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Transcript of 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 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: 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 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: 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 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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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
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aorta
renal
artery
uretersurinary
bladder
leftkidney
renalvein
rightkidney
sphincter
muscle
urethra
Inferiorvena cava
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Human Urinary System
- 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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Human Urinary System
- 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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Human Urinary System
- 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.
fleshy scale leaf of
red onion bulbforceps
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.
fleshy scale leaf of
red onion bulbforceps
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.
fleshy scale leaf of
red onion bulbforceps
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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Explain your answer.
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.
cobalt chloride paper
sellotape
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Explain your answer.
Ans:It is because more stomata are present in the lower
epidermis.
cobalt chloride paper
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
cobalt chloride paper
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 ~