water and organisms arist

7/29/2019 Water and Organisms Arist

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Water and Organisms

Water makes up between 60 - 95% of weight of

organisms


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Why is water important to

organisms?

Water is an important substance for

maintaining life. Organisms cannot livewithout water.

Water is a major cell component.


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Importance of Water It acts as:

solvent / reaction medium

medium for transport (e.g. blood) metabolite (e.g. photosynthesis)

others like act as cooling agent (e.g. sweating in

hot weather)

as supporting agent (e.g. turgidity in young plant)

for sexual reproduction


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Water as a Solvent

dissolve most organic and inorganicsubstances

needed for all biochemical reactions

remove excretory products such as ureaand excess salts

in plants, root hairs absorb mineral saltspresent in soil in solution form


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As a solvent

Inside an alveolus of the lung: O2 dissolves

in water film for diffusion

Inside a leaf : CO2 dissolves in the water

for diffusion to mesophyll cells


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Water as a Medium

of Transporthuman blood plasma consists mainly of

water (90%)

carry many dissolved substances like

excretory wastes, hormones and gases

around the body

in plants, sugar and mineral salts are

transported in solution in vascular bundles


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As a medium for transport

Human blood plasma consists mainly of

water (90%)


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Water as a Metabolite

in plants during photosynthesis,

carbohydrates are synthesized from carbon

dioxide and water

essential in hydrolytic reactions,

e.g. digestion


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As a metabolite

photosynthesis: water + carbon dioxide -->

carbohydrates + oxygen


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To provide support and to keep

shape water keeps plant cells turgid and provides a

means of support in plants


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For sexual reproduction

Sperms need water to swim to the eggs.


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Ways of Gaining Water in Animals

drinking

eating

from respiration occurs in cells which the

water formed is called metabolic water


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Ways of Losing Water in Animals

evaporation from body surfaces

sweating

exhalation

urination

defaecation


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Ways of losing water in plants:

Evaporation from body surface,

Transpiration.


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Hypotonic, Hypertonic andIsotonic Solutions

Hypotonic solution

- a solution has a higher water potential

than the reference solution


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Isotonic solution

- a solution has the same water potential as the

reference solution

Hypertonic solution

- solution has a lower water potential than

the reference solution


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Osmosis in cells

water will enter the cells if the surrounding

fluid is hypotonic ( of higher water potential)water will leave the cells if the surrounding

fluid is hypertonic ( of lower water potential)

No net water movementwill occur when thesurrounding fluid is isotonic ( of equal water

potential)

Water relations of organisms in

the cells


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Osmosis

The net movement of waterfrom a region of

higher water potential to a region oflower

water potential through a selectivelypermeable membrane.


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Osmosis in animal cell

Cell swellsand eventually burst

Cell shrinks

WaterConcentratedsaline solution


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In animal cells

water enter, the cells swell burst

water leaves, the cells shrink.

What will happen when water enters

and leaves cells?


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Animal Cells Response to DifferentSolutions

tissue

cells

water move inby osmosis

Cells swelland burst


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tissue

cellswater move out

by osmosiscells

shrink

Animal Cells Response to DifferentSolutions


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Investigation of the Effectsof Different Salt

Concentrations on

Red Blood Cells


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In A to E 5 test tubes, transfer a drop of the blood

sample and different concentrations of sodiumchloride solution to each of the test tubes.

Tube A: 0.2% sodium chloride solution

Tube B: 0.6% sodium chloride solutionTube C: 0.8% sodium chloride solution

Tube D: 1.6% sodium chloride solution

Tube E: 3.2% sodium chloride solution


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Withdraw a drop of liquid from each tube and examine it

under the microscope.


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Which of the five saline solutions most closely resemblesthe blood plasma in salt concentration ?

Ans: The one in 0.8% saline solution is the most resembles

the blood plasma concentration.

red blood cell swells

and is about to burst

red blood cell

shrinks

red blood cell remains

unchanged in appearance

In hypotonic

saline solution

In hypertonic

saline solution

In isotonic

saline solution


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What evidence supports your answer ?Ans: Red blood cells in 0.8% saline solution remain

unchanged in appearance indicating that the solution

is isotonic to blood plasma



red blood cell

shrinks



In hypotonic

saline solution

In hypertonic

saline solution

In isotonic

saline solution


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What evidence supports your answer ?Ans: Fewer red blood cells can be observed in 0.6% saline

solution and even fewer in 0.2% saline solution. This

shows the two solution are hypotonic to the red blood

cells



red blood cell

shrinks



In hypotonic

saline solution

In hypertonic

saline solution

In isotonic

saline solution


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What evidence supports your answer ?Ans: The 1.6% and 3.2% saline solutions are hypertonic to

the red blood cells as a net movement of water out of

the red blood cells into the saline solution is noticed.



red blood cell

shrinks



In hypotonic

saline solution

In hypertonic

saline solution

In isotonic

saline solution


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Importance of

Osmoregulation osmoregulation is the maintenance of correct

levels of water in the body

any excessive gain or loss of water will upset the

proper functioning of cells in an organism

metabolic reactions are affected and organisms

may die


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The importance ofosmoregulation for animal cells

Osmoregulation: The process of regulating

body fluid to keep itat a constant

concentration.

In mammals, osmoregulation is achieved by

controlling the amount of water and theamount of dissolved substances in the blood.

The major organ responsible are the kidneys


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The kidneys role in osmoregulation


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Human Urinary System

kidney

ureter

urinarybladder

urethra


35/132Human Urinary System

aorta

renal

artery

uretersurinary

bladder

leftkidney

renalvein

rightkidney

sphincter

muscle

urethra

Inferiorvena cava


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- Location of Kidneysmammals have two kidneys which are reddish

and bean-shaped

they are situated at one on each side of the

vertebral column, below the ribs and are not

protected by any part of the skeletal system renal artery brings blood to kidney while renal

vein takes blood away from it


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- Uretercarries urine from kidney down to urinarybladder where stores urine temporarily

valves are present in ureter to prevent urine from

flowing upwards

back flow of urine may happen when urinarybladder empties if valves do not close

properly.This may lead to infection and damage

of kidney


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- Urinary Bladder

a muscular bag situated towards the bottom

of the abdominal cavity

urethra is led out from it

on the top of urethra is surrounded by ring of

sphincter muscle


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Urination

normally, the sphincter muscle is tightlycontracted, so no urination occurs

when urinary bladder is full

sphincter muscle relaxes

+wall of urinary bladder contracts

urination occurs

Adults can control

the sphincter

muscle but children

cannot, it relaxesautomatically when

the bladder is full


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Structure of

Mammalian Kidneycortex

medulla

renal artery

renal vein

ureterpelvis

nephron


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Structure of

Mammalian Kidney made up of three parts:

-a light outer region - cortex- a dark inner region - medulla

- a whitish central region leads to ureter - pelvis

contain numerous tiny tubules called nephrons


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Structure of Nephron consists of a swollen end called Bowmans

capsulewhich is connected

to a narrow tubulethe tubule begins in cortex

after leaving the capsule, it coils up

(proximal convoluted tubule)


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It is then descends into the medulla and becomesU-shaped (loop of Henle)

It goes back into the cortex and coils up again

(distal convoluted tubule)

Finally, it drains into a collecting duct which goes

through the medulla and down to pelvis


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Nephron

renal artery

renal vein

proximalconvoluted tubule

(first convolution)capillaries

around nephron

Loop of

Henle

afferent

arteriole

glomerulus

efferent

arteriole

collectingduct

distal convolutedtubule (second

convolution)


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How Nephron is Connectedwith Blood Vessel

renal artery

enters Bowmans

capsuleGlomerulus (a tightly bunched

group of capillaries)

afferent arteriole(branches from renal artery)

efferent arteriole

(capillaries join up)


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How Nephron is Connected

with Blood Vesselleaves Bowmans

capsule

capillaries (spread out

and wrap around tubule)

venule(capillaries join up)

renal vein


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Bowmans capsule

(with glomerulus)

afferent arteriole

efferent arteriole

loop of Henle

Structure of

Nephron

collecting duct

first & second

convolution

venule


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How Nephron Works ?

By two ways, one is ultrafiltration

and the other is reabsorption


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Capillaries

It is the smallest blood vesselsIt is the site of exchange (by diffusion)

Diffusion

Thin wall (one cell)

CO2Waste

Nutrients

O2


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Ultrafiltration

diameter of tiny artery leading to theglomerulus is larger than the leaving one so

increase in pressure is resulted as blood

tries to force its way out of the smaller tube

the high hydrostatic pressure forces small

molecules through the walls of capillaries

and Bowmans capsule into the capsular

space


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fluid which filtered into the nephron is

glomerular filtrate

glomerular filtrate has the same composition as

that of blood except that it hasnt got red blood

cells, blood proteins & blood platelets


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Reabsorption

reabsorption is the process of absorbing

useful substances into capillaries which

wrapped around tubule

as in glomerular filtrate, some substances

like glucose and amino acid are useful to

human so they are absorbed back while fluid

travels along the tubule


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those urea which remains in the fluid pass the

whole nephron and finally drains into

collecting duct which leads to pelvis and form

urine

urine contains mostly water, with urea and

excess mineral salts


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reabsorption of glucose, amino acids and some

salts begins in the first convolution and finished

when the fluid reaches loop of Henle


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useful substances are reabsorbed by diffusion

down the concentration gradient and active

transport against concentration gradient

in collecting duct, water is mainly reabsorbed

by osmosis but the first convolution actually

reabsorbs the largest amount of water


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Functions of Kidneykidney mainly has three functions:

osmoregulation

removal of excess salt

excretion


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Functions of Kidney

- Osmoregulationdrink a lot of water

blood becomes diluted

More dilute urine

produce

small proportion of water

is reabsorbed

Amount of water in blood: CONSTANT


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after sweating

blood becomes concentrated

large proportion of water

is reabsorbed

Less concentrate urine

produce

Amount of water in blood: CONSTANT

Functions of Kidney

- Osmoregulation


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Functions of Kidney

- Removal of Excess Saltafter eating a salty meal

salt enters blood,

concentration of salt in

blood increase

volume of

urine increase

concentration of

urine is higher

man feels thirsty drink water


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Functions of Kidney

- Excretion protein cannot be stored in human body,

excess protein are broken down in liver

removing of amino groups from amino acids

is called deamination

amino groups are incorporated into urea

molecules and then excreted in urine


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Kidney Failure and

Artificial Kidney

some kidney diseases can lead to kidney

failure which kidney can no longer function

properly

toxic substances will accumulate in blood

and patient will die


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artificial kidney is a bulky machine attachedto patient which is used to filter and clean

patients blood

artificial kidney make use of the principle of

dialysis. It has a filter made of cellophane

which acts as a selectively permeable

membrane


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along one side of the membrane is the

patients blood while the other side is dialysis

fluid which has the same contain as plasma

except urea

only urea diffuses from patients blood into

dialysis fluid through cellophane filter

blood without urea will return to patient

through his vein


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dialysis fluid flows in direction opposite tothat of blood flow to increase the efficiency of

diffusion of urea into dialysis fluid

other than using artificial kidney, kidney

transplant is another possible method but

only few people are willing to donate their

kidneys after death


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Excretion in Human metabolism are reactions take place inside

cells of an organism

most of the by-products of metabolism aretoxic and should be removed once they are

produced by excretion

there are four major excretory organs in

human body: Lungs,Kidneys,Liver and Skin


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Excretory Organs - Lungs

excrete carbon dioxide which is produced bycells during respiration and is carried by

blood to lungs

carbon dioxide diffuses out of the blood

capillaries surrounding the lungs and passes

into the air sac

it is excreted when people breathe out. Water

is lost during respiration, too


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Excretory Organs - Kidneys

deamination (break down of excess amino

acids) in liver forms urea and uric acid

urea and uric acid are called nitrogenous

wastes

the wastes are carried by blood to kidneys

which excrete them from the body in form of

urine


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Excretory Organs - Liver

old red blood cells are destroyed in liver

and haemoglobin are released

haemoglobin will turned into bile and

excreted with bile into small intestine

finally, haemoglobin will expel with faeces

and leave the body


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Excretory Organs - Skin skin is the largest excretory organ in

human body

it carries out its function through

sweating

sweat contains water, salts and urea, andsweating can excrete these substances

from the body


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Plants Cell

cell wall

cytoplasm

cellmembrane

vacuole


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cell wall

freely permeable so it lets most

of molecules to go through

osmosis does not occur

cell membrane

beneath cell wall

selectively permeable


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Water Relations of Plant

- Turgorplant cell put in distilled water

plant cell

contains solutes

water potential lower

than pure water

net water movement into the cell by osmosis

vacuole and cytoplasm swells


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cell wall is rigid and strong,

cell bursting is prevented

turgor is present because:

turgor

hydrostatic pressure

develops inside the cell

cytoplasm is pushed against cell wall


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tendency of the cell to giveout water increases

water potential increases

Whenwater potential of cell

= water potential of waterTurgor occur (cell cannot take in

any water) the cell is turgid

W R l i f Pl


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Water Relations of Plant

- Plasmolysisplant cell inconcentrated solution

net water movement out

of the cell by osmosis

vacuole and

cytoplasm shrink

cytoplasm is torn away

from cell wall

flaccid

The whole phenomenon

is called plasmolysis and

cell is plasmolysed


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Plasmolysed cells

T idi f Pl C ll


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Turgidity of Plant Cells

turgid cell

(in hypotonic sol.)

plasmolysed cell

(in hypertonic sol)

cell wall

cytoplasm

vacuole

enlarged

solution here is the same

as the external solution

cell membrane separated

from cell wall vacuole

very small


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In plant cells

water enter, the cells become turgid.

water leaves, the cells become less turgid

flaccid plasmolyzed

What will happen when water enters and

leaves cells?


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Cells in Different Solutions

Solution Concentration

animal cells

(e.g. RBC)

plant cells

hypotonic hypertonic

haemolysis

turgid

shrink

plasmolysis

(cell is flaccid)


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To Investigate the Effects ofSucrose Solution and Tap Water

on Epidermal Cells of Red OnionScale Leaf or Rhoeo Discolor

Leaf


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fleshy scale leaf of

red onion bulbforceps

filter paper

epidermis

What do you observe when the epidermal strip is

placed in the concentrated sucrose solution ?

Ans:The coloured cytoplasm shrinks.


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Plasmolysis of red onion epidermal cells (400X)


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Explain your observation.

Ans:When the piece of epidermis is placed inconcentrated solution, cells lose water by osmosis

as the cells have a higher water potential than the

sugar solution.



filter paper

epidermis


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What has happened to the cells in tap water ?

Ans:The coloured cytoplasm swells and cells become

turgid.



filter paper

epidermis


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Fully turgid red onion epidermal cells (400X)


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Explain your answer.

Ans:When the piece of epidermis is placed in tap water,cells gain water by osmosis as the surrounding tap

water has a higher water potential than the cells.



filter paper

epidermis


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Effects of ConcentratedSucrose Solution and Tap

Water on Raw Potato Strips


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What has happened to the potato strips ?

Ans:Potato strip A increases in both weight and length

while potato strip B decreases in both weight and

length.

petri dish

water20% surcose solution

raw potato

strips

A B


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Ans:For potato strip A, it gains water by osmosis so both ofits weight and length increase but for potato strip B, it

loses water by osmosis so its weight and length

decrease.

petri dish

water20% surcose solution

raw potato

strips

A B


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Experiment to Show that

Water is Given Off DuringTranspiration


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What do you observe in the polythene bags ?

Ans:The one enclosing plant A becomes misty while

nothing can be noticed in the one enclosing plant B.

polythene

bag

A B


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How can you show that it is water ?

Ans:We can use anhydrous cobalt chloride paper to test it.It will turn the paper from blue to pink or we can use

anhydrous copper sulphate. Water will turn it from

white to blue.

polythene

bag

A B


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What conclusions can you draw from the results ?

Ans:We can conclude that a leafy shoot gives off waterduring transpiration.

polythene

bag

A B


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Transpiration

an evaporation of water in form of water

vapour from the surface of plant to

atmosphere


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more water loses from the lower surface of

the leaf than the upper one as more

stomata present on the lower surface

it also happens in lenticels and cuticle

it mainly takes place in leaves where there

are some openings called stomata

How does transpiration take


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How does transpiration take

place?

How water lost from leaves causes transpiration and how the

transpiration pull is formed.

How transpiration occurs

1. Water evaporates into

sub-stomatal air space

2. Water diffuses out

through stoma

How transpiration pull is

formed

1. Water is lost from the cell

surface, this is replaced by water in

the cell. Each cell then pulls water

from its neighbouring cells

( through cell wall

through cytoplasm

and vacuoles)

2. Eventually, water is pulled

from the xylem, pulling water

up the plant.

Substomatal air space with

higher concentration of water

Lower concentration of

water vapour


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water potential of cells losing water

decreases so they draw water from deeper

cells in the leaf by osmosis. This in turn,

draws water in xylem vessels into leaf to

replace the loss


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To Measure the Rate of

Transpiration by Using aSimple Potometer


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What are the environmental conditions under whichtranspiration occurs quickly ?

Ans:It is under dry, warm and windy conditions.

air/water

meniscus

graduated

capillary tube

reservoir

leafy shoot

tap


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Does this apparatus give you an accurate measurement ofthe rate of transpiration ?

Ans:No. It is because it only measures the rate of water

uptake by the leafy shoot

Ans:In addition, it is too small to fit the whole root system

and this may affect the rate of water uptake.

air/water

meniscus

graduated

capillary tube

reservoir

leafy shoot

tap


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Sometimes you may introduce an air bubble into thecapillary tube. State the advantage of this method.

Ans:Movement of the air bubble is easier to observe

than that of air/water meniscus.

air/water

meniscus

graduated

capillary tube

reservoir

leafy shoot

tap


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Sometimes you may introduce an air bubble into thecapillary tube. State the disadvantage of this method.

Ans:Friction between the capillary wall and the bubble

may affect the movement of bubble.

air/water

meniscus

graduated

capillary tube

reservoir

leafy shoot

tap


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Environmental Factors Affectingthe Rate of Transpiration

There are five environmental factors which affect

the rate of transpiration. They are:

(I) Light Intensity

(II) Temperature

(III) Humidity

(IV) Wind Speed

(V) Water Supply


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Light Intensity stomata open in light, so plants can get

enough carbon dioxide from atmosphere forcarrying out photosynthesis

light will increase temperature so increases

the rate of transpiration


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Temperature

temperaturerelative humidity of

air outside leaf

rate of evaporationof water from

mesophyll cells

rate of diffusion of water

vapour from intercellular

space in leaf to outside


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Humidity

humidity

outside

rate of

transpiration

it makes the diffusion gradient of water

vapour from moist intercellular space of aleaf to the external atmosphere steeper


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Wind Speed & Water Supplywind blows

water vapour around

the leaf sweeps away

transpiration rate

INCREASES

lack of water

soil dries, plant wilts

and stomata close

transpiration rate

DECREASES


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Stomata

stomata are pores in the epidermis which

gaseous exchange takes place during

photosynthesis (or respiration)

find mainly in lower epidermis of

dicotyledonous leaves and stems


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Guard Cells each stoma is surrounded by

two guard cells which

possess chloroplasts

its inner wall is thicker than

outer wall

it is kidney-shaped guard cell stoma


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Distribution of Stomata

in Leavesnormal plants

mainly on the lower surface of leaves

floating plants

mainly on the upper surface

leaves may also have air sacs to keepthem afloat so they can carry out

gaseous exchange


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submerged aquatic plants

no stomata (not required since gaseous

exchange can be carried out by

diffusion through the leave surface)

no cuticle (the primary function of

cuticle is to prevent excess water

transpiration which is not present in

aquatic plants)


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Experiment to InvestigateStomatal Distribution in a

Leaf by Using CobaltChloride Paper


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cobalt chloride paper

sellotape

Obtain a potted plant. Using sellotape stick a small square

of anhydrous cobalt chloride paper onto each surface of

a leaf of the plant. Record the time taken for the cobalt

chloride paper on each surface of the leaf to turn pink.


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Which piece of cobalt chloride paper turns pink first?Ans:The piece of cobalt chloride paper attached to the

lower epidermis of the leaf turns pink first.


sellotape


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Ans:It is because more stomata are present in the lower

epidermis.


sellotape


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Why is it important to handle cobalt chloride paper with

forceps?Ans:It is because there is moisture on human fingers so

the paper may turn pink before sticking onto the

surfaces of leaves


sellotape


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To Observe the Release of

Air Bubbles from Leavesplaced in Hot Water


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Where does the air come from?Ans:It is in the air spaces between the mesophyll cells

in leaf which expands on heating and passes out

through stomata of the leaf.

forceps

hot water

leaf


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What does the result show?Ans:The result shows that more stomata are present on

the lower epidermis of the leaf.

forceps

hot water

leaf


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Structure of Root

Structure of Root


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Structure of Root

Root Capa protective layer at the very tip of root

to protect the delicate cells of root from

being damaged as the root grows down

through the soil

Epidermis

cover the rest of root

absence of cuticle so water can enter


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Growing Point

behind root cap

cells are capable of active division

Region of Elongation

more elongated than cells in growing pointand have large vacuoles

Region of Root Hair


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Region of Root Hair

little way behind root tiproot hair are thin-walled extension of

epidermal cells of root

increase surface area for uptake of water

and mineral salts


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Vascular Tissue

further from the tip of root

contain xylem and phloem

xylem transport absorbed water to every

part of plant


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Absorption of Soil Water

by Root Hairs

soil water is a dilute solution of salts which

is more dilute than cell sap and cytoplasm in

root hair

water will pass by osmosis into root hair

through cell wall and cell membrane

Transverse Transport


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p

of Water to Xylem

epidermal cells

gain water by

osmosis

NOTE: some water may travel

inwards along or

between cell wallswithout entering

cytoplasm or vacuole

of each cortical cell

cytoplasm and cell

sap have higher

water potential

than neighbouringcortical cells

water travels by

osmosis inwards

from cell to cell


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transpiration occurs in leaves so water

is continuously removed from the plant

flow of water through plant: transpiration stream

tension produced to draw up water:

transpiration pull

reduction of effective pressure at the top

of xylem vessel

water flows upwards from roots continuously


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~ End ~

water and organisms arist

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