Preliminary Biology: Topic Summary

Patterns in Nature Matt Elrick

1. Organisms are made of cells that have similar structural characteristics

1.1 Outline the historical development of the cell theory, in particular, the contributions of

Robert Hooke and Robert Brown.

Before the invention of lenses and microscopes it was believed that living matter could come from

non-living matter, such as maggots coming from dead things.

Malpighi (1628-1694) first to use lenses to magnify things

Leeuwenhoek (1632-1723) constructed microscope better than others at the time; discovered

microbes in rainwater; discovered yeast cells, bacteria and protozoa.

Hooke (1635-1703) designed a compound microscope (more than one lens) to observe cells in

cork. Was first person to use word cell.

Brown (1773 1858) recognised nucleus as regular feature in all plant cells and named it.

Flemming, in 1880, described cell division (mitosis) from his observations on living and stained cells.

Statements of cell theory then followed:

- A cell is a separate mass of living material bounded by a membrane

- Cells are the basic units of life and organisms are made up of cells

- Cells have similar structural characteristics but also show diversity of form and function

The Cell theory states:

- All organisms consist of cells

- All cells arise from pre-existing cells

- The cell is the unit of structure, function, differentiation and reproduction

1.2 Describe evidence to support the cell theory

Evidence to support cell theory comes from direct observations using the microscope.

- Robert Hookes observations of cork cells proved that all living matter is comprised of small

units called cells.

- Walther Flemmings experiment on cell division (mitosis) confirmed that all cells come from pre-existing cells.

- Anton van Leeuwenhoeks observation of unicellular organisms from a drop of stagnant rainwater showed that cells are the smallest units of life that make up even the tiniest organisms.

1.3 Discuss the significance of technological advances to developments in the cell theory

The development of the cell theory went hand in hand with the technological advances in the manufacture of lenses and magnifying devices. Light Microscope: the development of light microscopy has allowed living cells and organelles to be

observed. Can be viewed up to x400 or to x1000 with oil immersion lens. Therefore, only the larger

cell structures were able to be viewed.

In order to view certain structures more easily, a dye is used to stain the cells.

Electron Microscope: uses a beam of electrons rather than light to magnify x25 000 (scanning

electron microscope) or even x1 000 000 (transmitted electron microscope). The beam of electrons

has enabled scientists to view much smaller parts of a cell.

The limitation with an electron microscope is that the specimens are preserved (dead), therefore cell

function cannot be observed. The specimens are dead because the electrons must be kept in a

vacuum to prevent scattering.

Light microscope Electron microscope

Viewing energy source Light An electron beam

Focusing By glass lenses By magnetic lenses

Colour transmission Yes No

Live specimen viewing Yes No

Specimen mounting Glass slide in air Metal background in a vacuum chamber

Magnification Up to 2000 times Up to 1 000 000 times

Resolving power 0.2 micrometres 0.0002 micrometres

Advantages Samples prepare quickly, living samples can be viewed

High magnification and resolution allow particles as small as molecules to be viewed. Expensive and specimens take a while to be prepared.

Disadvantages Limited visible detail Only non-living specimens can be viewed

1.4 Identify cell organelles seen with the current light and electron microscopes

Light Microscope:

- Vacuole

- Nucleus

- Cytoplasm

- Chloroplast

- Cell Wall

- Cell Membrane

Electron Microscope:

- Mitochondria

- Golgi Body

- Endoplasmic Reticulum

- Ribosomes

- Lysosome

1.5 Describe the relationship between the structure of cell organelles and their function

Organelle Structure Function Plant / Animal

Mitochondria Oval shape; Double membrane with inner layer folded to provide larger SA - more reactions can occur.

Site of aerobic respiration - produces ATP

Both

Nucleus Surrounded by double nuclear membrane

Controls cell activities; contains DNA

Both

Nucleolus Small round body composed of RNA and protein

Manufacture of proteins; active part of DNA

Both

Endoplasmic reticulum

Folded membranes in cytoplasm - allow chemical reactions to take place

Connects cell membrane with nuclear membrane, involved in the transport of material

Both

Ribosomes Small black dots within cell. Often attached to ER. Found in cytoplasm, mitochondria and chloroplasts.

Produces protein Both

Golgi body Specialized areas of endoplasmic reticulum

Packages proteins in its vesicles (sacs) before secretion

Both

Cell membranes

Provides border for cell Protects and supports organelles; allows for selective transport

Both

Chloroplast Contains dense sets of membranes look like stacked plates.

Site of photosynthesis; contains chlorophyll and enzymes. The stacked membranes trap light energy.

Plant

Lysosomes Small membrane bound sacs Contains special enzymes that attack and destroy (dissolve) foreign protein entering cell.

Animal

Cell wall Made of cellulose Protects and supports the cell Plant

Vacuole Membrane bound cavity Stores food, water and waste Both

2. Membranes around cells provide separation from and links with the external environment

2.1 Identify the major groups of substances found in living cells and their uses in cell activities

Organic (molecules always contain Carbon atoms)

Carbohydrates:

- Contain Carbon, Hydrogen and Oxygen

- General formula is (CH2O)n where n can be any number

- Basic unit is Glucose, which is used as energy in respiration

- Any excess carbs are stored under skin and around organs as fat

- Plant cells walls are made of cellulose, a complex carbohydrate

There are 3 groups of Carbohydrates:

- Monosaccharides: consists of single sugar unit; glucose, fructose, ribose

- Disaccharides: consists of double sugar unit; includes sucrose (glucose + fructose);

lactose (glucose + galactose). When two organic molecules combine, a water molecule is

produced, this is condensation.

- Polysaccharides: consists of multiple sugar units formed to make huge molecules;

includes starch (2000 3000 condensed glucose molecules); cellulose (more than 2000

condensed glucose molecules)

Lipids

- Contain Carbon, Hydrogen and Oxygen (note - ratio of H:0 is never 2:1)

- Includes fats, oils, waxes and steroids

- Fats contain twice energy of carbs

Proteins

- Contain Carbon, Hydrogen, Oxygen and Nitrogen

- Are large molecules made of smaller molecules (amino acids) joined together

- Most abundant organic molecules in cells needed for growth and repair

- Very important to cell structure and function

Nucleic Acids

- Contain linked sugar molecules, nitrogen bases and phosphate groups

- The base-sugar-phosphate unit is called a Nucleotide

- Two types: DNA and RNA

- RNA (ribonucleic acid), found throughout cell, needed for protein manufacture, contains

sugar ribose

- DNA (deoxyribonucleic acid), found in chromosomes, contains sugar deoxyribose (ribose

with some oxygen missing)

INORGANIC (molecules dont usually contain Carbon atoms)

Water:

- Transport chemicals

- Solvent for chemicals

- Involved in reactions (photosynthesis)

- Medium for reactions to take place

- Regulates temp by changing from liquid to gas using heat

Mineral Salts

- Chlorides, Nitrates, Phosphates, Carbonates etc.

- Help enzymes function in chemical reactions

- Used in structure of macromolecules (calcium in bone, iron in blood)

Gases

- Carbon dioxide and Oxygen

- Used in photosynthesis and respiration

- CO2 can dissolve in water to form a buffer to limit changes in pH

2.2 Identify that there is movement of molecules into and out of cells

All cells have a cell membrane surrounding it; this membrane is selectively permeable. Nutrients can

be taken in by cells and waste products removed. The cell membrane can block out any unwanted

foreign substance and only take in what is needed.

2.3 Describe the current model of membrane structure and explain how it accounts for the

movement of some substances into and out of cells.

The current model of membrane structure shows us that cell membranes are semi-permeable. The

current model states that cell membranes are made up of double layers of phospholipids, proteins

are positioned in a complex pattern within these layers. The proteins control the transport of

substances into and out of the cell.

The Fluid Mosaic Membrane model:

Protein

Phospholipid bilayer

Hydrophilic heads facing out

(water loving)

Hydrophobic tails on inside

(water hating)

2.4 Compare the processes of diffusion and osmosis

Diffusion: A diffusion gradient exists when two areas have a different concentration of a substance,

the substance will move until both concentrations are equal, no energy is needed and is therefore

known as passive transport

Osmosis: The diffusion of water across a semi-permeable membrane.

Similarities Differences

Both involve movement of substances from regions of high to low concentrations.

Diffusion is movement of any substance, Osmosis is water only.

Both travel down a gradient (more per unit volume to less per unit volume of a substance)

Osmosis refers to movement across a membrane, whereas diffusion doesnt necessarily need a membrane

Both dont require energy

2.5 Explain how the surface area to volume ratio affects the rate of movement of substances into

and out of cells

The volume of a cell determines its metabolic needs and waste products. The function of a cell

surface is to control the rate of removal of wastes and absorption of nutrients.

As cell size increases, the surface area to volume ratio decreases.

The decrease in SA:V will limit the efficiency that substances can move in and out. Substances need

to move in and out at rate which will maintain efficient cellular metabolism to allow life processes to

continue. Cells cannot grow too big because substances need to move in and out efficiently.

3. Plants and animals have specialised structures to obtain nutrients from their environment.

3.1 Identify some examples that demonstrate the structural and functional relationships

between cells, tissues, organs and organ systems in multicellular organisms.

Cells in multicellular organisms are specialised to do different jobs, therefore, they show variety of

patterns of shape, size and organisation. What a cell looks like is related to what it does.

Cell: Basic unit of life; Specialised to carry out particular tasks

Tissue: Group of cells with similar structure and function (eg. Skin, muscle, nerve)

Organ: Group of tissue joined together to make a structure with a special function (eg. Stomach, lungs, leaf, roots) Organ System: groups of organs whose functions are closely related (eg. Digestive, reproduction, nervous)

3.2 Distinguish between autotrophs and heterotrophs in terms of nutrient requirements

Autotrophs can make organic materials from water, carbon dioxide and inorganic materials using

the energy from sunlight (through photosynthesis). Plants are autotrophs.

Heterotrophs depend on autotrophs to obtain their nutrients. All animals, fungi and most bacteria

are heterotrophic because they cannot photosynthesise.

3.3 Identify the materials required photosynthesis and its role in ecosystems

For photosynthesis to occur, plants obtain light energy from the sun using chlorophyll and use it to

convert carbon dioxide and water into glucose (sugar) and oxygen.

Photosynthesis is the process by which plant cells capture energy from sunlight and convert it into

chemical energy. All living things ultimately depend on this process. The compounds plants produce

provide nutrients and energy to animals which consume them.

3.4 Identify the general word equation for photosynthesis and outline this as a summary of a

chain of biochemical reactions

Carbon dioxide + water Sugars (glucose) + Oxygen

6CO2 + 12H2O -> C6H12O6 + 6O2 + 6H2O

Photosynthesis is a series of many chemical reactions which happen in different parts of the

chloroplasts.

The process of photosynthesis can be thought of as occurring in two sets of reactions or two stages, although it is actually continuous; the products of the first stage become the raw materials of the second stage.

3.5 Explain the relationship between the organisation of the structures used to obtain water

and minerals in a range of plants and the need to increase the surface area available for

absorption

All cells contain water. The ions dissolved in water are needed by organisms for growth and to

manufacture various body substances. Water uptake must balance water loss in order to survive.

Water: roots and root hairs absorb water from soil by osmosis, roots have large surface area. Roots

have thousands of root hairs, this increases the surface area. The large surface area increases the

rate of water uptake and helps penetrate more soil.

Minerals: occur as ions dissolved in water in soil. If ions are small enough they are taken up by roots

and root hairs. If there is a higher concentration of ions in soil, they will move into roots by diffusion.

If concentration is low, a plant may need to expend energy to actively absorb ions against the

concentration gradient.

Sunlight

Chlorophyll

3.6 Explain the relationship between the shape of leaves, the distribution of tissues in them and

their role

The shape of the lead and distribution of tissues in directly related to the environment in which it

lives. The shape of leaves is usually broad and thin, this allows maximum surface area for absorbing

light and carbon dioxide. It is thin enough that light penetrates to reach every layer of cells for

maximum photosynthesis. Leaves which are spikes reduce water loss. Fleshy leaves store more

water.

Tissue: Structure: Function:

Cuticle Waxy layer, transparent Reduces water loss; allows light through; keeps shape

Epidermis Flattened, transport Layer protects cells; transparent to let light through to cells underneath

Stomates Pores Pores on leaves that permit exchange of gases; H2O evaporates from leaf transpiration; CO2 diffuses into leaf for photosynthesis; O2 diffuses out of leaf

Palisade Mesophyll

Close-packed elongated, many chloroplasts

Cells that photosynthesise; tightly packed under epidermis; maximum light; contains many chloroplasts

Spongy Mesophyll

Loose-packing, few chloroplasts

Large spaces between them for gas exchange

Xylem (vein)

Narrow tube-like cells (dead) Transports water and inorganic material from roots to leaves

Phloem (vein)

Narrow tube-like cells (living) Transports food from leaves to rest of plant

3.7 Describe the role of teeth in increasing the surface area of complex foods for exposure to

digestive chemicals

Digestion begins in the mouth where the teeth break the complex foods into smaller pieces. This

increases the surface area of the food for exposure to digestive enzymes which can attack it and

digest it much faster.

3.8 Explain the relationship between the length and overall complexity of digestive systems of a

vertebrate herbivore and a vertebrate carnivore with respect to:

- the chemical composition of their diet

- the functions of the structures involved

The length of a digestion is related to the type of food eaten by the animal.

Herbivores diets consist of a large amount of cellulose, no digestive enzymes can digest cellulose,

instead microorganisms in the colon (large intestine) convert cellulose into sugars, which is a very

slow and inefficient process. The long length of the colon provides a large surface area for the action

of microbes on the cellulose. Herbivores have complex stomachs

In carnivores, the digestion process is very fast and efficient. Meat has a much higher energy content

per gram than plant foods, so carnivores can eat less to gain the same amount of energy. Carnivores

digestive systems produce all the enzymes necessary to digest their food, as a result digestion is

rapid and simple.

4. Gaseous exchange and transport systems transfer chemicals through the internal and

between the external environments of plants and animals

4.1 Compare the roles of respiratory, circulatory and excretory systems

Respiratory: allows for gaseous exchange to occur

Circulatory: circulates minerals and supplies cells with nutrients; transport of gases, nutrients, waste

products; removal of toxins and pathogens; distribution of heat.

Excretory: allows for excretion of waste products

4.2 Identify and compare the gaseous exchange surfaces in an insect, a fish, a frog and a

mammal

Mammal: Lungs (internal) - large SA is increased by highly folded microstructures called alveoli, surrounded

by blood capillaries. There is a rich supply of blood to transport gases to and from the lungs.

Fish: Gills (external) - gill filaments spread out to increase SA, the rich supply of blood vessels enable gases to

and from the gills as water flows over them.

Insect: Tracheae - a system of branching tubes; branches throughout the tissues of the insects bringing air directly to the cells; movement of body forces air in and out; efficient only in a small animal due to SA:V ratio. Frog: Lungs/Skin oxygen from the air diffuses into the moist skin which is transported by the blood to the body. The lungs are simpler structures with internal subdivisions.

4.3 Explain the relationship between the requirements of cells and the need for transport

systems in multicellular organisms

Unicellular organisms have a large SA:V ratio and therefore do not need a transport system to obtain

nutrients and rid wastes.

Multicellular organisms however, have a small SA:V ratio and cannot carry out simple exchange of

nutrients and waste, cells in the organisms would then starve or be poisoned by their own waste. So,

these organisms need a series of tubes through which materials can be transported.

4.4 Outline the transport system in plants, including:

- root hair cells

- xylem

- phloem

- stomates and lenticels

Plant part Description Function

Root hair cell Consists of extension of epidermal cell to increase SA.

Provides large SA for absorption of water and mineral ions.

Xylem Long vessel with no end wall, walls strengthened with lignin, pits allow water to pass through.

Transports water from roots to leaves, doesnt require energy.

Phloem Consists of sieve tubes with sieve plate at end of tubes.

Products of Photosynthesis are transported from the leaves to the

rest of the plant.

Stomates Found in epidermis. Each pore has guard cell on either side, guard cells have chloroplasts.

Allow gaseous exchange to occur. Can close to reduce water loss by plant.

Lenticels Breaks in bark Allows gas exchange in stem for living cells behind tough bark.

4.5 Compare open and closed circulatory systems using one vertebrate and one invertebrate as

examples

Circulatory System Description Example

Closed Consists of a muscular pump that pumps fluid through a closed system of tubes which carry material throughout the body.

Highly efficient blood can be kept flowing within vessels, guaranteeing steady flow of nutrients, gases and wastes btw cells and environment

Allows vertebrates to grow very large and still function despite poor SA:V ratio of large body

Humans have a heart that pumps blood through blood vessels which carry the blood throughout the body.

Open Blood does not always stay in vessels

Body cells bathe in fluid carrying nutrients

Not efficient; blood is not forced to keep flowing

Insects rely on their tracheal system, instead of blood carrying the oxygen. Thus insects do not have to have a fast blood flow.

5. Maintenance of organisms requires growth and repair

5.1 Identify mitosis as a process of nuclear division and explain its role

Mitosis is a process of nuclear division. It is a replication and division of a cell to produce two cells

with same number of chromosomes as parent cell. Two new cells are called daughter cells, these are

genetically identical.

The role of mitosis is to make new cells when they are needed (growth, repair and reproduction). It

involves duplication of both the nucleus and nuclear material.

Stages of Mitosis:

5.2 Identify the sites of mitosis in plants, insects and mammals

Plants: mitosis occurs in tips of roots and stems; plants can replace lost parts.

Insects: mitosis occurs in each stage of metamorphosis

Mammals: mammals cannot replace lost parts; mitosis is limited to tissue repair and maintenance

(eg. Replacement of skin cells and blood cells)

5.3 Explain the need for cytokinesis in cell division

Cytokinesis is a term which means division of cytoplasm which occurs during cell division. This is

needed in cell division because the cell cytoplasm must divide to produce two new cells and keep

the cell size (and large SA:V ratio)

5.4 Identify that nuclei, mitochondria and chloroplasts contain DNA

Chromosomes are strands of DNA found in the nucleus of cells. In humans, there are 46 chromosomes or 23

pairs.

DNA on chromosomes are used to transfer information from cell to cell, thus mitochondria and chloroplast

also carry DNA. Mitochondria and chloroplasts are able to reproduce themselves in mini cell division.