Download 04 - SCERT Kerala

BIOLOGY
You know that
the carbohydrate and
lipids of the food we take
in are converted to
carbondioxide and water at
the end of metabolism
liberating energy, and it is
this energy that is utilized
for life activities and
growth....
Didn't you notice Ammu's doubt? Didn't
you also have this doubt?
What may happen to the proteins in our
food?
Biology
Std. X
Sir, then what
happens to the
proteins in our
food?
Analyse the given description, form
inferences about this and record it in the
Science diary.
Synthesis of Urea
Aminoacids are formed due to the breakdown of proteins. These aminoacids are utilized
for the synthesis of new proteins necessary for body building, enzymes and many other
substances. During these reactions, many byproducts are formed. Many of these are
waste materials which are harmful to the body. Ammonia is a major waste product formed
in this way. It is very much harmful to the body. The ammonia formed in the cells diffuses
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BIOLOGY
into the blood and the blood carries it to the liver. In the liver, with the help of enzymes,
it combines with CO2 and water, and is converted to a substance called urea.
NH3+ CO2+H2O → Urea
The formation of urea, known as Urea cycle, takes place in a cyclic manner in several
steps. Urea is a relatively less toxic substance which is highly soluble in water. Urea
formed in the liver is transferred to blood from where it is eliminated through urine.
Like urea, other byproducts of
metabolism such as carbondioxide, water,
etc., also, in excess in the body adversely
affect homeostasis. These are to be
removed from the body to avoid such a
situation. How are carbondioxide and
water removed from the body? List the
organs which facilitate this.
Planning
Aim
..................................................................
Materials required
..................................................................
Procedure
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—
Skin
—
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Observation
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—
Urine, the main excretory material in the
body, contains mainly water, urea and
salts.
Let us plan an experiment to test the
presence of urea in urine.
Using the given description conduct an
experiment with your friends, and record
the findings in the Science diary.
Experiment
Add 2 or 3 drops of phenolphthalein to 5
ml of urine. Observe the colour change.
Add the enzyme urease into this. Observe
the colour change again.
Inference
..................................................................
..................................................................
Indication
Phenolphthalein + Urea → milk colour
Urea + Urease → Red colour
How is urine formed from blood?
Which is the organ that helps this ?
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BIOLOGY
Analysing the given description and Figure 4.1, prepare notes on the structure, position,
size, etc., of this organ.
.....................................................................................................................
Kidneys
Kidneys are the organs which purify blood by eliminating impurities in the form of urine.
There is a pair of kidneys in human beings. They are seen against the posterior muscles
of the abdominal cavity in the lumbar region, on either side of the vertebral column.
They are bean-shaped and are about 11cm long, 5cm broad and 3 cm thick. Each
kidney is dark red in colour and weighs about 150g and is covered by a rigid but soft
membrane. Blood reaches the kidneys from the heart at high pressure, through the
renal artery and returns through the renal vein. About 1100mL. of blood passes through
the kidneys per minute.
Urea, salts, excess amount of medicines taken into the body, vitamins and other harmful
substances that reach the body are filtered and removed from the blood by the kidneys.
thoracic cavity
adrenal gland
kidney
vertebral column
abdominal cavity
ureter
urinary bladder
urethra
Fig - 4.1. Kidneys and associated parts
In order to know how kidneys filter and remove impurities from blood, their internal
structure is to be understood. Analyse Fig. 4.2, complete the given illustration and
present it in the class room.
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BIOLOGY
Cortex
Renal artery
The outer part where lakhs of
micro filters are seen
The vessel which carries
blood to the kidney
Renal vein
Medulla
The vessel which carries blood
from the kidney
The inner part where long
tubes of the filters are seen
Pelvis
The part to which urine flows
from the filters
Pyramid
The part to which the collecting
ducts of micro filters open
Ureter
Fig - 4.2. Longitudinal section of kidney
Functions
The vessel which carries urine
from the kidney to the urinary
bladder
Position, size, shape
$
$
Kidneys
Internal structure,
main parts
$
Major blood vessels and their
functions
$
Each kidney has about twelve lakhs of micro filters inside. These are the nephrons.
Nephrons are the basic functional units of kidney. Analysing Figure 4.3, draw inferences
about how nephrons are arranged inside the kidney.
Fig - 4.3. The arrangement of nephrons in the kidney
nephron
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BIOLOGY
Ultrafiltration
How might kidneys be filtering out the excretory wastes in the blood? What might be
the adaptations facilitating this ? Using the indicators, analyse Figures 4.4 and 4.5.
Glomerulus
Bowman's capsule
Inside the kidney the renal
artery breaks up into minute
capillary networks which look
like a bundle of threads. Each
bundle is called glomerulus.
Minute pores are present on
its walls which effect ultra
filtration.
Bowman’s capsule is a
double-walled cuplike
covering surrounding
the glomerulus. Helps
to collect glomerular
filtrate formed as a
result of ultra filtration.
Renal tubule
The vessel connecting the
Bowman’s capsule and the
collecting duct. The reabsorption
of essential substances and
elimination of certain waste
materials take place.
Collecting duct
Urine
Fig - 4.4. Structure of a nephron
afferent vessel
efferent vessel
Glomerular filtrate
Contains water, glucose, amino acids, ions of
Sodium, Potassium and Calcium, vitamins,
urea, uric acid, creatinine, etc.
Fig - 4.5. Ultrafiltration
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Urine is collected from
the nephron. It opens
out into the pelvis.
BIOLOGY
Indicators
—
Is there any difference in size between
afferent and efferent vessels? How
does this difference affect the flow of
blood?
—
What is the advantage of the breaking
up of the afferent vessel into very
minute capillaries inside the Bowman’s
capsule?
—
Will there be any difference in the
pressure of blood in the glomerulus in
relation to the afferent and efferent
vessels? If yes, what is the reason?
—
What is the necessity of micropores on
the capillary wall?
You have observed the picture of ultra
filtration and the components of the
glomerular filtrate.
—
What are the components of the
glomerular filtrate?
—
What may be the reason for the absence
of RBC and protein in the glomerular
filtrate?
Now you have learnt the composition of
the glomerular filtrate. About 127 mL of
glomerular filtrate is formed per minute.
If the whole of the glomerular filtrate is
transformed into urine, a person would
have to expel about 180 litres of urine per
day. Does this happen? How much urine
does an individual expel in a day, on an
average?
Record your guess.
.....................................................................
filterate including water and glucose are
essential for the body. While glomerular
filtrate flows through the renal tubule,
these components are reabsorbed at
different parts of the tubule. Along with
this, certain substances which are not
useful to the body are discharged into the
glomerular filtrate. Around 126 mL of
glomerular filtrate is reabsorbed and the
remaining portion becomes urine. This
reaches the ureter through the collecting
duct. Subsequently, it is stored
temporarily in the urinary bladder
situated at the lower part of the abdominal
cavity. As and when the bladder fills, the
urge to urinate occurs and urine is
expelled through the urethra.
Components of Urine
You know that urine contains water, urea
etc.
What are the other components of urine?
Water
96%
Urea
2%
Salts and other substances
NaCl, KCl, Creatinine,
Uric acid,
Salts of Phosphorus,
Calcium, etc.
}
2%
The pale yellow colour of urine is due to the
pigment called urochrome formed as a result
of the break down of haemoglobin.
Is it now clear that all of the glomerular
filtrate is not converted to urine? What
happens to the remaining glomerular
filterate?
You have learnt that human beings excrete
on an average 1.5 litres of urine per day.
Is there any difference in this quantity due
to the changes in climate? If so, what may
be the reason?
Many components of the glomerular
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BIOLOGY
Observe Illustration 4.1., analyse the conditions causing changes in the quantity of
urine, and the mechanisms which make this possible and form inferences.
.....................................................................................................................
Rainy
season/
winter
Summer
Secretion of
ADH decreases
Secretion of
ADH increases
Quantity of
urine
increases
Quantity of
urine
decreases
Illustration - 4.1.
When kidneys fail
Unhealthy habits and life style influence the health of kidneys to a great extent. Kidneys
may fail due to several reasons and life itself may be in danger.
Read the details given in Table 4.1., gather more information and prepare a pamphlet
on diseases of the kidneys, their symptoms, reasons, etc.
Disease
Nephritis
Chronic renal failure
Kidney stone
Major Symptoms
Reasons
Dark coloured and turbid urine,
backpain and fever, swelling of the
face, ankles and feet.
Streptococcus infection, infection of
urinary bladder, Autoimmune
deficiency syndrome, etc.
Anaemia, weight loss, giddiness,
vomiting, etc.
Urea and other excretory wastes are
not filtered out, but retained in the
blood itself.
Various types of renal diseases,
diabetes, hypertension, etc.
Pain in the lower abdomen, urinary
block, backpain, giddiness and
vomiting.
Calcium oxalate, calcium
phosphate etc., get sedimented in
the kidney and ureter as grains.
Table - 4.1
Is there any means to sustain life of an
individual whose kidneys fail to function?
Have you heard of dialysis?
What is dialysis?
It is the process of purification of the blood
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by filtering out impurities from it using
complex machinery. Dialysis is conducted
when both the kidneys fail. Observe
Illustration 4.2 and identify the stages of
dialysis and record it in the Science diary.
BIOLOGY
2. The chemical substance called
heparin is mixed with blood to prevent
coagulation
1. The blood containing high amount
of excretory wastes is collected from
the artery
3. Artificial kidney (filters the blood
and separates excretory wastes )
Dialysing
fluid
4. Purified blood is passed
back to vein
Illustration - 4.2. Dialysis
Kidney Transplantation
Given below are the contents of a poster pasted on the wall of a Primary Health Centre.
Using this, discuss the significance and limitations of kidney donation and record the
details in the Science diary. Collect more information and pictures of kidney donation
and display them on the bulletin board.
Donate kidneys...... Share life......
•
Kidney transplantation becomes necessary in a condition in which both
the kidneys completely fail beyond treatment.
•
The kidney of a healthy individual who dies in an accident (deceased
donor) or that of a healthy person (living donor) can be donated.
•
Whatever be the category of donor, the blood groups of the donor and
the recipient must be compatible.
•
It is a functional kidney that is transplanted from the donor to the
recipient. Kidney transplantation is successful only when the recipient’s
body completely accepts the kidney.
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BIOLOGY
Other Excretory Organs in the Body
You have learnt that the lungs, liver and skin are the other organs which eliminate
excretory materials formed in the body. What are the wastes that they expel? How do
they function? Analyse the figures and notes given below ( 4.6 to 4.8) and complete
Table 4.2.
The carbon dioxide formed
as a result of metabolic
activities is collected and
expelled from the body
along with water vapour.
Fig - 4.6
Lungs
The waste management
plant that maintains
homeostasis by detoxifying
most of the toxins that
reach the blood. Liver does
not directly eliminate
excretory materials.
Fig - 4.7
Liver
Excretory Organs
Fig - 4.8
The sweat glands in the skin expel
water and wastes like urea and uric
acid through sweat. Sweat contains
99% water and 1% salts and other
substances.
Skin
Organ
Excretory Materials
Method of Elimination
Table - 4.2.
Like human beings, other animals also have systems to remove wastes formed as
metabolic byproducts. But depending on the peculiarities of the circumstances in which
they live, they are diverse in structure. Analyse the given description and compare the
excretory organs, excretory materials, mechanisms of excretion, etc., of other organisms.
Find out the similarities and differences, and the main reasons thereof and record them
in the Science diary.
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BIOLOGY
Excretion in Other Organisms
Amoeba
contractile vacuole
Fig - 4.9.
There are no excretory organs in amoeba which is a unicellular
organism. But this function is performed with the help of contractile
vacuoles. Excess water that reaches the body is also expelled
through the contractile vacuole.
Earthworm
Fig - 4.10.
Nephridia
Nephridia are the excretory organs in earthworm.
They separate water, nitrogenous wastes, etc.,
from the body cavity and expel them through the
pores on the body surface.
Insects
Fig - 4.11.
The excretory organs of insects are known as
Malpighian tubules. They are minute tubes
spread out in the body fluid that fills the body
cavity and open out into the alimentary canal.
Malpighian tubules separate impurities from the
body fluid and carry them to the alimentary canal,
from where they are expelled.
Malpighian tubule
Fish
The major excretory material in fish is ammonia, which is
excreted directly into water through the kidneys.
Fig - 4.12.
Frog
Nn{Xw
4.13
Fig - 4.13.
Kidneys are the organs of excretion in frogs too. In tadpoles which
are fully aquatic, ammonia is the excretory material. But when tadpole
metamorphose into frog, instead of ammonia, urea is eliminated as
the excretory material.
Reptiles and Birds
Fig - 4.14.
Uric acid is the excretory material in birds
and reptiles. It is solid or semisolid in form
and insoluble in water. This minimises the
loss of water through excretion. Kidneys
are the excretory organs in them too.
Fig - 4.15.
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BIOLOGY
Do Plants Excrete ?
Did you notice the question? Read the description given below, observe the plants
around you carefully, discuss the findings with friends, and present them in the class.
Excretion in Plants
In plants too there are mechanisms to eliminate excretory materials formed as a result of
metabolic reactions. In plants there is no specific excretory system as in animals. The
quantity of wastes formed in plants is also very low compared to that in animals. The
main reason for this is said to be the lesser rate of activity in plants when compared to
animals. The excess oxygen produced as a byproduct of photosynthesis is eliminated
through stomata. Carbon dioxide formed as a result of cell respiration is also expelled
through the stomata.
From the soil plants absorb more water than required. This excess water is expelled
through stomata and hydathodes. Hydathodes are minute pores at the tip of the leaves
of plants of the grass species to eliminate water. Water is expelled as vapour through the
stomata, and as droplets through the hydathode.
Certain excretory products reach the older xylem vessels in the stem and accumulate
there. This activity has a significant role in the gradual formation of heart wood.
Shedding of leaves is another mechanism for the elimination of excretory products in
plants. Plants reabsorb the essential components from leaves as they ripen and fall.
Therefore in the falling leaves, excretory materials will be the major content.
You have learnt that in order to maintain homeostasis, organisms keep the internal
environment free of wastes. If so, shouldn’t we conserve our external environment for
the wellbeing of nature and its countless species of living beings? Observe Figure 4.16.
Fig - 4.16.
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BIOLOGY
Have you come across such heaps of
waste?
—
What impacts do this bring about?
—
Enlist them.
—
—
Shouldn’t we put an end to such
pollution? How?
—
Does your school premises get dirty like
this?
If so, by what all means does it get dirty?
Enlist them.
The leftover of lunch, packing leaves
etc.
By group activity, form an action plan to
eliminate such heaps of waste . After
presenting it in the class room, implement
it collectively for the welfare of the public.
Be a model to society.
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BIOLOGY
Follow up Activities
1. Observe the figure.
A
B
a. Label the parts termed A and B.
b. What difference has occurred in the structure of A and B?
c. How will this affect the function of the kidneys?
2. Given below is the last part of the pamphlet about kidney diseases, prepared by
Sajin.
Our health habits and life style, to a great extent, influence the health of the
kidneys. And due to many reasons, the kidneys are damaged, sometimes even
endangering life itself. By taking necessary precautions, the kidneys can be
retained healthy to a certain extent.
Suggest any four precautions and complete the pamphlet
3. Prepare 2 slogans for the awareness rally organized by the Environment Club of
your school as part of the waste disposal scheme.
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