reaction centre of photosystem I (PSI) has a maximum

absorbance at 700 nm, while those of PS II absorb at 680 nm. Therefore, these

reaction centre are called P700 and P680 where P simply stands for pigment.

Complexes

There are 4 major groups of complexes.

1. PS I

2. PS II

3. Cytochrome b/f complex

4. ATPase complex

The PS I and ATPase or ATP synthase complex are present on non-appressed

region of thylakoid. While PS II and light harvesting complexes (LHC II) are

present on appressed side. The cyt b/f complex is randomly distributed

throughout the mambrane.



Mobile Electron Carriers

Transport the excited electrons between the complexes. These are plastoquinone

(PQ) plastocyanin (PC), ferredoxin (FD)

Electron Transport

This process occurs in several steps.

(1) Excitation Of Ps Ii

When chlorophyll a of reaction centre of PS II is striked by a photon, the energy

of photon absorbs in it. This results in the elevation of an electron from the ground

state to an excited state. The excited electrons produced within P680 is rapidly

transferred to the primary electrons acceptors phaelophytin. So, 2 electrons which

are transformed has to be replaced which is done by water.

(2) Photolysis Of Water

In the presence of light a water splitting enzyme complex extracts 4 electrons

from two water molecules. Removal of electrons splits the water into two

hydrogen ions 2H+ and oxygen atoms. The extracted electrons from water are

supplied to PS II (P680) while the oxygen atom immediately combines with

another oxygen atom to form O2. Which is released during photosynthesis. The

hydrogen ions or proton (H+) are stored in thylakoid space. The overall reaction

will be;

2H2O -> 4 H+ + 4e- + O2

(3) Flow Of Electrons From PS II To PS I

Photoexcited electrons accepted by phaelophytin from PS II are transferred to

plastoquinone molecules QA and QB which accept two electrons and takes up

two protein from the stroma. PQ carries electrons from PS II to cytochrome b/f

complex containing FeS protein. This is thought to be the rate limiting step of

electron transport. Electrons from PQ are taken up by Cyt b/f complex through

FeS and releasing protons (2H+) to the lumen. The second mobile electron carrier

plastocyanin (PC) takes the electrons and delivered to the photosystem I.

(4) Flow Of Electrons From PS I To Nadp+ Reductase

A second excitation event within PS I leads to the transfer of electrons to the

primary electron acceptor. The primary e- acceptor of PS I passes the

photoexcited electrons to a second electron transport chain, which transmit then

to ferredoxin, an iron containing protein. An enzyme called NADP reductase then

transfer the electrons from Fd to NADP+ (oxidized form).

(5) Reduction Of Nadp+ To Nadph+ H+



This is the redox reaction that stores the high-energy electrons in Nadp+ to

reduced it to Nadph + H+.

Nadp+ + 2H+ -> Nadph + H+

Hydrogen ions are taken from stroma which is being pumped from thylakoid

space to stroma by ATPase.

Photophosphorylation

Hydrogen ions are pumped into thylakoid space by cyt b/f and also 2H+ ions are

collected there from photolysis of one water molecule. This large no. of H+ ions

in thylakoid space compared to stroma, creates an electrochemical gradient, when

these hydrogen ions flow out of the thylakoid space by way of a channel protein

present in membrane called the ATP synthase complex, energy is prvided to it.

The transport of 3 protons (H+ ions) through the ATPase complex are normally

required to produce 1 ATP from ADP and inorganic phosphate Pi.

ADP + Pi -> ATP

This is called chemiosmotic ATP synthesis because chemical and osmatic

events join to permit ATP synthesis. The linear flow of electrons from H2O to

NADP+, coupled to ATP syntheses is non-cyclic photophosphorylation because

the electrons pass on to a terminal acceptor.

In cyclic photophosphorylation, the electrons are cycled from PS I back to PQ.

So only ATP is produced but not NADPH + H+. This occurs under following

conditions to meet increased ATP demand for e.g. CO2 fixation

1. Protein synthesis

2. Synthesis of starch

Events Of Light Reaction

1. Photolysis of water.

2. Reduction of NADP+ to NADPH + H+

3. Synthesis of ATP by photophosphorylation.

So, during light reaction ATP and NADPH + H+ are produced which are used

in Dark reaction, O2 is evolved as a byproduct.

2. Dark Reaction

The dark reaction consists of a series of light independent reactions which can

proceed even in the absence of light. During dark reaction, energy is produced

by ATP and NADPH+ H+ and CO2 is fixed in carbohydrates. This cyclic series



of enzymatic catalyzed reaction in the stroma of the chloroplasts is called

Calvin-Benson Cycle. During this cycle CO2 is reduced to triose-PO4 sugars,

therefore this pathway is also known as C3 pathray (reductive pentose phosphate

cycle) and the plants undergo this cycle are known as C3 plants. The calvin or

C3 cycle is divided into 3 phases.

Carboxylation (Carbon Fixation)

The calvin cycle begins when a molecule of CO2 reacts with a highly reactive

phosphorylated five carbon sugar named ribulase 1.5 bisphosphate (RuBP). This

reaction is catalyzed by the enzyme ribulase biphosphate carboxylase or Rubisco

(it is the most abundant protein in chloroplast). The product of this reaction is a

highly unstable, six carbon intermediate that immediately breakdown into two

molecules of three carbon compound called 3-phosphoglycerate (G3P).

3CO2 + 3RuBP -> G3P

Reduction

Each molecule of the PGA or G3P receives an additional phosphate from ATP

of light reaction, forming 1,3-bisphosphoglycerate (G1,3P) which is then

reduced to glyceraldehyde 3-phosphate (GA3P) and Dihydroxyacetone

phosphate (DHAP) by NADPH+ H+GA3P and DHAP are interconvertible and

the reaction don’t require any energy. These products are also formed during

glycolysis and links dark reaction with sugar synthesis pathway.

6G3P + 6ATP + 6NADPH + H+ -> 6GA3P + 6ADP + 6NADP+ + 6Pi

Regeneration

Three carbon compounds are rearranged to form five carbon units’ ribulose 1,5-

bisphosphate (RuBP), which is the primary carbon acceptors in the cycle.

5 GA3P + 3ATP -> 3 RuBP + 3 ADP + 3Pi

Again, more molecules of ATP are used for phosphorylation of RuBP, which

then starts the cycle again.

Conclusion

For every 3 molecules of CO2 entering the cycle and combining with 3 moles of

RuBP (5C), six molecules of three carbon G3P is produced. Out of six G3P only

one G3P molecule leaves the cycle and can be used for synthesis of glucose,

starch, cellulose, sucrose or other compounds. The other 5 molecules are

recycled to regenerate 5C RuBP’s three molecules, the CO2 acceptor.

Consumption

For the net synthesis of one G3P molecule, the calvin cycle consumes a total of

nine ATP’s and six NADPH + H+



Photorespiration

In presence of light (photon), oxygen is taken up by RuBP and CO2 is evolved.

RuBP + O2 -> PGA + Phosphoglycolate ® CO2

It occurs when CO2 is deficient, Rubisco works like an oxygenase rather than

carboxylase in presence of O2, produce phosphoglycerate (phosphoglyceric

acid-PGA) and Phosphoglycolate, where phosphoglycolate rapidly breaks down

to release CO2. Alternative mechanisms of carbon fixation in hot, arid climate.

In hot temperature, the concentration of CO2 begins to fall in leaves due to

closing of stomata, increase yield of photosynthesis etc. These conditions in

leaves may cause a wasteful process called photorespiration in which precious

products are lost and less energy is generated. In certain plant species, alternate

mode of CO2 fixation has evolved even in very hot and arid environment.

These two photosynthetic adaptations are;

1. C4 Photosynthesis (C4 Pathway)

This process occurs in C4 plants. Those which prefer calvin cycle with an

alternate mode of carbon fixation are known as C4 plants. CO2 reacts with PEP

in presence of PEP carboxylase to produce oxaloacetate, a four-carbon

compound which converts into malate. Malate transfers from mesophyll cell to

bundle sheath cell where it breaks down to pyruvate and releases CO2. This CO2

is fixed in calvin cycle by Rubsico and so the cycle continues.

E.g. Family poaceae especially sugar cane, corn.

2. CAM

Plants of hot, arid environment, open their stomata during the night and close

them during the day. Closing stomata during the day helps deserts plants to

conserve water but it also prevents CO2 from entering the leaves. During the

night, when their stomata are open, these plants take up CO2 and incorporate it

into a variety of organic acids because of lack of energy (ATPs and NADPH+

H+). This mode of carbon fixation is called crassulacean acid metabolism (CAM).

They store these organic acids in vacuoles. During day time, organic acids release

CO2 for dark reaction because light reaction can supply ATP and NADPH+ H+

on which the calvin cycle depends.

E.g. Cactus, Pinapple, Succulent plants.

Cellular Respiration



Aerobic breakdown of glucose molecules into CO2 and water with synthesis of

ATP is called Cellular Respiration.

C6H12O6 +6O2 -> 6CO2 + 6H2O + 673 Kcal/mole

Respiration is an oxidation reduction process because the carbon of substrate,

mostly glucose is oxidized to form CO2, while the atmospheric O2 is reduced to

form the water.

There are two types of cellular respiration.

(A) Aerobic Respiration

The breakdown of sugar, in presence of oxygen [molecular O2 and release of

carbon dioxide and water with sufficient amount of energy. This type of

respiration is known as Aerobic respiration, and the organisms performed this

are known as Aerobes.

(B) Anaerobic Respiration

The breakdown of sugar in absence of oxygen is known as Anaerobic

respiration, and this type of respiration is performed by Anaerobs.

E.g. Yeast, some bacteria, gut parasites (e.g. tapeworm). Some species of

annelids, roots of plants growing in water logged area. Anaerobes are of two

types. Those which never need of O2 at all are Obligate anaerobes. Those which

respire aerobically but can also respire in absence of O2 are known as

Facultative aerobes.

Categories Of Aerobic Respiration

The process of aerobic respiration is divided into three main categories.

1. Glycolysis

2. Kreb’s cycle

3. ETC

(1) Glycolysis

Glycolysis is the first and common step in both aerobic and anaerobic respiration.

It consists of a complex series of enzymatically catalyzed reactions in which a 6-

carbon molecule “Glucose” breaks down into 3 carbon “Pyruvic acid”. These

reactions occur in Cytoplasm and doesn’t require oxygen. Following are the

different steps of Glycolysis.

(I) Phosphorylation



Phosphorylation is the addition of phosphate groups to the sugar molecules.

Glucose is phosphorylated by a molecule of ATP to form an activated molecule,

the glucose 6 phosphate. ATP is converted to ADP.

(II) Isomerization

Glucose -6-phosphate is converted to fructose -6-phosphate, an isomer of it by

an enzyme.

(III) Second Phosphorylation

Another molecule of ATP is invested which transfers its phosphate group to

carbon no.1 of fructose –6-phosphate, forming fructose 1,6-bisphosphate and

ADP.

(IV) Cleavage

The 6-carbon, fructose 1,6 bisphosphate molecules is break down into 2; three

carbon molecules, 3-phosphoglyceraldehyde PGAL and dihydroxyacetone

phosphate (DHAP). These two sugar molecules are isomers and are

interconvertible. This is the reaction from which glycolysis derives its name.

DHAP is converted to its isomer PGAL and then 2 PGAL will be converted to 2

pyruvic acid molecules. Since at this stage 2 ATPs are used, therefore this phase

is known as Energy investment phase.

In the subsequent reactions, energy is produced therefore this half is also known

as Energy yielding phase

(V) Dehydrogenation (Oxidation)

In the next step, PGAL is acted upon by an enzyme dehydrogenase along with a

co-enzyme nicotine amide adenine dinucleotide (NAD+), which convert PGAL

into phosphoglyceric acid PGA or phosphoglycerate by the loss of two

hydrogen atoms (2e- + 2H+). These H atoms are captured by NAD+. This is a

redox reaction in which PGAL oxidized by removal of electrons and NAD is

reduced by the gaining of electrons. Now phosphoglyceric acid PGA picks up

phosphate group (Pi) present in cytoplasm and becomes 1,3-bisphosphoglyceric

acid (DPGA).

(VI) Phosphoryl Transfer

1,3-bisphosphoglyceric acid loses its phosphate group to ADP forming ATP and

3-phosphoglyceric acid.

(VII) Isomerization

The PO4 group of PGA, attaches with carbon no,3 changes its position to carbon

no.2 forming an isomer 1-phosphoglyceric acid.



(VIII) Dehydration

A water molecule is removed from the substrate and forming phosphoenal

pyruvate (PEP).

(IX) Phosphoryl Transfer

ADP removes the high energy PO4 from PEP producing ATP and Pyruvic acid.

OVERALL REACTION of glycolysis can be summarized as Glucose + 2ADP

+ 2NAD+ -> 2 Pyruvic acid + 2ATP + 2NADH+ H+ + 2H2O

Energy Yield

Since when PGAL is produced, the cycle is counted twice because DHAP also

converts into PGAL and enter the same cycle. 4ATP molecules are produced at

Substrate level phosphorylation because PO4 groups are transferred directly to

ADP from another molecule. 2 ATP are used in the first phase. Thus, there is a

net gain of 2 ATPs. 2 NADH+ H+ are produced and each gives 2 ATPs (a total

of 6 ATPs). Therefore, net production of ATP during glycolysis is 8 ATPs

Fate Of Pyruvic Acid

There are 3 major pathways by which it is further processed under anaerobic

conditions, pyruvic acid either forms, ethyl alcohol or lactic acid or produces

CO2 and H2O from kreb’s cycle under aerobic conditions.

Fermentation

Fermentation the alternative term for Anaerobic respiration was used by

W.Pasteur and defined as respiration in absence of oxygen (air). The production

of ethyl alcohol from glucose is alcoholic fermentation and that of lactic acid is

lactic acid fermentation.

Alcohol Fermentation

Each pyruvic acid molecule is converted to ethyl alcohol also known as Ethanol

in two steps. In the first pyruvic acid is decarboxylated to acetaldehyde under

the action of enzyme.

Pyruvic acid CH3.CO.COOH -> CH3CHO + CO2

In the next step NADH+ H+ reduces acetaldehyde to ethyl alcohol

CH3.CHO + NADH+ H+ -> CH3.CH2OH + NAD+

Ethyl alcohol is toxic, plants can never use it because it cannot be converted to

carbohydrates or breaks up in presence of O2. When accumulation is more than

tolerable limits, plants will be poisoned and subsequently they died.



Lactic Acid Fermentation

When NADH+ H+ transfer its hydrogen directly to pyruvic acid, it results in

formation of lactic acid.

Pyruvic acid + NADH + H+ -> CH3.CH.OH. COOH

During extensive exercise, such as fast running muscle cells of animals and man

respire anaerobically. Due to inadequate supply of O2, pyruvic acid is converted

to lactic acid. Blood circulation removes lactic acid from muscle cells. When

lactic acid accumulates inside cells, it causes Muscle futigue. This forces person

to stop work, until normal O2 levels are restored.

Economic Importance Of Fermentation

1. It is the source of ethyl alcohol in wines and beers Wines are produced by

fermenting fruits like grapes, dates etc. Beers are produced by fermenting

malted cereals such as Barley.

2. Yeast is used to prepare bread from wheat.

3. Milk is converted to curd (yoghurt) by bacteria.

4. Preparation of cheese and other dairy products.

5. Production of lactic acid, propionic acid, and butanol.

6. Flavour of pickles is due to lactic and acetic acid.

7. Addition of lactic and acetic acids prevent foods from spoilage and also give

sour flavours to yoghurt and cheese.

8. Acetone is also formed as a by-product.

(2) Kreb’s Cycle

Formation Of Acetyl-Coa

Before entering the Kreb’s cycle, each molecule of pyruvic acid undergoes

oxidative decarboxylation. During this process one of the three carbons of

pyruvic acid molecule is removed to form CO2 by enzymatic reactions.

Simultaneously pyruvic acid is oxidized and a pair of energy rich Hydrogen

atoms are passed on to a H acceptor NAD+ to form NADH+H+. The remaining

2-carbon component is called acetyle which combines with coenzyme A to form

an activated two carbon compound called acetyle CoA. “Acetyle CoA connects

Kreb’s cycle with glycolysis.” For each molecule of glucose that enters

glycoilysis, two molecules of acetyle CoA produced, which enter in a cyclic

series of enzymatically catalyzed reactions known as Kreb’s Cycle, which

occurs in Mitochondria.

Pyruvic acid (3C) + CoA + NAD+ -> Acetyle CoA + CO2 + NADH+H+

Series Of Reactions In Kreb’s Cycle



Sir Hans Kreb was working over these cyclical series of reactions therefore the

cycle was given the name as Kreb’s cycle. The first molecule formed during the

cycle is citric acid, so it is also called as “Citric Acid cycle.” This cycle is a

multi-step process and the steps are given below:

1. Formation Of Citric Acid

In this first step of the Kreb’s cycle, bond between acetyl and CoA is broken by

the addition of water molecule. The acetyl (2C) reacts with 4 carbon compound

(oxalo acetic) acid to form 6-carbon compound, citric acid, and the CoA is set

free. This citric acid possesses 3 carboxyl groups, therefore the cycle is also

recommended as Tricarboxylic Acid Cycle (TCA cycle).

2. Isomerization

A molecule of water is removed and another added back so that cirtic acid is

isomerized to isocitric acid through an intermediate, Cis-aconitic acid.

3.First Oxidative Decarboxylation

First time the sugar molecules are oxidized, therefore it is also called first

oxidation of the cycle. Isocitric acid is oxidized yielding a pair of electrons

(2H+) that reduces a molecule of NAD+ to NADH+H+. The reduced sugar

molecule is decarboxylated with the removal of CO2. It now converts into a 5-

carbon compound α-Ketoglutaric acid (αKG).

4. Second Oxidative Decarboxylation

αKG is oxidatively decarboxylated. A CO2 molecule is lost. The remaining 4-C

compound is oxidized by transfer of a pair of electrons (2H+) reducing NAD+

to NADH+H+. This 4-C compound accepts CoA forming succinyl CoA.

5. Substrate Level Phosphorylation

Bond between succinyl and CoA is broken. CoA is replaced by PO4 group,

which is then transferred to Guanosine diphosphate (GDP) to form Guanosine

Triphosphate (GTP). GTP then transfers its phosphate group to ADP, forming

ATP and with addition of 1 water molecule, succinic acid is formed.

6. Third Oxidation

With loss of two electrons (2H+) succinic acid is oxidized to fumaric acid and

FAD+ is reduced to FADH2.

7. Hydration

One water molecule is added to fumaric acid to convert it to Malic acid.



8. Fourth Oxidation and Regeneration Of Oxalo-Acetic Acid

Oxidation of malic acid leads to the production of 1 more NADH+H+ and

oxaloacetic acid is regenerated.

Energy Yield

Glucose molecule breaks down into 2 pyruvic acid molecules and each will

enter the Kreb’s cycle.

For each pyruvic acid molecule, 3CO2 molecules are produced, four NADH+H+

are produced and 1 FADH2.

Pyruvic Acid + 3H2O + 4NAD+ + FAD+ -> 3CO2 + 4NADH+H+ + 1FADH2

Four calculation of energy (ATPs) we will multiply the products with 2 as 2

acetyle CoA enters the Kreb’s cycle.

Pyruvic Acid to Acetyl CoA..............1NADH2 -> 3ATP x 2 = 6 ATP

Kreb’s Cycle......................................3NADH+H + -> 9ATP x 2 = 18 ATP

.................................................. ....1FADH2 -> 2ATP x 2 = 4 ATP

......................S ubstrate Level Phosphorylation -> 1ATP x 2 = 2ATP

Total..................................... = 30 ATP

Overall Energy Yield of Aerobic Respiration

Glycolysis..............................8ATP

Pyruvic Acid to Acetyl CoA..............6ATP

Kreb’s Cycle............................24 ATP

Total...................................38 ATP

But actually 2 ATPs are utilizing in transporting cytoplasmic NADH+H+ to

Mitochondria, which are produced during Glycolysis, so overall energy yield is

only 36 ATPs.

3. Electron Transport Chain/ Etc Or Et System



The last of all steps is ETC. It consists of a series of electron acceptors which

are located in the cristae of mitochondria. In respiration, there are 6 steps at

which hydrogen atoms are released (one in glycolysis, 5 in Kreb’s cycle). A pair

of hydrogen atoms are dissociated into a pair of electrons and a pair of protons.

2H -> 2H+ + 2e

These electrons are accepted by Nicotinamide adenine dinucleotide (NAD) and

Flavin Adenine Dinucleotide (FAD) from where they are passed along a chain

of electron carriers such as cytochrome b, cytochrome c; cytochrome a,

cytochrome a3. While passing from one carrier to another, these cytochromes

are alternatively reduced and oxidized. During this, the energy released is used

in the formation of ATP (adenosine triphosphate) from ADP and Pi. The final

electron acceptor is atmospheric oxygen, which also picks up protons, and form

the water molecule. The formation of ATP in mitochondria is called Oxidative

Phosphorylation.

From every NAD, 3ATPs and from 1 FADH2, 2 ATPs are produced.

CHAPTER 12

NUTRITION

Nutrition In Plants

Classification On The Basis Of Mode Of Nutrition

Plants can be divided into two groups on the basis of their mode of nutrition.

1. Autotrophic

2. Heterotrophic

1. Autotrophic Nutrition

Definition:

“Autotrophic nutrition is the type of nutrition in which organic compounds are

manufactured from available inorganic raw material taking from surroundings”.

In autotrophic nutrition, the nutrients do not require to be pretreated or digested

before taking them into their cells.



Two Methods Of Autotrophic Nutrition

On the basis of source of energy, autotrophic nutrition can be sub-divided into

following sub-types.

(I) Phototrophic nutrition

(II) Chemotrophic nutrition

I. Phototrophic Nutrition

Definition:

“The type of autotrophic nutrition is which organic molecules are manufactured

from simple inorganic molecules by using light energy as a source is called

Phototrophic Nutrition”.

Example

a. Green Plants

b. Photosynthetic Bacteria

(I-A) Phototrophic Nutrition In Green Plants

Green plants are very prominent example of phototrophic nutrition. They

prepare the food by the process of photosynthesis.

Raw Material

The raw material needed by these organisms are;

(1) CO2 AND H2O

They provide carbon, hydrogen and oxygen for the synthesis of organic

molecules.

(2) Minerals

The minerals like Nitrogen, Phosphorus and Sulphur and Magnesium are also

required.

(3) Green Pigments

The green pigments i.e. Chlorophyll a, b, or others are also required to absorb

the energy from universal source of light.

(4) Light

In the presence of sun light nutrients are used to synthesis the energy rich

compounded (CHO) This process is called “PHOTOSYNTHESIS”.

This process can be represented by equation as follows.

6CO2 + 12H2O -> C6H12O6 + 6O2 + 6H 2O



(I-B) Phototrophic Nutrition in Photosynthetic Bacteria

Photosynthetic bacteria are unique because they are the only organisms which

are capable of synthesizing the carbohydrate food without chlorophyll “a”.

Differences Between Photosynthetic Bacteria And Green Plants

• Photosynthesis in bacteria is different from green plants. Some

differences are

• Photosynthetic bacteria usually grow in sulphide spring where H2S is

normally present.

• Hydrogen is provided by H2S instead of H2O.

• Free oxygen is not released as a byproduct in bacterial photosynthesis.

• The process takes place at low expenditure of energy.

Two Types Of Photosynthetic Bacteria

There are two types of photosynthetic bacteria.

(1) Those in Which “S” Is Released as By Product

These bacteria use H2S as donor of hydrogen. Light splits hydrogen sulphide.

Hydrogen combines with CO2 to form H2O.

2H2S + CO2 -> (CH2O)n + H2O + 2S

Examples: Purple Sulphur Bacteria ® which use Bacterio Chlorophil &

Caretenoid as photosynthetic pigments.

(2) Those in Which “S” Is Not Released as By Product

These bacteria use H2S as Hydrogen donor whereas Sulphur is not the by

product in their case.

Examples

• Purple Non-Sulphur Bacteria

• Brown Non-Sulphur Bacteria

Both of these contain “Bacterio Chlorphyll” as photosynthetic pigments.

(II) Chemotrophic Nutrition

Definition:



“The mode of autotrophic nutrition in which organic molecules are

manufactured from simple inorganic molecules by using energy produced by

the oxidation of certain inorganic substances such as ammonia, nitrates, nitrites,

ferrous ions, H2S and etc. This type of nutrition is called Chemotrophic

Nutrition and process of manufacturing food is called Chemosynthesis.”

Mainly Bacteria are

Ammonia Using Bacteria

They derive their energy by oxidation of Ammonia.

NH2+ + O2 -> 2NO2 + 2H2O + 4H+ + energy

Bacteria Converting Nitrites to Nitrates

2NO2 + O2 -> 2NO3- + energy

Importance of Chemosynthetic Bacteria

The chemosynthetic bacteria that act on nitrogen compounds do play an

important role in the maintenance of nitrogen balance in the life system.

2. Heterotrophic Nutrition in Plants

Definition:

“Plants which are not capable of manufacturing their own organic molecules

entirely or partially depend for these organic molecular are called

“Heterotrophic Plants”

Classification of Heterotrophic Plants

On the basis of type of organisms on which heterotrophic plants depend, they

can be classified into following two classes.

1. Parasitc Plants or Parasites

2. Saprophytic Plants or Saprophytes

1. Parasites

Definition:

"Those heterotrophic plants which depend on living plants and animals for their

nutritional requirements are known as Parasites."

Types Of Parasites

Parasitic plants can be divided into following types.

A. Obligate or total parasites.

B. Facultative or partial parasites.

1.A Total Parasites



Definition:

Those parasites which depend for their nutrition entirely on other living

organisms.

Classification of total Parasitic Angiosperms

Total or obligate parasitic angiosperms are broadly classified into

• Total stem parasite

• Total root parasite

Total Stem Parasites

Definition:

“Those parasitic plants which depend entirely on the stems of other plants are

called “Total stem Parasites”

Explanation

These plants send Haustoria (specialized structures for absorbing nutrients in

parasitic plants) inside the tissue of host. The xylem of parasite comes in contact

with xylem of host and phloem of parasite to phloem of host. Through xylem it

sucks the water and nutrients, through phloem prepared organic material. The

host plant eventually dies off due to exhaustion.

Example: Cuscuta (Amer-Bail)

Total Root Parasites

Definition:

"Those parasitic plants which suck their nutritional requirements from the roots

of host are called “Total root parasites”.

Examples

• Orobanche -> attacks the roots of the plants belonging to families

Cruciferae and Solanaceae

• Cistanche -> Parasitizes on the roots of Calatropis.

• Striga -> Found as parasite on the roots of sugar cane

(1.B) Partial Parasites

Definition:

“Those parasite plants which depend for their nutritional requirements partially

on other living organisms are called Falcultave or partial parasites."

Classification of Partial Parasitic Angiosperms



Partial parasitic angiosperms can be broadly classified into

• Partial Stem Parasite

• Partial Root Parasite

Partial Stem Parasites

Definition:

Those partial parasites whose haustoria penetrate in the stem of the host and

suck their nutrition from vascular tissues of stem are called Partial Stem

Parasite.

Explanation

Loranthus, is a partial stem parasite. It has thick green leaves, a woody stem and

elaborated haustorial system. It can manufacture some of its food with the help

of nutrients and water absorbed from host plants. The seeds get stuck upto the

stem of host plant and germinates sending its haustoria in the tissues of the host.

Examples

Loranthus -> found on shrubs, roseaceous tree, Bauhinia and mango

Viscum -> produce haustorial branches for an internal suckling system.

Cassytha Filliformis -> found in tropics

Partial Root Parasites

Example:The examples of this category are rare.

One important example is

* Sandle Wood Tree

Saprophytes

Definition

“Those plants which depend for their nutrition on dead or rotten organic

remains of plants or animals are called as Saprophytes”

or

“Plants which break up complex dead food material into simple compounds and

use them for their growth and development are called as Saprophytes.”

Types Of Saprophytes

Saprophytes can be divided into two types:

1. Total Saprophytes

2. Partial Saprophytes

1. Total Saprophytes

Definition:



“Those plants which depend entirely for their nutrition on dead organic matter

are called Total Saprophytes.

2. Partial Saprophytes

Definition:

“Those plants which depend partially on dead organic matter are called Partial

Saprophytes.”

Examples Of Saprophytes

There are some examples of Saprophytes among flowering plants.

1. Neothia (bird’s net or orchid)

2. Monotrapa (Indian Pipe)

In both of these cases, the roots of plant form a Mycorhizzal Association with

fungal mycelium to help in absorption process.

Special Mode Of Nutrition

Carnivorous Or Insectivorous Plants

Definition:

“The plants which have as their prey, insects and small birds are called

Carnivorous plants. It is a special mode of nutrition in partially autotrophic and

partially heterotrophic plants."

Explanation

Partially autotrophic and partially heterotrophic plants are carnivorous, which

possess the green pigments and can manufacture CHO but are not capable of

synthesizing nitrogenous compounds and proteins. For their nitrogen

requirement, carnivorous plants have to depend on insects, which they catch and

digest by specific devices developed in them. J.D. Hooker suggested that the

digestion of carnivorous plants is like that of animals.

Common Areas Where These Plants Grow

These plants commonly grow in areas where nitrogen is deficient due to

unfavourable atmosphere for nitrifying bacteria but favourable atmosphere for

denitrifying bacteria.

Some Common Examples

1. Pitcher Plant

In Pitcher plant leaf is modified into pitcher like structure which is insect

trapping organ.

Examples

Common examples are:



• Nepenthes

• Sarracenia

• Cephalotus

• Neliamphora

• Darling tonia

2. Dorsera Intermedia Or Sundew

This plant has half a dozen prostrate radiating leaves, which bear hair like

tentacles each with gland at its tip. The insects attracted by plant odour are

digested.

3. Dionaea Muscipula Or Venous Fly Trap

Most well-known of all carnivorous plants. It has a resette of prostrate radiating

leaves with inflorescence in the centre. The petiole of leaf is winged and lamina

has two halves, with mid-rib in the centre. Each half has 12-20 teeth. In the

centre of dorsal surface of lamina are numerous secretory glands, three hairs

projecting out, which are sensitive to touch.

4.Aldrovanda (Water Fly Trap)

It is a root less aquatic plant with floating stem. It has ressettes of modified

leaves, which have two lobed mobile lamina having teeth at the margin and

sensitive jointed hairs and glands on the surface.

5. Utricularia Or Bladder Wort

It is a root less plant having branched slender stem. Leaves are also much

divided and some leaflets are modified into bladder like traps of about 1/16 to

1/8 inches in diameter.

Human Digestive System

Digestion:

“It is the process by which large complex insoluble organic food substances are

broken down into smaller simpler soluble molecules by the help of enzymes”.

Digestion in man is mechanical (break down) as well as chemical (enzymatic

hydrolysis).

Nutrition

Heterotrophic, i.e. man is dependent upon ready made food.

Type Of Digestion

Extracellular, i.e. digestion takes place outside the cells but within GIT.



Type Of Digestive System

Tube Like Digestive System, i.e,

• Digestive cavity is separated from body cavity.

• It has both openings, mouth and anus.

• “Complete” digestive sytem

This one-way tube is known as Gastro-Intestinal Tract (GIT)

Organs Of Gastro-Intestinal System

The adult digestive system is a tube approximately 4.5m (15ft) long and

comprises of

(A) G I T

1. Mouth

2. Oral Cavity -> Teeth, Tongue

3. Pharynx

4. Oesophagus

5. Stomach

6. Small Intestine -> Duodenum, Jejunum, Ileum

7. Large Intestine -> Caecum, Rectum, Colon

8. Anus -> Parotid

(B) Associated Glands

1. Salivary Glands -> Sublingual, Submandibular

2. Liver

3. Pancreas

(1) Mouth

The anterior or proximal opening of gut, which is bounded anteriorly by lips. It

opens into oral cavity.

Function

1. Lips close the mouth.

2. Lips also help in ingestion.

(2) Oral Cavity

It is a wide cavity supported by bones of skull

Boundaries

• Cheeks form side walls.

• Tongue forms floor

• Palate forms roof



• Jaws form roof boundary of mouth.

+ Jaws

Upper jaw is fixed while lower jaw is moveable. Both jaws bear teeth.

Content Of Cavity

Teeth and Tongue

+ Teeth

“The hard-calcified structures, meant for mastication (chewing)”

Number Of Sets

Humans have 2 sets of teeth ® DIPHYODONT

(1) Deciduous

The 20 teeth of first dentition, which are shed and replaced by permanent teeth.

(2) Permemant

The 32 teeth of second dentition, which begin to appear in human at about 6

year of age. It consisting of 8 incisors, 4 canines, 8 premolars and 12 molars.

+ Molars are absent in deciduous set.

Heterdont They are embedded in gums -> Thecodont

Structure Of A Tooth

Each tooth consists of 3 parts

1. Crown

2. Neck

3. Root

Functions

1. Incisors are cutting and biting teeth. Their flat sharp edges cut food into

smaller pieces.

2. Canines are pointed teeth and poorly developed in humans. They are used in

tearing, killing and piercing the prey.

3. Premolars and Molars are grinders and used for crushing the food.

4. Mastication increases surface are of food for action of enzymes.



5. If one attempt to swallow a food particle too large to enter ocsophagus, it may

block the trachea and may stop ventilation.

“Dental Diseases”

Plaque

“A mixture of bacteria and salivary materials”

OR

“A soft thin film of food debris, mucin and dead epithelial cells deposited on

teeth, providing medium for growth of bacterias”

* Plague plays an important role in development of dental caries, periodontal

and gingival disease. Calcified plaque forms dental calculus.

Periodontal Diseases

Accumulation of plaque causes inflammation of gums. Continuous

inflammation may spread to the root of tooth and destroy peridental layer.

Eventually tooth becomes loose and falls off or may have to be extracted.

Dental Calculus

Plaque combine with certain chemicals in saliva which become harden and

calcified forming deposits of calculus which cannot be removed by brushing.

Dental Caries

When bacteria of plaque convert sugar of food into acid, the enamel (hardest

substance of body, covers dentin of crown of teeth) is dissolved slowly. When

dentine and pulp are attached, produce toothache and loss of teeth.

Factor Causing Dental Caries

• Prolonged exposure to sugary food stuff.

• Disturbance of saliva composition

• Lack of oral hygiene

• Low levels of fluoride in drinking H2O

Prevention

Add ‘flouride’ in drinking H2O or milk

Take ‘flouride’ tablet

Use ‘flouride’ tooth paste.

Tongue

Tongue is a muscular fleshy structure forming floor of oral cavity. Tongue has

• a root

• a tip and



• a body

It is attached posteriorly and free anteriorly

Taste Buds

Taste buds respond to sweet, salt, acid and bitter taste, only when these

substances are dissolved in H2O of saliva.

Taste buds are most numerous on sides of vallate papillae. They are absent on

mid dorsal region of oral part of tongue.

Tongue Papillae

Papillae are projections of mucous membrane which gives characteristic

roughness to the tongue. These are of 3 types

• Vallate Papillae

• Fungiform Papillae

• Filliform Papillae

Functions

1. Its function is ‘Spoon-like’.

2. It mixes the masticated food with saliva

3. It helps in swalloing

4. It helps in sucking and testing food.

Salivary Glands

3 pairs of salivary glands.

(1) Parotid

Lies at base of pinnae.

It is supplied by IX cranial nerve.

(2) Sub Lingual

• Lies at base of tongue.

• Supplied by VII cranial nerve.

(3) Sub Mandibular

• Lies at base of lower jaw.

• Supplied by VII cranial nerve

Function

These three pairs produce about 1.5dm3 of saliva each day.



These glands are supplied by Parasympathetic Nervous System. Fibers of

parasympathic N.S lie in Cranial nerves. These nerves increase their secretion.

Saliva

It is a watery secretion containing 95% H2O, some mucous, amylase and

Lysozyme enzyme.

• Salivation is brought about by “Parasympathetic Nervous System.”

• Saliva is secreted in response to the sight, thought, taste or smell of food.

Functions

1. Mucous of Saliva moistens and lubricates the food particles prior to

swallowing.

2. Salivary Amylase or Ptylin begins digestion of starch, first to dextrins and

then to maltose (dissacharide).

3. Lysozyme destroys the oral cavity pathogen bacteria. It has a cleansing

action.

4. Water in Saliva, dissolve some of the molecules in food particle then they

react with chemo receptors in taste buds, giving sensation of taste, hence, the

H2O enables taste buds to respond.

5. Saliva is fully saturated with calcium and this prevents decalcification of

teeth.

6. Saliva makes speech possible by moistening the mouth; it is not possible to

talk if the mouth is dry.

7. It acts as a lubricant and enables a bolus (a rounded mass of semi-solid,

partially digested food particles stick together by mucus) to be formed. The

tongue pushes bolus into pharynx.

3. Pharynx

The musculo-membranous passage between mouth and posterior nares and the

larynx and oesophagus.

Openings

It contains opening of oesophagus, glottis, Eustachian tube and internal nostrils.

Parts Of Pharynx

Nasopharynnx



The part above the level of soft palate is Nasopharynx, which communicates

with auditory tube.

Oropharynx

It lies between soft palate and upper edge of the epiglottis.

Hypopharynx

It lies below the upper edge of epiglottis and opens into larynx and oesophagus.

Function -> Swallowing

Swallowing in its initial stages is voluntary but involuntary afterwards.

Mechanism

1. As the bolus of food moves into the pharynx, the soft palate is elevated and

lodges against the back wall of pharynx sealing the nasal cavity and preventing

food from entering it.

2. The swallowing center inhibit respiration, raises the larynx and closes the

glottis (opening between vocal cords), keeping food from getting into trachea.

3. As the tongue forces the food further back into the pharynx, the bolus tilts the

epiglottis backward to cover the closed glottis.

4. This pharyngeal act of swallowing lasts about 1 second.

4. Oesophagus

This is a narrow muscular tube of about 25cm long. It connects pharynx to

stomach. It passes through the thoracic cavity and penetrates the diaphragm,

then it joins the stomach a few cms below the diaphragm.

Muscles Of Oesophagus

• Upper-one third is surrounded by skeletal muscles.

• Lower two-third is surrounded by smooth muscles.

Sphincters (Muscular Valves)

1. Skeletal muscles, just below pharynx surrounding oesophagus form Upper

Oesophageal Sphincter.

2. Smooth muscles in last 4 cm of oesophagus forms Lower Oesophageal

Sphincter. It seals the exit of food.

Function

It conveys the food or fluid by Peristalsis.

Peristalsis



Alternate rhythmic contraction and relaxation waves in the muscle layers

surrounding a tube are called Peristaltic Waves.

It is the basic propulsive movement of GIT.

Stimulus

Distention of oesophagus.

Timing

An oesophageal peristaltic wave takes about ‘9 sec’ to reach stomach. Bolus is

moved toward stomach by progressive peristaltic wave which compresses the

lumen and forces the bolus ahead of it.

Anti-Peristalsis

Peristalsis in opposite direction, i.e. from stomach towards pharynx.

Stimulus

• Early stages of GIT irritation.

• Over distention.

Vomiting

Anti peristalsis begins to occur, some minute before vomiting appears. The

initial events of anti peristalsis may occur repeatedly without vomiting, called

Retching. 1. Vomiting begins with a deep inspiration, closure of glottis and

elevation of soft palate.

2. Abdominal and thoracic muscles contract, raising intradominal pressure.

3. Stomach is squeezed, lower oesophageal sphincter relaxes allowing expulsion

of stomach content into oesophagus in form of Vomitus.

5 Oesophagus

Stomach is a hollow, muscular, distensible bag like organ.

Location

Lying below the diaphragm on the left side of abdominal cavity.

Structure

It has 3 regions.

1 Cardiac Region



This is the anterior region which joins the oesophagus through a cardiac

sphincter. It has muscous glands which helps in lubrication of food.

2 Body

The middle portion is body of stomach. The part to the left and above the

entrance of oesophagus is called Fundus of stomach. Body of stomach contain

gastric glands. Gastric glands contain 3 types of cells.

Mucous Cells

• These cells are present at opening of gastric glands and secrete mucous.

• It lubricates the food and passage.

• It also protects the epithelium from self-digestion by pepsin.

Oxyntic / Parietal Cells

• They lie deeper within the glands and secrete dilute HCl having a pH of

1.5 – 2.5.

• Kills microbes

• Solublization of food particles.

• Activate the inactive enzyme pepsinogen into Pepsin.

Chief Cell / Zymogen Cells

• Deeper in the glands and secrete enzyme precursor Pepsinogen.

• After converting into Pepsin, it acts upon proteins and convert them into

short chain polypeptides, Peptones.

The collective secretion of the above mentioned 3 cells is called as GASTRIC

JUICE.

Pyloric Region

The posterior region is the terminal narrow pyloric region or Antrum. It opens

into duodenum through pyloric sphincter / pylorus.

Its Secretion -> Gastrin

This region does not secrete acid. It secretes mucous, pepsinogen and a

hormone GASTRIN. Endocrine cells which secrete GASTRIN are scattered

throughout epithelium of antrum.

Stimulus

Partially digested proteins.

Action

Activate gastric glands to produce gastric juices.



“Renin”-Additional Enzyme In Infant

In infants, Renin is secreted which curdles the milk.

Function Of Stomach

(1) Storage Of Food

Pylorus acts as a valve and retain food in the stomach for about 4 hours.

Periodic relaxation of pylorus releases small quantities of chyme into

duodenum.

(2) Mechanical Digestion

The weak peristaltic waves also called mixing waves move along the stomach

wall once every 20 seconds. These waves not only mix the food with secretions

but also move mixed contents forward.

(3) Chemical Digestion

Gastric juice converts food to a creamy paste called CHYME.

6. Small Intestine

The small intestine is a coiled tube approximately 6 meters long and 2.5 cm

wide, leading from stomach to large intestine. It fills most of the abdominal

cavity.

Divisions

There are 3 divisions.

A. Duodenum

It begins after pyloric stomach and ends at jejunum. Its length is about 30cm.

Secretion

Pancreatic juice from pancreas by pancreatic duet and bile from gall bladder by

common bile duct act on chyme from stomach. Both ducts open via a common

opening in duodenum.

Bile

Synthesis, Storage And Secretion

Bile is made in liver and enters the duodenum via the bile duct. It stores in gall

bladder.

Colour



Bile is yellow in colour but changes to green due to exposure to air.

Constituent

• Water.

• Bile Salts

+ Bile Salts

These are sodium salts of compounds of cholestrol. NaHCO3 is also present

which neutralizes the acidity of gastric juice and make the chyme alkaline.

The main bile salts are for emulsification of fats.

Emulsification Break down of large fat particles into small droplets so that they

can mix well with H2O to form emulsions.

+ Bile Pigments

BILIRUBIN and BILIVERDIN are excretory products formed by breakdown of

haemaglobin of worn out RBCs in the liver.

Action Of ‘Cholecystokinin (Cck)’ CCK is a hormone and produced by cells of small intestine.

Stimuli For Hormone Release

Fatty food in duodenum.

Action

CCK is released in blood and reaches to gall bladder and causes it to contract.

Due to contraction of gall bladder, bile enters the duodenum.

‘Pancreatic Juice’

Pancreatic juice is produced in pancreas by its exocrine function and secreted

via pancreatic duct. It is a colourless fluid.

Action Of Secretin

Secretion is also a hormone and produced by cells of small intestine.

Stimuli

Acid (HCl) carried with chyme in small intestine.

Action

It increases the secretion of pancreatic juice and also increases bicarbonate

secretion in bile.

Constituents

(1) Trypsin (Protease)



It is secreted in an inactive form called Trypsinogen which is activated by action

of an enzyme produced by duodenum called enterokinase.

Action

Break proteins and long chain polypeptides into small peptide fragments.

(2) Chymotrypsin (Protease)

It is also secreted in inactive form, Chymotrypsinogen which is converted into

chymotrypsin by action of Trypsin.

Action

Converts casein (milk proteins) into short chain peptide.

(3) Amylase

It is similar to salivary amylase. It acts on polysaccharides (Glycogen and

Starch) and convert them into maltose (a disaccharide).

(4) Lipase

It acts on emulsified fat droplets. It splits off lipid into fatty acid and glycerol,

hance the digestion of fat is completed in duodenum.

(B) Jejunum

It extends from duodenum to illeum. It is 2.4 meters long. Here the digestion of

food is completed.

Collection Of Peptidases, Erepsin

Peptidases complete the breakdown of polypeptide into amino acids.

Nucleotidase

It converts nucleotides into nucleoside. End products of digestion, i.e,

monosaccharide and A.As are liberated in lumen of small intestine for

absorption in ileum.

(C) Ileum

It is the last and longest part of small intestine. Its length is about 3.6 meters

long. It contains digested food in true solution form.

Structure

The inner wall (Mucosa and Submucosa) of small intestine is thrown into

various folds. These folds have finger-like microscopic projections called villi.

Villi

Each villus is lined with epithelial cells having microvilli on their free surfaces.



Their walls are richly supplied with blood vessels and lymph vessels called

Lacteals. Some smooth muscles are also present in villi.

Mechanism Of Absorption

Major function of ileum is absorption of digested food, which is facilitated by

highly folded inner wall of intestine with villi on their surfaces.

This increases the absorptive area. Villi are able to move back and forth due to

muscle fibers in them.

• The monosaccharide and A.As are absorbed into blood capillaries by

Diffusion or Active Transport.

• Fatty acid and glycerol enter epithelial cells of villi, covert into

triglycerols and enters Lacteals and pass into blood stream.

Blood Drainage Of Intestine

All capillaries converge to form hepatic portal vein, which delivers absorbed

nutrients to liver.

7. Large Intestine

Small intestine opens into large intestine, which is a large diameter tube about

6.5 cm. It is not coiled by relatively has 3 straight segments.

+ Caecum

+ Colon

+ Rectum

+ CAECUM

Caecum is a blind ended pouch placed in the lower right side of abdominal

cavity. It gives a 10cm long finger like projection, Appendix. Appendix is a

vestigial organ, i.e. an organ present in rudimentary form and has no function

but has well developed function in ancestors.

Function

Symbiotic bacteria, present in caecum, help in digestion of cellulose, which is

not digested by man, as enzyme for digestion is absent.

+ Colon

Colon is longest part and has 3 regions:

+ Ascending colon

+ Transverse Colon

+ Descending Colon

-> SIGMOID COLON is terminal part of Descending Colon.



Function

Inorganic salts, water and mineral absorbed in colon. Some metabolic waste

products and excess calcium of body as salts are excreted into large intestine.

Each day 500 ml of intestinal content enter the colon and during its passage the

amount reduced to 150 ml due to absorption of H2O.

+ Rectum

Rectum is last portion, it stores faeces for some time.

When the faeces enter into rectum, it brings about a desire for defecation. The

process by which faeces passes out is called Egestion.

Symbiotic Bacteria

Many symbiotic bacteria in large intestine provide the body with a source of

vitamin and A.As, especially vitamin B complex and K, which are absorbed in

blood stream. Administration of Broad-spectrum antibiotics destroys these

bacteria and a vitamin deficiency results, which is then make up by vitamin

intakes.

8. Anus

External opening of digestive system is ANUS.

Sphincters

Two sphincters surround the anus:

+ Internal Sphinter -> made up of smooth muscle and under Autonomic control

(involuntary control).

+ Outer Sphincter -> made up of skeletal muscle and under Somatic Control

(voluntary control).

Faecus

Faecus consists of:

Dead bacteria, cellulose, Plant fibers, dead mucosal cells, mucous, cholesterol,

bile pigment derivatives and H2O.

9. Liver

Liver is the largest organ and gland of body. It weighs about 1.5 kg. It is also

called ‘HEPAR’.

Colour

It is reddish brown in colour.



Location

It lies below the diaphragm on right side.

Lobes Of Liver

Liver has 2 lobes, i.e. Right and Left. Left is further divided into two lobes.

Functions Of Liver

‘As A Metabolic Factory’

It maintains the appropriate level of nutrients in blood and body. It is performed

in 3 ways.

A. Glucose Metabolism

1. Additional (Surplus) Glucose is converted into Glycogen by action of

INSULIN after every meal. This is called Glycogenesis.

2. Glycogen is splitted into Glucose for body needs. This is called

Glycogenolysis.

3. New glucose for body requirement is formed by non-carbohydrate

compounds. This is called Gluconeogenesis.

B. A.As Metabolism

A.As are also stored after deamination (removal of NH2 group), which forms

Urea.

C. Fatty Acid Metabolism

It also processes F.As and stores the products as Ketone Bodies, which are

released as nutrients for active muscles.

‘As A Detoxification Center’

Poisons and toxic substances, which can harm the body, are degraded into

harmless compounds. It excretes out bile pigments and waste products.

‘As A Storage Organ’

It stores vitamins and also produces proteins and coagulating factors of blood.

Gall Blader

It lies on undersurface of liver, a pear-shaped organ.

Function

It concentrates and stores the bile secreted by liver.

Biliary Tracft



Two hepatic ducts from liver bring bile and join the cystic duct from gall

bladder. This form common bile duct, which joins Pancreatic duct coming from

pancreas bringing pancreatic juice. These 2 ducts open into duodenum at same

opening.

10.Pancreas

A large elongated gland situated transversely behind the stomach, between

spleen and duodenum.

Parts Of Pancreas

Head

It is the right extremity and directed downwards.

Tail

Left extremity is transverse and terminates close to spleen.

Body

The main portion in middle.

Duct

Pancreatic duct opens into duodenum with common bile duct and delivers

pancreatic juices.

Working As A Gland

It works both as an endocrine and exocrine gland.

Endocrine Pancreas

Endocrine part consists of Islets Of Langerhans.

The islets contain.

α cell (Alpha)

Produce Glucagon which increases blood glucose level.

β cell (Beta)

Produce Insulin which reduces blood glucose level.

Δ cell (Delta)

Produce Somatostatin (SS) which inhibit the release of many harmones.

P P cells

Secrete pancreatic polypeptide.

Exocrine Pancrease



The exocrine part consists of pancreatic acini. Acini are secretory unit that

produce and secrete pancreatic juice into duodenum which contain enzymes

essential to digestion.

Disorders Of ‘Git’

(1) Diarrhoea

Abnormal frequency and liquidity of fecal discharges. It is the rapid movement

of fecal matter through large intestine.

Causes

Entritis

It may be caused by infection of intestinal wall (mucosa) by a virus or bacteria.

Due to infection, mucosa becomes irritated and motility of intestinal wall

increases.

Cholera

Cholera is a bacterial disease caused by Vibrio Cholera. It can cause diarrhoea.

It causes extreme amount of HCO3- (bicarbonates ion) and Na and H2O to be

secreted in faeces. It may cause death.

Psycogenic Diarrhoea

It is caused by nervous tension. In the young and elderly, diarrhoea may lead to

a serious depletion of H2O and inorganic salts.

(2) Dysentary

Acute inflammation of intestines especially of the colon.

Symptoms

Pain in abdomen, tenesmus (straining), frequent stool containing blood and

mucus.

Causes

• Protozoa. (like amoebic dysentery)

• Parasitic Worms.

• Bacteria. (like bacillary dysentery)

• Chemical Irritants.

(3) Constipation

Infrequent or difficult evacuation of faeces. OR Slow movement of faeces

through large intestine.

Faeces becomes hard due to long time available for H2O absorption.

Cause



Irregular bowel habits that have developed through a life time of inhibition of

normal defection reflaxes.

Treatment

* Laxatives are used

* Substance which hold H2O with them

(4) Piles

Also, called Haemorrhoids Varicose dialatation of veins occurring in relation to

anus, resulting from a persistence increase in pressure.

External Piles

Venous dialatation covered with modified anal skin.

Internal Piles

Dilatation of veins covered by mucous membrane.

Cause

Constipation

The pressure exerted to defecate stretches skin with vein and causes dilation.

Prevention

Can be avoided by regular habit of defecation and by use of fiber diet.

(5) Dyspepsia

Impairment of the power or function of digestion, usually applied to epigastria

discomfort following meals.

Cause

May be due to peptic ulcer.

Symptoms

• Heart burn.

• Flatulence (distended with gas)

• Anorexia, nausea, vomiting with or without abdominal pair.

Functional / Non-Ulcer Dyspepsia

Dyspepsia in which symptoms resemble those of peptic ulcer, although no ulcer

is detectable. It is caused by disturbance in moter function of alimentary tract.

(6) Peptic Ulcer



Since pepsin, is a protein digesting enzyme, it may digest the stomach wall, the

first part of duodenum or rarely lower part of oesophagus where stomach juices

frequently refluxes. This condition is called Peptic Ulcers.

Gastric Ulcers

Duodenal Ulcers

Causes

• Excessive secretion of acid and pepsin.

• It may be hereditary.

• Psychogenic factors.

Complications

Complications of peptic ulcers are perforation, haemorrhage and obstruction.

Investigations

1. Acid output of stomach is studied.

2. Ulcers cavity may be shown up on X-rays after ingestion of insoluble barium

sulphate (Barium meal).

3. It may be seen using optical instrument passed down through oesophagus

(endoscopy)

(7) Food Poisoning

Also, called GASTRO-ENTRITIS

Causes

Infection

By bacteria, virus, protozoa. ‘Salmonella’ species are very common.

Non-Infectious

Allergy, irritating food or drink.

Symptoms

Vomiting and diarrhoea within 48 hours.

(8) Mal Nutrition

Any disorder of nutrition due to unbalanced diet or due to defective assimilation

or utilization of foods.

An organism may be deficient or may receive excess of one or more nutrients

for a long period of time.



Under Nutrition

Deficiency is known as under-nutrition. It is most common problem of under

developed countries.

Over Nutrition

Excess is known as over-nutrition. Obesity with heart problems and reduced life

expactency are its symptoms and are more common in developed countries.

(9) Obesity And Over Weight

Increase in body weight beyond the limitation of skeletal and physical need as

the result of accumulation (excessive) of fat in the body.

It is the most common nutritional disorder. It is most prevalent in middle age. It

may be hereditary or family tendency over weight results in rate of mortality.

(10) Anorexia Nervosa

Loss or lack of appetite for food is called Anorexia.

Anorexia Nervosa

An eating disorder affecting young females, characterized by refusal to maintain

a normal minimal body weight, intence fear of gaining body weight, intense fear

of gaining weight or becoming obese. Sometimes accompanied by spontaneous

or induced vomiting.

(11) Bulimia Nervosa

Exclusively found in women and the age of onset is slightly older than for

anorexia.

Recurrent episodes (bouts) of binge (uncontrolled) eating. Lack of self-control

over eating during binges.

Attacks occur twice a week and involve rich foods such as cakes and chocolates

and dairy products.

Digestive System of Cockroach

Cockroach belongs to Phylum: Arthropoda Class: Insecta / Hexapoda

Nutrition

Omnivorous, i.e. It can eat any kind of organic matter. They search their food

by antennae.

Type Of Digestive System



Tabular Digestive System, i.e. straight slightly coiled dig tube, open at both

ends, complete dig. system.

Organs Of Digestive System

+ Alimentary Canal

It is divisible into 3 parts

1. Fore Gut / Stomodaeum

• Mouth

• Buccal Cavity

• Oesophagus

• Crop

• Gizzard

2. Midgut / Mesenteron / Ventriculus

• Hepatic Caeca

3. Hind Gut / Proctodaeum

• Ileum

• Colon

• Rectum

• Anus

+ Associated Gland

Salivary Glands

1.Fore Gut

Mouth

It lies at base of pre-oval cavity which is bounded by mouth part.

Labrum / Upper Lip

Appendage of 3rd head segment.

Mandibles

Appendage of 4th head segment. They help in mastication

Maxillae

Appendages of 5th head segment. They pick up and bring food.

Labium / Lower Lip

Appendages of 6th head segment.

Buccal Cavity



The mouth opens into buccal cavity which is short and receives the common

duct of salivary glands.

Saliva cantain ‘Amylase’ which act upon carbohydrates.

Oesophagus

Buccal cavity opens into pharynx which in turn opens into oesophagus which is

a long and thin tube lying in thorax.

Crop

It is a large thin walled and pear shaped structure meant for storing food.

Gizzard

Crop opens into thick walled, rounded gizzard with muscular chitins lining

which is internally produced six teeth for grinding and straining the food.

2. Mid-Gut

It is narrow, short and tubular portion originate from gizzard. At beginning it

receives eight hepatic caeca hanging in haemocoel (body cavity filled with

white colour blood), ending blindly but opening in gut.

Enzymes From Hepatic Caeca

They are lined by glandular cells, which secrete enzymes.

Enzymes from hepatic caeca and mid-gut flow back into crop where digestion

takes place.

Enzymes

1. Pedtidases And Trypsin Like Enzyme -> digest proteins.

2. Amylases -> complete digestion of starches

3. Lipase -> digestion of fats.

Digested food form a bolus and enclosed in a thin chitinous tube secreted by

stomodael valve of gizzard. This covering is called Peritrophic.

Membrane

It is permeable to enzymes and digested food. This membrane protects the

lining of mid gut from damage by hard indigestible components of food.

Digested food is absorbed in mid gut.

3. Hind-Gut

It has a cuticular ectodermal lining.

Ileum



Short, narrow and muscular ileum. The beginning of ileum is marked by 60-70

fine and long, greenish yellow Malphigian Tubules. (excretory in function)

Colon

Colon is long, wider and coiled portion of hind gut

Rectum

Rectum is broad last part of hind gut. It absorbs H2O and conserves the much-

needed H2O from undigested food before expelling out the faeces.

Anus

Anus is the last opening of digestive system by which hind gut opens to outside.

Salivary Glands

Salivary glands are 2 in number. each present on the sides of oesophagus. Saliva

contain amylase for digestion of carbohydrates.

CHAPTER 13

GASEOUS EXCHANGE

Respiratory Organs Of Cockroach Tracheal System

Cockroach has evolved a special type of invaginated respiratory system called

Tracheal system, especially adopted for terrestrial mode of life and high

metabolic rate of insects.

Structural Constituents Of Tracheal System

1. Trachea

2. Spiracles

3. Tracheoles

1.Trachea

Tracheal system consists of number of internal tube called Trachea which are

the connection between the spiracles and tracheal fluid.

2. Spiracles

Laterally, trachea open outside the body through minute, slit like pores called as

spiracles.

• There are 2 pairs of spiracles on lateral side of cockroach.

• 2 lie in thoracic segments and 8 in first abdominal segments.

3. Tracheoles



On the other side, trachea ramify throughout the body into fine branches or

tracheols.

• Tracheoles, finally end as blind, fluid filled fine branches which are

attached with cells of tissue.

• Both the trachea and tracheoles are lined internally by thin layer of cuticle.

Mechanism Of Respiration “Inflow Of Oxygen”

The cockroach takes in air directly from the atmosphere into the trachea through

spiracles. This air diffuses directly into fluid filled tracheoles through which

diffuses into the cells of tissues. Hence the blood vascular system of cockroach

is devoid of haemoglobin.

Outflow Of Carbondioxide

Removal of CO2 from cells of body is largely depended upon plasma of blood,

which takes up CO2 for its ultimate removal through body surface via the

cuticle.

Respiratory System Of Fish

Main Respiratory Organ

In fish, main respiratory organs are “Gills”. They are out growth of pharynx and

lie internally with in the body so that they are protected from mechanical

injuries.

Internal Structure Of Gills

Each gill is highly vascularized structure. It is composed of

1. Filaments

2. Gill bar or Gill arch

3. Lamella

1. Filaments

Each gill is composed of two rows of hundreds of filaments, which are arranged

in V-shape.

2. Gill Bar Or Gill Arch

Filaments are supported by a cartilage or a long curved bone the gill bar or gill

arch.

3. Lamella

Lamella is a plate like structure which is formed by infolding of filaments.

Lamella greatly increase the surface area of the gill. Each lamella is provided by

a dense network of capillaries.



Operculum (In Bony Fishes)

Gills are covered on each side by gill cover called “operculum”

Mechanism Of Ventilation

In bony fishes, ventilation is brought about by combined effect of mouth and

operculum.

• Water is drawn into the mouth. It passes over the gills through pharynx and

ultimately exists at the back of operculum through open operculur valve.

• Water is moved over the gills in a continuous unidirectional flow by

maintaining a lower pressure in operculur cavity than in buccopharynx

cavity.

Counter Current Flow Of Water And Blood

• Gaseous exchange is facilitated in gills due to counter current flow of H2O

and blood.

• In the capillaries of each lamella, blood flows in direction opposite to the

movement of water across the gill. Thus, the most highly oxygenated blood

is brought to water that is just entering the gills and has even high O2

content than the blood. As the H2O flows over the gills, gradually losing its

oxygen to the blood, it encounters the blood that is also increasingly low in

oxygen. In this way, a gradient is establishment which encourages the

oxygen to move from water to blood

Importance

Counter current flow is very effective as it enables the fish to extract upto 80–

90% of the oxygen from water that flows over the gills.

Respiratory System Of Man

Main Function Of Respiration

The main function of respiratory system is inflow of O2 from the atmosphere to

the body and removal of CO2 from body to the atmosphere.

Components Of Respiratory System

(1) Paired Lungs

The respiratory (gas exchange) organs.

(2) Air Passage Ways

Which conduct the air

(3) Thoracic Cavity

Which lodges the lungs



(4) Intercostal Muscles And Diaphragm

Which decreases and increase the diameters of thoracic cavity

(5) Respiratory Control Centres

Areas in brain which control the respiration.

Details Of Components

+ Thoracic Cavity

Paired lungs with in the pleural sacs are situated in the thoracic cavity.

Separating the thoracic cavity from the abdominal cavity is a dome-shaped

musculo-tendinuous partition called as Diaphragm.

Boundaries Of Cavity

Thoracic cavity is supported by bony cage (thoracic cage) which is made up of

• Sternum -> in front

• Vertebral column -> at the back

• 12 pairs of ribs -> on each side

• Ribs are supported by Intercostal muscles

Function

Increase in thoracic cavity diameter is responsible for inspiration. While

decrease in diameter is responsible for expiration.

Air Passage Ways

Air is drawn into the lungs by inter-connected system of branching ducts called

as “Respiratory tract” or “Respiratory passage ways” Air passage ways consists

of

Air Conducting Zone(which only conducts the air)

1. Nostrils

2. Nasal Cavity

3. Pharynx (nasopharynx and oropharynx)

4. Larynx

5. Trachea

6. Bronchi

7. Bronchioles (also called terminal Branchioles)

Respiratory Zone (Where gaseous exchange takes place)

8. Respiratory Bronchioles

9. Alveolar duct



10. Alveolar sacs or alveoli

General Functions Of Conducting Air Passages

1. Conduction of air from atmosphere to the lungs

2. Humidification of inhaled dry air.

3. Warming / cooling of air to body temp.

4. The injurious particles are entrapped by mucous and removed by ciliary

movements.

5. Lymphoid tissues of pharynx provide immunological functions

6. Cartilages prevent the passages from collapse but are not present in

Bronchioles which remains expanded by same pressure that expand the alveoli.

Conducting Zone

1. Nasal Cavity

Atmospheric air enters the respiratory tract through a pair of openings called

external nares (Nostrils), which lead separately into nasal cavity. Nasal cavity

opens into naso pharynx through posterior nares (choanae).

• Nasal cavity is lined internally by Pseudostratified columnar ciliated

epithelium containing mucous secreting cells.

• Hairs, sweat and sebaceous glands are also present.

Specialized Functions

• Warming of air

• Humidification or moistening of air

• Filteration of air with the help of hairs

• All these together called as Air conditioning function of upper respiratory

passages

• Olfaction ( sense of smell)

2. Pharynx

Air enters from Nasal cavity into pharynx through internal nostrils. The

openings of nostrils are guarded by soft palate. It is internally lined by

Pseudostratified ciliated epithelium, mucous glands are also present.

Function

Pharynx is responsible for conduction of air as well as food

3. Larynx (Voice Box)



Pharynx leads air into larynx through an opening called glottis. Glottis is

guarded by flap of tissue called epiglottis. During swallowing, soft palate and

epiglottis close the nostrils opening and glottis respectively so that food is

prevented to go either into nasal cavity or glottis. Larynx, a small chamber

consists of pair of vocal cords.

Function

During speech, vocal cords move medially and their vibration produce sound

4. Trachea (Wind Pipe)

Larynx leads the air into a flexible air duct or trachea. It bears C-shaped tracheal

cartilages which keep its lumen patent during inspiration. Its internal lining is

pseudostratified columnar ciliated epithelium containing mucous secreting

goblet cells.

Function

• Conduction of air

• Due to mucous and upward beating of cilia, any residues of dust and germs

are pushed outside the trachea towards the pharynx.

5. Bronchi

“At its lower end, trachea bifurcates into two smaller branches called Principle

Bronchi↑ which leads the air into lung of its side. They are also supported by C-

shaped cartilage rings upto the point where they enter the lungs”.

• In all areas of trachea and bronchi, not occupied by cartilage plates, the

walls are composed mainly of smooth muscles.

6. Bronchioles

On entering the lungs, each bronchus divide repeatidly. As the bronchi become

smaller, U-shaped bars of cartilage are replaced by irregular plates of cartilages.

The smallest bronchi divide and give rise to Bronchioles (less than 1.5 mm in

diameter).

7. Terminal Bronchioles

Bronchioles divide and give rise to terminal bronchioles (less than 1 mm in

diameter). Walls possess no cartilages and are almost entirely the smooth

muscles. These are the smalled airways without alveoli.

Respiratory Zone

In this zone of respiratory tract, gaseous exchange between capillary blood and

air takes place.



1. Respiratory Bronchioles

Terminal bronchioles show delicate outpouchings from their walls, which

explains the name Respiratory Bronchioles (less than 0.5 mm in diameter). They

bear the pulmonary alveoli.

2. Alveolar Ducts and Sacs

Each respiratory bronchioles terminates at a tiny hollow sac like alveolar duct

that lead into tabular passages with numerous thin walled out pouchings called

Alveolar sacs.

3. Pulmonary Alveoli

The alveolar sacs consist of several alveoli openings into a single chamber.

Alveoli are the site of exchange of respiratory gases so they are considered as

Respiratory surfaces of lungs. Each alveolus is surrounded by a network of

blood capillaries.

Internal Structure Of Alveoli

The alveolar lining cells consists of

1. Type I cells

2. Type II cells

They are also called pneumocytes.

“Bifurcation of trachea is called Carina”.

Type I Pneumocytes

Squamous shaped cells which form the epithelial lining of alveoli

Type Ii Pneumocytes

Irregular and cuboidal shaped cells which secretes a substance called Surfactant

Surfactant

The internal area of an alveoli is provided with a thin layer of fluid called as

Surfactant secreted by type II cells.

Function Of Surfactant

1. It reduces the internal surface tension of alveoli which prevent it collapsing

during expiration.

2. It increases the compliance.

3. It stabilize the alveoli.

4. It also helps to keep the alveoli dry.

Lungs



Lungs are paired, soft, spongy, elastic and highly vascularized structures, which

occupy most of thoracic cavity. In child, they are pink, but with age they

become dark and mottled due to inhalation of dust.

Right Lung

Partitioned into 3 lobes by two fissures.

Left Lung

Divided into 2 lobes by one fissures.

Pleural Membranes

Each lung is enclosed by two thin membranes called as Visceral and parietal

pleural membranes.

Pleural Cavity

In between the membranes there is a narrow cavity, the pleural cavity filled with

pleural fluid which acts as lubricant.

Function Of Cavity

1. Cardinal function is to exchange gases.

2. Phagocytosis of air borne particles

3. Temperature regulation

4. Removal of water

5. Maintainence of acid-base balance (by elemination of CO2)

6. Acts as Reservoir of blood.

Breathing

Definition:

“Breathing is the process of taking in (inspiration or inhalation) and giving out

of air (expiration or exhalation) from the atmosphere up to the respiratory

surface and vice versa”

Types Of Breathing

There are two types of Breathing

• Negative pressure Breathing

• Positive pressure Breathing

Negative Pressure Breathing

Normal breathing in man is termed as negative pressure breathing in which air

is drawn into the lungs due to negative pressure (decrease in pressure in thoracic

cavity in relation to atmospheric pressure).



Positive Pressure Breathing

“In this kind of breathing, lungs are actively inflated during inspiration under

positive pressure from cycling valve”.

Examples

Frog uses positive pressure breathing.

Phases Of Breathing

1. Inspiration Or Inhalation

2. Expiration Or Exhalation

(1) Inspiration

Definition:

“Inspiration is an energy consuming process in which air is drawn into the lungs

due to negative pressure in thoracic cavity”

Mechanism

During inspiration volume of thoracic cavity increases which creates a pressure

(intra thoracic) that sucks the air into the lungs.

Increase In Volume Of Thoracic Cavity

Volume of thoracic cavity increases due to

1. Inc. in Anterio-posterior diameter

2. Inc. in Vertical diamter.

Increase In Anterio-Posterior Diameter

During contraction of external intercostals muscle, the ribs as well as the

sternum move upward and outward, which causes the increase in anterior-

posterior diameter of thoracic cavity.

Increase In Vertical Diameter

Vertical diameter of thoracic cavity inc. due to Contraction (descent) of

Diaphragm which makes it flat.

• As a consequence thoracic cavity enlarges and the pressure is developed

inside the thoracic cavity and ultimately in the lungs. So the air through

the respiratory tract rushes into the lungs upto the alveoli where gaseous

exchange occurs.

(2)Expiration

Definition:



“It is reserve of inspiration. The passive process in which air is given out of

lung due to increased pressure in thoracic cavity is called “Expiration”

Mechanism

During expiration, elastic recoil of pulmonary alveoli and of the thoracic wall

expels the air from the lungs.

Decrease In Volume Of Thoracic Cavity

Volume of thoracic cavity ↓ due to

1. Decrease In Anterio-Posterior Diameter

2. Decrease In Vertical Diameter

(1) Decrease In Anterio-Posterior Diameter

It is caused by relaxation of external intercostals muscles and contraction of

internal intercostals muscles which moves the ribs and sternum inward and

downward.

(2) Decrease In Vertical Diameter

It is caused by relaxation of diapharagm which makes it dome shaped thus

reducing the volume of thoracic cavity.

• As a consequence, the lungs are compressed so the air along with water

vapours is exhaled outside through respiratory passage.

Control Of Rate Of Breathing

Rate of breathing can be controlled by two modes.

• Voluntary Control

• Involutary Control

Voluntary Control

Breathing is also under voluntary control by Cerebral Cortex.

Examples

We can hold our breath for short time or can breathe faster and deeper at our

will.

Involuntary Control

Mostly, rate of breathing is controlled automatically. This is termed as

Involuntary control which is maintained by coordination of respiratory and

cardio-vascular system.



Two Modes Of Involuntary Control

A. Nervous Control (through respiratory centers in brain)

B Chemical Control (through chemoreceptors)

(A) Nervous Control

• Control of rate of breathing by nervous control is through the Respiratory

centers in Medulla oblongata which are sensory to the changes in Conc.

of CO2 and H+ present in the cerebro-spiral fluid (CSF).

Respiratory Centres In Medulla

Two center are present

(1) Dorsal Group Of Neurons

Medulla contains a dorsal group (Inspiratory group) of neurons responsible for

inspiration

Function

In response to increase conc. of CO2 and H+ (decreased pH), it sends impulses

to the intercostals muscles to increase the breathing rate

(2) Ventral Group Of Neurons

Another area in the medulla is ventral (expiratory) group of neurons.

Function

It inhibits the dorsal group and mainly responsible for expiration

(B) Chemical Control

Chemical control of rate of breathing is through chemoreceptors.

Location Of Chemoreceptors

• Aortic Bodies

• Carotid Bodies

Aortic Bodies

The peripheral chemoreceptors which are located above and below the arch of

aorta are called Aortic bodies. It sends impulses to medulla through Vagus

nerve.

Carotid Bodies

Chemoreceptors which are located at the bifurcation of carotid arteries are

called Carotid bodies. It sends impulses to medulla through Glossopharyngeal

nerve.



Function

Inc. in concentration of CO2 and H+ in blood are basic stimuli to increase the

rate of breathing which are monitered by these chemoreceptors and then send

the impulses to medulla oblongata which produce action potential in inspiratory

muscles.

Disorders Of Respiratory Tract

(1) Lung Cancer (Bronchial Carcinoma)

Causes

• Smoking is a major risk factor either acitively or passively.

• Asbestos, nickel, radioactive gases are associated with increased risk of

bronchial cascinoma

Physiological Effects

+ Loss Of Cilia

The toxic contents of smoke such as nicotine and SO2 cause the gradual loss of

cilia of epithelical cells so that dust and germ are settled inside the lungs.

+ Abnormal Growth Of Mucous Glands Tumor arises by uncontrolled and abnormal growth of bronchial epithelium

mucous glands. The growth enlarges and sometimes obstruct a large bronchus.

• The tumours cells can spread to other structures causing cancer.

Symptoms

• Cough- due to irritation

• Breath lessness – due to obstruction.

(2)Tuberclosis (Koch’s Disease)(Infectious Disease Of Lung)

Cause

Caused by a Bacterium called as “Mycobecterium Tuberclosis”


• Tuber Bacili causes

• Invasion of infected region by macrophages

• Fibrosis of lungs thus reducing the total amount of functional lung tissues



These effects cause

• Increased work during breathing

• Reduced vital and breathing capacity

• Difficulty in diffusion of air from alveolar air into blood.

Symptoms

• Coughing (some time blood in sputum)

• Chest pair

• Shortness of breath

• Fever

• Sweating at night

• Weight loss

• Poor apetite

Prevention

A live vaccine (BCG) provides protection against tuberclosis.

3.Copd-(Chronic Obstructive Pulmonary Disease)

They include

A. Emphysema

B. Asthma

(3-A)Emphysema

Causes

It is a chronic infection caused by inhaling Smoke and other toxic substances

such as Nitrogen dioxide and Sulphur dioxide


• Long infection – Irritants deranges the normal protective mechanisms such

as loss of cilia, excess mucus secretion causing obstruction of air ways

• Elasticity of lung is lost

• Residual volume increases while vital capacity decreases.

• Difficulty in expiration due to obstruction

• Entrapment of air in alveoli

• All these together cause the marked destruction of as much as 50-80% of

alveolar walls.

• Loss of alveolar walls reduces the ability of lung to oxygenate the blood

and remove the CO2

• Oxygen supply to body tissues especially brain decreases.

Symptoms



• Victim’s breathing becomes labored day by day.

• Patient becomes depressed, irritable and sluggish.

• Concentration of CO2 increases which may cause death.

(3-B) Asthama

“Respiratory tract disorder in which there are recurrent attacks of

breathlessness, characteristically accompanied by wheezing when breathing

out.”

Causes

It is usually caused by Allergic hypersensitivity to the plant pollens, dust,

animal fur or smoke or in older person may be due to common cough.

Heridity is major factor in development of Asthma.


• Localized edema in walls of small bronchioles.

• Secretion of thick mucus.

• Spastic Contraction of bronchial smooth muscles (so the resistance in air

flow increases).

• Residual volume of lung increases due to difficulty in expiration.

• Thoracic cavity becomes permanently enlarged.

Symptoms

• The asthmatic patient usually can inspire quite adequately but has great

difficulty in expiring.

Lung Capacities

1. Total Average Lung Capacity

Definition:

“It is the maximum volume in which the lung can be expanded with greatest

possible inspiratory efforts.”

Or

“Total lung capacity is the combination of residual volume and vital capacity.

Value

Total lung capacity = 5000 cm3 or 5 lit of air.

2. Tidal Volume

“The amount of air which a person takes in and gives out during normal

breathing is called Tidal Volume.”



Value

450cm3 to 500 cm3 (1/2 litre)

3. Inspiratory Reserve Volume

Definition:

“Amount of air inspired with a maximum inspiratory effort in excess of tidal

volume.”

Value

200 cm3 or 2 lit. (Average value)

4. Expiratory Reserve Volume

Definition:

“Amount of air expelled by an active expiratory effort after passive

expirations.”

Value: 1000 cm3 or 1 litre.

5. Vital Capacity

Definition:

“After an extra deep breath, the maximum volume of air inspired and expired is

called Vital capacity.”

Or

“It is the combination of inspiratory reserve volume, expiratory reserve volume

and tidal volume.”

Value

Averages about 4 litre.

6. Residual Volume

Definition:

“Amount of air which remains in lung after maximum expiratory effort is called

Residual volume.”

Value

Approximately 1 litre or 1000 cm3.

Importance Of Lung Capacity

• Residual volume prevents the lung from collapsing completely.

• Responsible for gaseous exchange in between breathing.

• It is not stagnant since inspired air mixes with it each time.

• Aging or Emphysema, etc can increase the residual volume at the expense

of vital capacity.



Haemoglobin

Introduction

“Haemoglobin is an iron containing respiratory pigment present in the red blood

cells of vertebrates and responsible for their red colour.”

Structure

Haemoglobin consists of

1. Heme

2. Protein (globin like chains)

1. Heme

One Haemoglobin molecule consists of 4 molecules of Heme. Each Heme

molecule contains an iron (Fe++) binding pocket. Thus, one molecule of

Haemoglobin can combine with 4 iron atoms.

2. Globin

Each Hb molecule contains four globin like chains (Two α chains and Two β

chains).

Role Of Hb During Respiration

Two major functions are performed by Hb.

1. Transport of O2 from lung to tissues.

2. Transport of CO2 from tissues to lungs.

1. “Transport Of O2 From Lungs To Tissues”

“Nearly 97% of O2 is transported from the lungs to the tissues in combination

with Hb.”

Attachment Of O2 With Hb

It is the iron of Hb molecule which reversibly binds with oxygen. One Hb

molecule can bind 4 molecules of O2. Thus, due to Hb, blood could carry 70

times more oxygen than plasma.

Mechanism Of Transport

• Due to high O2 concentration in alveolar air, the O2 moves from air to the

venous blood where O2 concentration is low.

• It combines loosely with Hb to form Oxyhemo Globin.

• In this form, O2 is carried to the tissues where due to low oxygen

concentration in tissues, oxy Hb dissociates releasing oxygen, which enters

in tissues.



Whole process can be represented by following equation.

2. “Transport Of Co2 From Tissues To Lungs”

“Haemoglobin is also involved in 35% of transport of CO2 from tissues to

alveolar blood capillaries in alveoli.”

Attachment Of CO2 With Hb

CO2 binds reversibly with NH2 group of Hb to form loose compound called

“Carboamino Haemoglobin.”

Mechanism Of Transport

• Carbon dioxide due to its higher concentration in tissue diffuses out into

the blood where it combines with Hb to form Carboamino Hb.

• In the alveoli it breaks and CO2 diffuses out into the Alveoli from where it

is expired.

Myoglobin

Introduction

“Myoglobin is a heme protein, smaller than Hb, found in muscles and giving red

colour to them.

Structure

Myoglobin consists of one heme molecule and one globin chain. It can combine

with one iron (Fe++) atom and can carry one molecule of O2.

Function Of Myoglobin

• Myoglobin has high affinity for O2 as compared to Haemoglobin so it binds

more tightly.

• It stores the O2 within the muscles.

• It supplies the O2 to the muscles when there is severe oxygen deficiency

(During exercise)

It can be represented as follows:

Mb + O2 ↔ MbO2

Transport Of Gases

Oxygen and carbondioxide are exchanged in, Alveoli by Diffusion.

O2 Transport



Blood returning into the lungs from all parts of body is depleted from oxygen.

This deoxygenated blood is dark maroon in colour to appear bluish through

skin. It becomes oxygenated in the lungs.

Two Forms Of O2 In Blood

O2 is transported in the blood in two forms:

• Dissolved form (3%)

• Combination with Hb (97%) ® Oxyhaemoglobin

Mechanism Of O2 Transport

+ Diffusion Of O2 From Alveolus Into Pulmonary Blood

The air inhaled into the lungs has high concentration of oxygen while venous

blood in pulmonary capillaries has low in concentration. Due to this difference

in concentration across the respiratory surface, oxygen diffuses into the blood

flowing into capillaries around the Alveoli. Now blood becomes oxygenated

which is bright red in colour.

+ Diffusion Of O2 From Capillaries Into Cells

Concentration of O2 in the arterial end of capillaries is much greater than

concentration of O2 in the cells. So, O2 diffuses from the blood to the body cells.

Since the blood takes in oxygen much more rapidly than water. Thus, it can

transport enough oxygen to the tissues to meet their demand.

CO2 Transport

Blood returning from tissues contain excess of CO2 as a respiratory by-product,

which is eliminated from the body during expiration in the lungs.”

Three Forms Of CO2 in Blood

* Dissolved form (in plasma) – 5%

* In form of HCO3- (in RBC’s) – 60%

* In combination with Hb (Carboamino Hb) – 35%

+ Dissolved Form

Only 5% of CO2 is transported in dissolved form in plasma. Here it combines

with H2O of plasma to form H2CO3. But this reaction is very slow as plasma

does not contain Carbonic Anhydrase to accelerate this reaction.

Reactions can be represented by following equations.

CO2 + H2O ↔ H2CO3

H2CO 3 ↔HCO3- + H+

HCO3- + k+ ↔ KHCO3



+ In Form Of HCO3-

60% of CO2 is transported in the blood in form of HCO3- in RBC’s. Here it

combines with water to form H2CO3. But this reaction occurs rapidly in RBC’s

due to presence of Carbonic Anhydrase.

Reactions can be represented by following equations

CO2 + H2O ↔ H2CO3

H2CO3 ↔ HCO3- + H+

HCO3- + Na+ ↔ NaHCO3

+ In Combination With Hb

As discussed previously in role of Hb.

Mechanism Of CO2 Transport

+ Diffusion Of CO2 From Cells Into Capillaries

CO2 is continuously synthesizing in the tissues as a result of metabolism. Thus,

due to its higher concentration. CO2 diffuses from the tissues into blood, which

becomes deoxygenated.

+ Diffusion Of CO2 From Pulmonary Blood Into Alveolus

Blood returning from tissues contain high concentration of CO2. This blood is

brought to lungs, where CO2 diffuses from the blood into alveolus where its

concentration is lower.

Factors Effecting The Transport Of Gases

Following are some factors, which influence the transport of respiratory gases

across the alveolar wall.

1. Concentration Gradient

2. Presence of competitor such as CO

3. Moisture

4. Surfactant

5. pH



CHAPTER 14

TRANSPORT

Diffusion

The movement of ions or molecules from the region of higher concentration to

the region of lower concentration is known as diffusion.

Examples

1. If a bottle of perfume is opened in a corner of a room, it can be smelt in the

entire room.

2. Leakage of gas pipes can be smelt from a farther point.

3. If we drop a KMNO4 crystal in clean water, then after sometime the crystals

will dissolve and colour of water changes from colorless to purple.

Factors On Which Rate Of Diffusion Depends

1-Size

Small molecules move faster than larger ones.

2-Temperature

Rate of diffusion will be high at high temperatures.

3-Concentration Gradient

Greater the difference in concentration and shorter the distance between two

regions, greater will be the rate of diffusion.

Facilitated Diffusion

Diffusion of the substances across the cell membrane through the specific

carrier proteins are known as facilitated diffusion. These membrane transport

proteins are channel proteins, receptors, cell pumps or carriers, made up of

usually proteins and don’t require energy for transport.

Passive Transport



Movement of substances in and out of the cell, caused by simple kinetic motion

of molecules, doesn’t require energy of ATP is known as passive transport, e.g.

Simple diffusion and facilitated diffusion.

Osmosis

The movement of water molecules from the region of higher concentration to

the region of lower concentration through a semi-permeable membrane, is

known as osmosis.

Types Of Osmosis

A- Endosmosis

The movement of water molecules into the cell, when it is placed in hypotonic

solution is called as Endosmosis.

B- Exomosis

The movement of water molecules out of the cell when the cell is placed in a

hypertonic solution.

Active Transport

The movement of ions or molecules across the cell membrane against the

concentration gradient i.e. from lower concentration to higher concentration

with the help of specific transport proteins in the cell membrane, at the expense

of cell’s metabolic energy – ATP is called active transport.

Examples

1. Sodium-Potassium pump in nerve cells which pump Na+ out of the nerve

cell, and K+ into the cell against the concentration gradient.

2. Cells lining the intestine can transport glucose actively from a lower

concentration in the intestinal contents to higher concentration in blood.

3. In plants phloem loading is an ex. Of active transport.

Imbibitions

Adsorption of water and swelling up of hydrophilic (water loving) substances is

known as imbibitions.

Hydrophilic Substances

Those which have great affinity for water are hydrophilic e.g. starch, gum,

protoplasm, cellulose, proteins, e.g. seeds swell up when placed in water.

• Wrapping up of wooden framework during rainy seasons.

• Dead plant cells are hydrophilic colloids.



• The chemical potential of water is a quantitative expression of the free

energy associated with the water.

• UNIT: Joules/mole

• This term has been replaced by water potential

Water Potential (PSI)

It is the difference between the fee energy of water molecules in pure water and

energy of water in any other system, or solution. Water potential is a relative

quantity, depends upon gravity and pressure.

Q = Q* + f (concentration) + f (pressure) + f (gravity)

Β* is standard water potential or pure water potential of valve O Mpa.

Unit : Megapascal’s – MPa

(1 Mpa = 9.87 atmospheres)

Uses

The direction of water flow across cell membrane can be determined. It is a

measure of water status of the plant.

Osmotic Pressure

The pressure exerted upon a solution to keep it in equilibrium with pure water

when the two are separated by a semi permeable membrane is known as

Osmotic pressure.

It prevents the process of osmosis.

Osmotic Potential

The tendency of a soln to diffuse into another, when two solutions of different

concentrations are separated by a differentially permeable membrane.

• It is represented by βs for pure water βs = 0

• The βs decrenses as the osmotic concentration increases.

• Osmotic concentration is the number of osmotic-ally active particle per

unit volume.

• Osmotic potential has been replaced by solute potential.

• The concentration of solute particles in a solution is known as solute

potential βs. It value is always negative.

Pressure Potential Βp



When a cell is placed in pure water or in aqueous solution with higher water

potential than the cell sap water follows into the vacuole by endosmosis thru

cell membrane and tonoplast. Due to this inflow of water, the tension developed

by the cell wall causes an internal hydrostatic pressure to develop, which is

called as pressure potential.

Β = βs + βp or Qp = Q – Qs

In turgid cells βp is equal and opposite to βs

Turgid Cell

When the cell is fully stretched with maximum pressure potential, the water

cannot flow into it. This condition is called turgidity and the cell is turgid.

Plasmolysis

If a cell is placed in a hypertonic solution, which has more negative solute and

water potentials then water will come out of the cell, by exosmosis and

protoplasm starts separating from cell wall leaving a gap between cell wall and

cell membrane. This withdrawal of protoplasm from cell wall is known as

plasmolysis.

The point where protoplasm just starts separating from cell wall is known as

“Incipient plasmolysis” when it is completely separated, full plasmolysis occurs.

In plasmolysis cell βp = 0 therefore βw = βs

Deplasmolysis

When a cell is placed is a hypotonic solution or pure water, there will be an

inflow of water by endosmosis. Protoplasm starts expanding and presses cell

wall due to which pressure potential develops and water potential becomes less

negative. This swelling of cell is known as deplasmolysis.

Water And Minerals Uptake By Roots

1. Absorption of water and mineral salts takes place through root system.

2. Roots are provided with enormous number of tiny root hairs.

3. These root hairs are more in number in tap root system.

4. Roots hairs are out growths of epidermal cells.

5. Roots hairs increase the surface area for absorption.

6. Most of the absorption takes place at root tips.

7. From hairs and epidermal cells water flows thru cortex, endodermis,

pericycle and them enters xylem.

There are 3 pathways for water to enter xylem.



A- Cellular Pathway

In this route water flows through cell to cell. Water enters the root hairs or

epidermal cells down a concentration gradient: it flows through cell wall and

cell membrane and enters the adjacent cell from where water may again flow

towards the deeper cells by osmosis.

B- Symplast Pathway

Cytoplasm of the cortical cells are interconnected by small pores in the cell wall

known as plasmodesmata.

These pores provide another way of transporting water and solutes across the

plasma membrane at root hairs.

C- Apoplast Pathway

The cell walls of cortical and epidermal cells are hydrophilic and form a

continuous matrix. Soil solution flows freely through these hydrophilic walls.

The movement of soil soln.through extra cellular pathway provided by

continuous matrix of cell walls is known as “Apoplast pathway”.

Simplast and apoplast usually both occur concurrently.

Endodermis forms a waxy barrier against the flow of water and salts known as

“casparion strip”. So, water cannot enter endodermis via apoplast pathway.

Symplast is the only way to cross the barrier. Endodermal cells actively

transport salts to pericycle resulting in high osmotic potential which causes

inflow of water by osmosis salts. Form pericycle water flows in to xylem via

both symplast and apoplast pathways.

Transpiration

The loss of water in the form of vapours from aerial parts of the plant is called

transpiration.

Types Of Transpiration

Following are the three types of transpiration.

A- Stomatal Transpiration

It is a type of transpiration in which the water vapours escape through the

stomata. 90% of the total transpiration occur thru this method. In isobilateral

leaves the stomata are present in both upper and lower epidermis e.g. lily and

maize leaves. In dorsiventral leaves, the stomata are only confined to lower

epidermis e.g. Brassica and sunflower.



B- Cuticular Transpiration

The loss of water in the form of vapours through the cuticle of leaves is called

Cuticular Transpiration. About 5-7% of total transpiration takes place thru this

route cuticle is a waxy layer which covers the leaves and this is not completely

impermeable to water.

C- Lenticular Transpiration

It is the loss of water vapours through lenticles present in the stems of dicot

plants. Lecticles are aerating pores present in the bark formed as a result of

secondary growth. It accounts for only 1-2% of total transpiration.

Mechanism Of Stomatal Respiration

Structure Of Stomata

Stomata are microscopic pores present in the epidermis of leaves and

herbaceous stems. Number of stomata are variable in different leaves and

depend upon the availability of water and climate of the region. Each stomata is

surrounded by 2 specialized epidermal cells, as guard cells, they are bean

shaped or kidney shaped and unlike other epidermal cells, they contain

chlorophyll, hence perform photo-synthesis. The inner wall of guard cell is thick

while the outer wall is thin and elastic. This structural difference is important

for opening and closing of stomata.

Stages Of Transpiration

There are two processes involved in stomata transpiration.

+ Evaporation

In the first step, water evaporates from the wet surfaces of turgid mesophyll

cells and collected in the intercellular air spaces.

+ Diffusion

In this stage water vapours diffuse out from intercellular spaces where they are

in higher concentration to the outer atmosphere where they are in lower

concentration through the stomata.

Mechanism Of Opening And Closing Of Stomata

The opening and closing of stomata depends upon the turgidity of guard cells,

which is due to increase or decrease in the osmotic potential of the guard cells.

When water enters the guard cells by osmosis, they swell up. Since their outer

walls are thin and elastic, they stretch and bulge out. The inner thick walls

cannot stretch and so arch in and become crescent shaped thus the gap between

the two guard cells widens, opening the stomata when the guard cell lose water,



they become flaccid and the inner wall of two guard cells meet each other,

closing the stomata.

Generally, the stomata remain open during day time and close at night. Thus,

light appears as the primary factor which control the opening and closing of

stomata.

Factors Regulating Opening And Closing Of Stomata

There are two main factors which greatly influence the opening and closing of

stomata these are;

1- Light

In the presence of light, chlorophyll containing guard cells synthesize sugars

which is turn increase the osmotic potential of guard cells. This increase Qs

results in endosmosis and ultimately to turgidity. While in darkness these guard

cells consume carbohydrates (sugars) by respiration for energy production or

transported to other neighbouring cells for respiration and different purposes.

This decreases the osmotic potential of guard cells leading to flaccidity because

of exomosis of water.

2- Concentration Of K+ Ions

Turgidity of guard cells of many plants is regulated by K+ ion concentration.

During daytime, guard cells actively transport K+ions into them from

neighbouring cells. Accumulation of K+ ions lower the water potential of guard

cells. This causes on inflow of water by endosmosis from epidermal cells.

During night when they lose K+ ion, water potential increases. Water flows out

of the guard cells by exosmosis causing them to become flaccid which result in

closure of pore.

Factors Affecting Transpiration

Rate of transpiration is very important for a plant because transpiration stream is

necessary to distribute dissolved mineral salts throughout the plants. Water is

transported to photosynthesizing cells of leaves. Transpiration is also very

important as it cools the plant. This is especially important in higher

temperatures. If the rate of transpiration is very high, there would be much loss

of water from the plant. So, at high temperatures the stomata almost close and

reduction in the rate of transpiration is affected. This stops witting of the leaves

and of herbaceous stems of plants.

Following are some important factors which affect the rate of transpiration.

1. Light



Light affects the transpiration in two ways:

a. Light regulates the opening and closing of stomata. During sunshine, the

stomata are open, losing water vapours thus rate of transpiration is high and

during night, the stomata are closed, so the rate of transpiration is low.

b. Greater intensity of light, increases the temperature and warms the leaf, so

leaves lose heat by evaporating water molecules to cool themselves.

2. Temperature

Plants transpire more rapidly at higher temperature than at low. Rise in

temperature has two effects:

i. It increases kinetic energy of water molecules, which results in rapid

evaporation of water and decreases the rate of transpiration.

ii. High temperature reduces the humidity of surrounding air. Due to this,

evaporation from surfaces of mesophyll cells increase and hence rate of

transpiration.

3. Wind

The air in motion is called wind. The area around the stomata is saturated with

water vapours due to transpiration. During high velocity wind the area around

leaves is quickly replaced by fresh drier air which increases diffusion of water

molecules from air spaces to outside atmosphere and increases the rate of

transpiration.

When air is still, the rate of diffusion of water molecules is reduced and the rate

of transpiration is also reduced.

4. Humidity

When air is dry, the rate of diffusion of water molecules, from the surfaces of

mesophyll cells, air spaces and through stomata, to outside the leaf increases.

So, more water is lost, increasing the rate of transpiration.

In humid air, the diffusion of water molecules is reduced. This decreases the

rate of transpiration.

5. Soil Water

A plant can’t continue to transpire rapidly if its moisture loss is not made up by

absorption of fresh supplies of water from the soil. When absorption of water by

roots fails to keep up with rate of transpiration, loss of turgor occurs and wilting

of leaf takes place.



Disadvantages Of Transpiration

1. Transpiration is said to be necessary evil because it is an inevitable, but

potentially harmful, consequence of the existence of wet cell surfaces from

which evaporation occurs.

2. High rate of transpiration causes water deficiency and thus the excessive

transpiration leads to wilting and death of plants.

3. There is good evidence that even mild water deficiency results in reduced

growth rate of plants.

4. Excessive transpiration effects the protein synthesis, sugar synthesis and

other metabolic activities of plants.

Advantages Of Transpiration

1. Water is conducted in most parts of plants due to transpiration pull or ascent

of sap.

2. It causes absorption of water and minerals from the soil.

3. Minerals dissolved in water are conducted throughout the plant body by

transpiration stream.

4. Evaporation of water from the exposed surface of cells of leaves has cooling

effect on plant.

5. Excess water is removed.

6. Wet surface of leaves allow gaseous exchange.

Guttation

It is the loss of water in the form of droplets from the ends of large leaf-veins. It

takes place through special openings called hydathodes.

Differences Between Transpiration And Guttation

Transpiration

• Water escapes in the form of wapours.

• Escape water is pure and does not contain solutes.

• It takes place through stomata, and cuticle.

• It is regulated by stomata.

• Normally takes place in light

Guttation



• Water escapes as liquid.

• Escaped water contains solutes.

• It takes place through hydathodes and end of veins.

• It is not a regulated process.

• Takes place at night.

Translocation Of Organic Solutes

Transport of organic products of photosynthesis, like sugars from mature leaves

to the growing and storage organs in plants is called translocation. This

movement of photo assimilates and other organic materials takes place via the

phloem and is therefore called “Phloem Translocation.”

The phloem is generally found on the outer side of xylem and constitutes the

bark. The cells of phloem that take part in phloem translocation are called sieve

elements. Phloem tissue also contains companion cells, parenchyma cells, fibres

like sclereids latex containing cells. But only sieve tube cells are directly

involved in tansport of organic solutes.

Source to Sink Movement

The translocation of photosynthesis always takes place from source to sink

tissues, therefore, the phloem transport is also referred as “source to sink

movement.”

Source

The part of plant which forms the sugars or photoynthates is known as source.

For example, Mature Leaves.

Sink

Sinks are the areas of active metabolism or storage of food e.g: Roots, Tubers

developing fruits, immature leaves, growing tips of roots and shoots. Some

source and sinks are interconvertible during the process of development of

plants. For example: developing and mature leaves, developing and germinating

seeds, root of sugar beets etc.

Munch Hypothesis (Mechanism Of Phloem Translocation)

Phloem translocation is mainly explained by a theory called the “Pressure flow

hypothesis” proposed by Ernest munch in 1930 which explains the steps

involved in the movement of photosynthates from mesophyll chloroplasts to the

sieve elements of phloem of mature leaves.

Steps

The following steps explain flow theory:



1. The glucose formed during photosynthesis in mesophyll cells, is used in

respiration or converted into non-reducing sugar i.e. sucrose.

2. the sucrose is actively transported to bundle sheath cells and then to

companion cell of the nearest smallest vein in the leaf. This is called “short

distance transport” because solutes cover only a distance of two or three cells.

3. Sucrose diffuse into sieve tube cell or sieve elements by symplast pathway or

apoplast pathway. This is called phloem loading, this raises the conc. of sugars

in sieve elements, which causes osmosis of water from nearby xylem in the leaf.

It causes an increase in the hydrostatic pressure or tugor pressure.

4. The increase hydrostatic pressure moves the sucrose and other substances in

the sieve tube cells, and moves to sinks. The photo-assimilates (sugars etc) can

be moved a long distance i.e. of several meters, therefore this is known as

“Long distance transport.”

5. In the sink tissues, present at the other end of pathway, sugars are delivered

by phloem by an active process called “Phloem Unloading.” It produces a low

osmotic pressure in sieve elements of sink, as a result of this water potential

begins to rise in the phloem and causes an exosmosis of water molecules from

the sieve tubes. This causes a decrease in turgor pressure of the sieve tubes

(phloem).

6. The presence of sieve plates in the sieve elements greatly increases the

resistance along the pathway and results in the generation and maintenance of a

substantial pressure gradient in the sieve elements between source and sink. The

sieve elements contents are physically pushed along the traslocation pathway by

bulk flow, much like water flowing through a garden house.

Significance Of Translocation

1. Food can be formed or stored as in sugar beet’s root or stem of sugar cane.

2. Sucrose is transported to sink where it is converted to glucose and used as

energy.

3. Productivity of crop can be increased by accumulation of photo-synthates in

edible sink tissues like cereal grains, pulses, ground nuts etc.

4. Fruit is forme by this process e.g. Apples, Mango etc.

Ascent Of Sap



The upward movement of water and dissolved mineral salts from the roots to

the leaves against the downward pull of gravity is known as “Ascent of Sap.”

Path Of Movement

The distance traveled by water is small and easy in plans like herbs and shrubs

and longest in tall trees like pinus, red wood, eucalyptus etc. For transport,

different tissues of xylem are used for conduction of water in different plants.

These are open ended cells called “Vessels” and porous cells called “tracheids”

(Fig. From book).

A. Vessels

1. These are thick walled tube like structures which extend through several feet

of xylem tissue.

2. They range in diameter from 20μm to 70μm.

3. Their walls are lignified and perforated by pits. At the pit, cell wall is only

made up of cellulose. Pits of adjacent cells match up with each other, so that

their cavities are interconnected.

4. Xylem vessels arise from cylindrical cells, which placed end to end. They die

at maturity forming a continuous duct, providing a channel for long-distance

transport of water.

5. Rate of flow of water is 10 times faster than tracheids.

Occurance

Vessels are mostly found in Angiospermic plants.

B. Tracheids

1. These are individual cells about 30μm in diameter. They are several mm long

and tapered.

2. Like vessels, they are also dead, made up of thick lignified walls.

3. Their walls are perforated by small pits, which are of two types, simple and

bordered.

4. The Tracheids are connected by pits and forming a long channel for

conduction of water.

Occurance

In Ferns and Conifers.



Mechanism Of Ascent Of Sap

Water and dissolved mineral salts present in xylem, flow in upward direction at

the rate of 15m/hour. Xylem sap ascends because of two reasons:

1. Push from below – Root Pressure Theory

2. Pull from above – Dixon’s Theory

1. Root Pressure Theory

According to Stephen Hales:

“The force which is responsible for the upward movement of water molecules in

xylem is by the pushing effect from below (i.e. roots) and is known as “Root

Pressure.” Root Pressure is created by active secretion of sals and other solutes

from the other cells into xylem sap.

This lowers the water potential of xylem sap. Water enters by osmosis, thus

increasing the level of sap. Water also take apoplast or symplast pathway to

enter the xylem cells, this increased level causes a pressure effect in xylem and

pushes the water upwards.

Objections/Failure Of Theory

1. This force is unable to push water in tall plants.

2. It is seasonal.

3. Completely absent from Cycads and Conifers, so how they transfer water.

4. When a cut shoot is placed in water, the water rises in shoots although roots

are absent.

5. It is also present in plant which donot have well developed root system.

2. Transpiration Pull (Dixon’s Theory) Or Adhesion-Cohesion-Tension

Theory

Dixon and Jolly proposed this theory for ascent of sap. It provides a reasonable

explanation of flow of water and minerals from the roots to leaves of plants. It

depends on:

Adhesion

Adhesion is the sticking together of molecules of different kinds. Water

molecules adhere to the cell walls of xylem cells, so that the column of water in

xylem tissue doesn’t break. The cellulose of cell wall has great affinity for

water, which helps in the process.



Cohesion

Cohesion is the attraction among molecules of same kind, which holds water

molecules together, forming a solid chain-like column within the xylem tubes.

Extensive hydrogen bonding in water gives rise to property of cohesion. The

molecules of water in xylem tube form a continuous column.

Transpiration Pull

The loss of water from the aerial parts of the plant especially through stomata of

leaves is called transpiration.

During daytime, the leaf after absorbing sunlight, raising its temperature starts

transpiration. When a leaf transpires, the water potential of its mesophyll cells

drop. This drop causes water to move by osmosis from the xylem cells of leaf

into dehydrating mesophyll cells.

The water molecules leaving the xylem are attached to other water molecules of

tube by H-bonding.

Therefore, when one water molecules move up the xylem, the process continues

all the way to the root, where water is pulled from the xylem cells, i.e. tracheids

or vessels.

Due to this pulling force or transpiration pull, water in xylem is placed under

tension which is transmitted to root through vessels. Tension is due to H-

bonding and strong cohesive forces between water molecules, and is strong

enough to pull water upto 200 metres or even more.

Ascent of Sap is Solar Powered

To transport water over a long distance, plants do not use their metabolic energy

or ATPs. It is done only by forces like adhesion, cohesion, evaporation and

presence of sunlight. Thus, ascent of sap is “Solar Powered.”

Significance of Ascent of Sap

• Water can be transported to the different parts of the plant.

• Transpiration is regulated.

• Food is formed in presence of water.

• Photosynthesis requires water.

• Salts and minerals are also absorbed along water by roots.

biology first year complete 14 chapters

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