LIFE
PROCESS
Very
Short Answer Type Question
Q.
Mention the raw materials required for photosynthesis.
Solution: The following raw materials are required for photosynthesis:
(i)
Carbon Dioxide: Plants get CO2 from the atmosphere through stomata.
(ii)Water:
Plants absorb water from the soil through roots and transport to leaves.
(iii)
Sunlight: Sunlight, which is absorbed by the chlorophyll and other green parts
of the plant.
Q.
What would be the consequences of deficiency of haemoglobin in your body?
Solution: The deficiency of haemoglobin in our body is called anaemia. In anaemia,
the blood is unable to carry a sufficient amount of oxygen required by the
body. So, respiration would be less and less energy will be available to the
body. The haemoglobin deficient person will feel weak, pale, lethargic and will
be unable to perform heavy physical work.
Q.
Name the green dot-like structures in some cells observed by a student when a
leaf peel was viewed under a microscope. What is this green colour due to?
Solution: The green dot-like structures in some cells observed by a student
when a leaf peel is viewed under a microscope are chloroplasts. The green
colour is due to the presence of green pigment, chlorophyll.
Q.
State any one difference between autotrophic and heterotrophic modes of
nutrition.
Solution: In autotrophic nutrition, organisms obtain their food from
inorganic substances. In heterotrophic nutrition, organisms derive their food
from organic substances.
Q. Give one reason why multi-cellular organisms require special organs for the exchange of gases between their body and their environment.
Answer: In unicellular organisms, the entire body of the organism is in
contact with the environment hence exchange of materials can take place but, in
multicellular organisms, the entire body of the organism is not in contact with
the environment and hence simple diffusion is not helpful.
Q.
Name the process in plants where water is lost as water vapour.
Solution: Transpiration is the process when plants loose water as vapour.
Q.
What is‘translocation’in plants?
Solution: Translocation is the movement of soluble materials, products of
photosynthesis from leaves to other tissues throughout the plant.
Q.
State the basic difference between the process of respiration and
photosynthesis.
Solution:
Q.
Name the intermediate and the end products of glucose breakdown in aerobic respiration.
Solution:
Q.
In the experiment “Light is essential for photosynthesis”, why does the the uncovered part of the leaf turn blue-black after putting iodine solution?
Solution: Starch is produced in the uncovered part of the leaf because it is
exposed to sunlight allowing it to photosynthesize, which turns blue-black in
presence of iodine solution.
Q.
Name the component of blood that helps in the formation of a blood clot in the
event of a cut.
Solution: Platelets help in the clotting of blood in the event of a cut.
Q.
Mention how organisms like bread moulds and mushrooms obtain their food.
Solution: Organisms like bread moulds and mushrooms breakdown the food
materials outside the body and then absorb the nutrients of the bread.
Q.
What will happen to a plant if its xylem is removed?
Solution: Xylem in plant transports water and dissolved mineral nutrients
from the roots to all parts of the vascular plant. So, if xylem is removed from
the plant, the water and mineral supply to the plant will stop and therefore,
the plant will die.
Q.
Where does digestion of fat take place in our body?
Solution: Digestion of fat takes place in the small intestine of our body.
Q.
What is the mode of nutrition in human beings?
Solution: Holozoic nutrition.
Short
Answer Type Questions:
Q.
What are enzymes? Name any one enzyme of our digestive system and write its function.
Solution:
Enzymes are biological catalysts. Catalysts are proteins that
increase the rate of chemical reactions without being used up. For example:
Amylase catalyses the breakdown of starch into sugars in the mouth and small
intestine
Q.
(i) Write the balanced chemical equation for the process of photosynthesis,
(ii)
When do the desert plants take up carbon dioxide and perform photosynthesis?
Solution: (i) Photosynthesis can be represented using a chemical equation.
The overall balanced equation is
(ii) Desert plants open up their stomata during the night and take in CO2. Stomata remain close during the day time to prevent the loss of water by transpiration. They store the CO2 in their cells until the sun comes out and they can carry on with photosynthesis during the day time.
Q.
Why do herbivores have longer, small intestine than carnivores?
Solution:
Digestion of cellulose takes a longer time. Hence, herbivores
eating grass need a longer small intestine to allow complete digestion of
cellulose. Carnivorous animals cannot digest cellulose due to the absence of
enzyme CELLULASE, hence they have a shorter intestine.
Q.
Write the correct sequence of four steps of the method for the preparation of temporary
mount of a stained leaf peel.
Solution:
1.
Take a healthy leaf from the potted plant.
2.
Remove a part of the peel from the lower surface of the leaf. You can do this
by folding the leaf over and gently pulling the peel apart using forceps. Keeps
the peel in a watch glass containing water.
3.
Put a few drops of safranin stain in a watch glass.
4.
After 2-3 minutes take out the peel and place it on a clean glass slide.
5.
Put a drop of glycerin over the peel and place a clean coverslip gently over
it with the help of a needle.
6.
Remove the excess stain and glycerin with the help of blotting paper.
7.
Observe the slide under magnifications of the compound microscope.
Q.
Why do the walls of the trachea not collapse when there is less air in it?
Solution:
Rings of cartilages are present in the trachea. These rings support
the trachea and do not allow the trachea to collapse when there is less air in
it.
Q.
What are the final products after digestion of carbohydrates and proteins?
Solution:
The final product produced after digestion of carbohydrates is
glucose and of proteins is amino acids.
Q.
What is saliva? State its role in the digestion of food.
Solution:
Saliva is a watery fluid secreted by the salivary glands in the
mouth. The digestive functions of saliva include moistening food, and helping
to create a food bolus, so it can be swallowed easily. Saliva contains the
enzyme amylase that breaks some starches down into maltose and dextrin.
Q.
Explain the process of nutrition in Amoeba.
Solution:
Amoeba is an important protozoa found in freshwater. It feeds on
microscopic plants and animals present in water. The mode of nutrition in
amoeba is Holozoic. And the process of obtaining food by amoeba is called
phagocytosis. The different processes involved in the nutrition of amoeba are:
1. Ingestion: Ingestion is the process of
taking food in the body. Amoeba is a unicellular animal, so it doesn’t have a
mouth for ingestion of food. Amoeba ingests the food by encircling it by forming
pseudopodia. When the food is completely encircled, the food is engulfed in
the form of a bag called food vacuole.
2. Digestion: Digestion is the process of
breaking the large and insoluble molecules in small and water soluble
molecules. In amoeba, several digestive enzymes react on the food present in the
food vacuoles and break it down into simple and soluble molecules.
3. Absorption: The food digested by
digestive enzymes is then absorbed in the cytoplasm by the process of
diffusion. While the undigested food remains in the food vacuole. If a large
amount of food is absorbed by amoeba, the excess food is stored in the the cytoplasm in the form of glycogen and lipids.
4. Assimilation: During this step, the food
absorbed by the cytoplasm is used to obtain energy, growth and repair. This
process of utilizing absorbed food for obtaining energy, repair and growth is
called assimilation.
5. Egestion: When a sufficient amount of
undigested food gets collected in the food vacuole, it is thrown out of the body
by rupturing cell membrane. The process of removal of undigested food from the
body is called egestion.
Q.
State two differences between arteries and veins.
Solution:
Arteries:
1.
Arteries carry oxygenated blood, away from the heart except for pulmonary artery.
2.
These are thick-walled, highly muscular except arteries of the cranium and
vertebral column.
3.
Valves are absent.
4. Blood
in arteries moves with pressure.
Veins:
1.
Veins carry deoxygenated blood, towards the heart except for pulmonary veins.
2.
These are thin-walled.
3.
Valves are present which provide a unidirectional flow of blood.
4.
Blood in veins moves under very low pressure.
Q.
How are the alveoli designed to maximise the exchange of gases?
Solution:
Alveoli are small pouches or
sacs like structure. They are surrounded by blood capillaries.
Thus
a large amount of air is brought in contact with the air in the lungs. More
than millions of alveoli are present in the lungs. The presence of millions of
alveoli in the lungs provides a very large surface area for the exchange of
gases. The availability of large surface area maximises the exchange of gases.
Q.
Name two excretory products other than 02 and CO2 in plants.
Solution: The two
excretory products other than 02 and CO2 in plants are resins and gums.
Short
Answer Type Questions
Q.
In single-celled organisms, diffusion is sufficient to meet all their
requirements of food, exchange of gases or removal of wastes but it is not in
case of multicellular organisms. Explain the reason for this difference.
Solution: Unicellular
organisms can absorb sufficient oxygen because of its complete contact with the
atmosphere, but in multicellular organisms, the rate
of absorption and diffusion becomes very less because
all cells are not in direct contact with the atmosphere. Multicellular
organisms require a greater amount of oxygen to
sustain life processes which cannot be fulfilled by the process of diffusion.
Q.
Draw a diagram of the human excretory system and label kidneys, ureters on it.
Solution:
Q.
Name the acid presents in the following:
(i)
Tomato (ii) Vinegar (iii) Tamarind
Solution:
(i)
Oxalic acid (ii) citric acid (iii) Tartaric acid.
Q.
State the role of the following in the human digestive system :
(i)
Digestive enzymes (ii) Hydrochloric acid (iii) Villi
Solution:
(i) Digestive enzymes – Foods need to be
broken into their small or simpler molecules so that they can be absorbed into
the bloodstream. However, the physical breakdown of food is not enough. Enzymes
are hence needed for the chemical breakdown of food and speeding up the digestive
process. The products of digestion can hence be small enough to be absorbed.
(ii) Hydrochloric acid – Hydrochloric acid helps to kill the germs which might have entered into the system through food. It creates an acidic medium for the pepsin to act on food to breakdown proteins.
(iii)
Villi – Villi are finger-like projections in the small intestine. They help to
increase the surface area
for
absorption of the digested food. Villi are richly supplied with blood vessel
which helps to absorb digested food into the bloodstream.
Q.
In mammals and birds, why is it necessary to separate oxygenated and
de-oxygenated blood?
Solution:
Mammals
and birds are warm-blooded animals. This means they can control their body temperature
and do not have to depend on the environment for their body temperature regulation.
Because
of these birds and mammals require optimum oxidization of glucose which would be
possible with a good supply of oxygen. So it is required to have separate
oxygenated and de-oxygenated blood to supply the required amount of oxygen.
Q.
Draw a neat diagram of the excretory system of human beings and label on it:
(i)
Left kidney (ii) Urinary bladder
Solution:
Q.
Draw a diagram of the human respiratory system and label on it :
(i)
Diaphragm (ii) Larynx
Solution:
Q. (a) Name the site of exchange of material between the blood and surrounding cells.
(b) Draw a schematic representation of transport and exchange of oxygen
and carbon dioxide in the human body.
Solution:
(a)
Capillaries.
(b)
Q.
List three characteristics of lungs which make it an efficient respiratory
surface.
Solution:
These features which particularly make our lungs efficient for gas
exchange.
1. Thin: the air sac walls are very thin
so that gases can quickly diffuse through them. Oxygen is absorbed into the
blood and carbon dioxide is given out into the lungs to be exhaled out.
2. Moist: the air sacs are moist with
mucus so that gases can dissolve before diffusing.
3. Large surface area: the surface area
for gases to diffuse through in human lungs is roughly the same as a tennis
court. The alveoli help to increase the surface area for absorption of oxygen.
4. Good blood supply: the air sacs or the
alveoli have a large capillary network so that large volumes of gases can be
exchanged. More the flow of blood more exchange.
Q.
(a) What is the role of HCl in our stomach?
(b)
What is the emulsification of fats?
(c)
Which protein-digesting enzyme is present in pancreatic juice?
Solution:
(a)(i)
It sterilises food by killing pathogens and other microbes.
(ii)
It has a pH of 2, which is perfect for entyaus such as pepsin to break down
proteins as effectively as possible.
(iii)
Helps emulsify food (digestion of protein and stimulates the pancreas to
produce digestive enzymes and bile) and protects against harmful ‘bacteria’.
(b)
Breakdown of large globule fats into smaller fats droplets is known as
emulsification.
(c) Trypsin
is the enzyme secreted by the pancreas which aids in the digestion of proteins.
Q.
List in tabular form three differences between arteries and veins.
Solution:
Q.
In the human alimentary canal, name the site of the complete digestion of various components of food. Explain the process of digestion.
Solution:
In the small intestine, complete digestion of various components of
food takes place. The process of digestion of food in the mouth, stomach and small
intestine in the human body are as follows:
Mouth:
Digestion of food begins in the mouth. Saliva present in the mouth contains a
digestive enzyme, called salivary amylase, maltose and dextrins, which breaks
down starch into sugar.
Stomach:
Stomach stores and mixes the food received from the oesophagus with gastric
juices. The main components of gastric juice are hydrochloric acid, mucus and
pepsinogen. Hydrochloric acid dissolves bits of food and creates an acidic
medium. In this medium, pepsinogen is converted to pepsin which is a
protein-digesting enzyme. Mucus protects the inner lining of the stomach from
the action of HC1.
Small Intestine: Small intestine is the site of the complete digestion of carbohydrates, proteins and fats. Small intestine produces intestinal juice from the glands present in its wall. The intestinal juice helps in further digestion of food. The small intestine also obtains digestive juices from liver and pancreas. The liver produces bile juice that causes emulsification of fats and the pancreas produces pancreatic juice for digesting proteins and emulsified fats. This digested food is finally absorbed through the intestinal walls.
Q.
List the three kinds of blood vessels of the human circulatory system and write
their functions in tabular form.
Solution:
Three types of blood vessels in the human circulatory system are:
Arteries, Veins and Capillaries.
Their
functions are tabulated below:
Q.
(a) “The breathing cycle is rhythmic whereas the exchange of gases is a continuous process”.
Justify this statement.
(b)
What happens if conducting tubes of the circulatory system develops a leak? State
in brief, how could this be avoided?
(c)
How the opening and closing of stomata takes place?
Solution:
(a) The breathing cycle involves inhalation and exhalation of air
due to alternate expansion and
contraction of the thoracic cavity. Thus it is a rhythmic process. But the exchange of
gases is a continuous process as it takes
place between the blood and each and every cell, by diffusion.
(b)
The circulatory system will become inefficient if it develops a leak. This
could be avoided by maintaining normal blood pressure.
(c)
When water flows into the guard cells, the guard cells swell and the stomatal
pore opens up. When water moves out the guard cells shrinks and the stomatal
pore closes.
Q.
Draw a diagram of the front view of the human heart and label any six parts
including at least two, that are concerned with arterial blood supply to the
heart muscles.
Solution:
Q.
Describe in brief the function of kidneys, ureters, urinary bladder and urethra.
Solution:
The Kidneys filter the blood and concentrate the filtrate to make
urine. They also help regulate blood pressure.
Ureters
transport the urine to the urinary bladder.
Urinary the bladder is like a holding tank for the urine until it’s ready to be excreted. The urethra is the tube that connects the urinary bladder to the outside of the
body for excretion.
Q.
Explain the process of breakdown of glucose in a cell (ii) in the absence of
oxygen.
Solution: The process of breakdown of glucose in a cell are as follows:
The first step
in the breakdown of glucose both in presence of 02 and in absence of Os is
same. In this step, glucose is broken down into pyruvate.
Second step
which involves the further breakdown of private into simple compounds can take
place in two different ways:
(i) In the presence
of Oz: In the presence of 02, private is converted into C02 and water. The energy released
during aerobic respiration is much greater than that released during anaerobic respiration.
(ii)In the absence of Oz: In the absence of 02 in yeast, pyruvate is converted into ethanol and C02 and the process is called fermentation. In absence of 02, in our muscle cells, pyruvate is converted into lactic acid. The build up of lactic acid in muscle cells causes cramps.
Long Answer Type Question
Q. (a) Explain how does the exchange of gases occur in
plants across the surface of stems, roots and leaves.
(b) How are water and minerals transported in plants?
Solution:
(a) In plants there are tiny pores called stomata on
leaves and lenticels in the stem which facilitate the exchange of gases. Carbon
dioxide is taken in and oxygen is given out {during photosynthesis} and vice versa
during respiration.
(b) Water and minerals are transported within the
plant by the Xylem vessels (mainly in an upward direction); these are part of
the vascular system which also includes Phloem vessels.
Phloem transports the products of photosynthesis
within the plant, to all parts like the stem, roots, fruits etc. in all
directions.
Q. Draw a diagram of the human excretory system and label
renal artery and urethra.
State, in brief, the function of:
1. renal artery
2. kidney
3. ureter
4. urinary bladder
Solution:
1. Renal artery: The renal artery carries blood to the kidneys from the
abdominal aorta. This blood comes directly from the heart and is sent to the kidneys to be filtered before it passes through the rest of the body. Up to
one-third of the total cardiac output per heartbeat is sent to the renal
arteries to be filtered by the kidneys. Each kidney has one renal artery that
supplies it with blood. The filtered blood then can exit the renal vein.
2. Kidney: The kidneys perform the essential function of removing waste
products from the blood and regulating the water fluid levels. The kidneys
regulate the body’s fluid volume, mineral composition and acidity by excreting
and reabsorbing water and inorganic electrolytes.
3. Ureter: The ureter is a tube that carries urine from the kidney to
the urinary bladder.’ There are two ureters, one attached to each kidney.
4. Urinary bladder: The urinary bladder is an expandable muscular sac
that stores urine before it is excreted out of the body through the urethra.
Q. (a) Draw a diagram of the excretory system in human beings and label the
following parts.
Aorta, kidney, urinary bladder and urethra.
Solution:
Q. (a) Draw a diagram to show open stomatal pore and
label on it:
(i) guard cells
(ii) chloroplast
(b) State two functions of stomata.
(c) How do guard cells regulate the opening and
closing of stomatal pore?
Solution: (a)
(b) Two functions of stomata are:
(i) Exchange of gases between the plant and the
atmosphere takes place through stomata.
(ii)Transpiration in plants takes place through
stomata.
(c) Opening and Closing of Stomatal Pore: The opening
and closing of the pore is a function of the guard cells. The guard cells swell
when water flows into them causing the stomatal pore to open.
Similarly, the pore closes if the guard cells shrink.
As large amount of water is lost through these stomata, the plant closes these
pores when it does not require carbon dioxide for photosynthesis.
Q. (a) Draw a diagram of the human respiratory system and
label the following:
(i) the part where the air is filtered by fine hair and mucus
(ii) the part which terminates in balloon-like
structures
(iii) balloon-like structures where the exchange of gases takes place.
(iv) the part which separates the chest cavity from the abdominal
cavity.
(b) Why is the rate of breathing in aquatic organisms
much faster than in terrestrial organisms?
Solution: (a)
(b) Quantity of dissolved oxygen is fairly low in the water as compared to
the amount of oxygen in the air. Aquatic organisms, therefore, have to breath faster
than terrestrial organisms to absorb the required amount of oxygen from the
water.
Q. (a) Draw a schematic representation of transport and exchange of
oxygen and carbon dioxide during transportation of blood in human beings and
label on it:
Lung capillaries, Pulmonary artery to lungs, Aorta to the body, Pulmonary
veins from the lungs.
(b) What is the advantage of separate channels in mammals and birds for
oxygenated and
deoxygenated blood?
Solution:
(a) A schematic representation of transportation and exchange of oxygen
and carbon dioxide during transportation of blood in human beings:
(b) It is necessary to separate oxygenated and
deoxygenated blood in mammals and birds because they need high energy and a large
amount of oxygen. The separation of oxygenated and deoxygenated blood provides
high oxygen supply to the organs.
Q. (a) Draw a diagram depicting Human Alimentary Canal
and label on it: Gall bladder, Liver and Pancreas.
(b) State the roles of Liver and Pancreas.
(c) Name the organ which performs the following
functions in humans:
(i) Absorption of digested food
(ii) Absorption of water.
Solution: (a)
(b) Liver: It synthesizes and stores bile juice secreted
by gall bladder which breaks down fats into fat globules.
(c) The organ which performs the following functions
in humans are as follows:
Pancreas: It secretes pancreatic juice which contains
protein-digesting and starch- digesting enzymes. *
(i) Absorption of digested food – Small intestine.
(ii)Absorption of water – Large intestine.
Q. (a) Draw a sectional view of the human heart and
label on it – Aorta, Right ventricle and Pulmonary veins.
(b) State the functions of the following components of
transport system:
(i) Blood (ii) Lymph
Solution: (a)
(b) The functions of blood and lymph are as follows:
(i) Blood
Oxygen is transported by the blood to the tissues of the body for the breakdown of digested food.
Carbon dioxide is transported to the lungs by the blood plasma.
The digested and absorbed nutrients are transported by the blood to the tissues. Nitrogenous wastes are transported to the kidneys.
It regulates the body temperature and maintains the pH of the body tissues.
It transports various hormones from one region to another and bring about the coordination.
It maintains water balance to a constant level.
The lymphocytes produce antibodies against the invading antigens and protect from diseases.
It helps in rapid healing of wounds by forming a clot at the site of injury.
(ii) Lymph
It cleans the cellular environment.
It returns proteins and tissue fluids to the blood (drainage)
It provides a pathway for the absorption of fats and fat-soluble vitamins into the bloodstream.
It defends the body against disease.
Q. (a) Draw a labelled diagram of the respiratory system of human beings with the diaphragm at the end of expiration.
(b) List four conditions required for efficient gas
exchange in an organism.
Solution: (a)
(b) (i) A large surface area over which exchange can
take place.
(ii) A concentration gradient without which nothing
will diffuse.
(iii) A thin surface across which gases diffuse.
(iv) Warm conditions.
Q. (a) Draw a diagram to show the nutrition in Amoeba
and label the parts used for this purpose. Mention any other purpose served by
this part other than nutrition.
(b) Name the glands associated with digestion of
starch in the human digestive tract and mention their role.
(c) How is required pH maintained in the stomach and
small intestine?
Solution: (a)
Pseudopodia serves the purpose of locomotion apart
from nutrition.
(b) The salivary gland is associated with digestion of
starch in the human digestive tract. It secretes saliva which contains enzyme
salivary amylase. This enzyme converts starch into maltose (sugar).
(c) Gastric glands present on the walls of the stomach
release HC1. HC1 creates an acidic medium, which facilitates the action of the enzyme pepsin. Bile juice from liver makes the food alkaline in the small intestine
for the pancreatic enzymes to act.
Q. (a) Draw a labelled diagram of stomata. List two
functions of stomata.
(b) What are the raw materials used during
photosynthesis? Write the chemical equation for photosynthesis.
Solution: (a)
(i) Gaseous exchanges between plant and the atmosphere.
(ii) Plant loses water through stomata which helps in the movement of
minerals from the soil to leaves.
(b) Raw materials for photosynthesis: Carbon dioxide, water, chlorophyll
and sunlight are the essential raw materials for photosynthesis.
(i) Carbon dioxide is a gas, which is released into the atmosphere
during respiration. This gas is utilised by the autotrophic plants which enters
the leaf through the stomata present on its surface during the process of
photosynthesis.
(ii) Water is another requirement for photosynthesis, which is
transported upward through xylem tissues to the leaves, from where it reaches
the photosynthetic cells. This water then splits in the presence of sunlight
and chlorophyll.
(iii) Chlorophyll is a green pigment in plants, which acts as a catalyst.
It is responsible for absorption of the sun’s energy by the plant. The
chlorophyll pigments are photoreceptor molecules which play a key role in the
photosynthetic process. The different types of chlorophyll molecules are
chlorophyll a, b, c, d, e and bacteriochlorophyll; of which chlorophyll a and b
are the most common.
(iv) Light affects photosynthesis by its intensity, quality and
duration. In green light, the rate of photosynthesis is minimum, while in red
and blue lights the rate of photosynthesis is maximum.
Rate of photosynthesis is higher in plants getting average light of
10-12 hrs a day.
The the chemical equation for photosynthesis is as follows:
Q. (a) Leaves of a healthy potted plant were coated
with vaseline to block the stomata.
Will this plant remain healthy for long? State three
reasons for your answer.
(b) State any two differences between autotrophic
nutrition and heterotrophic nutrition.
Solution: (a) No, this plant will not remain healthy
for long. The plant will begin to die because
(i) Gaseous exchange will not take place.
(ii) No absorption of C02, hence no photosynthesis.
(iii) Transpiration will not occur; hence no transportation of water.
Q. (a) List the three events that occur during the
process of photosynthesis.
Explain the role of stomata in this process.
(b) Describe an experiment to show that “sunlight is
essential for photosynthesis.”
Solution:
(a) The three events that occur during the process of
photosynthesis are:
(i) Absorption of light energy by the green pigment
chlorophyll.
(ii) Conversion of light energy into chemical energy
and the splitting of the water molecule into hydrogen and oxygen.
(iii) Reduction of carbon dioxide into carbohydrate.
Role of Stomata
Stomata are tiny pores present on the surface of
leaves. They are also present on the surface of young stems. Stomata are mainly
engaged in the exchange of gases (entry of CO2 and release of O2 ) associated
with photosynthesis. The plant closes the stomata when it does not need CO2 for photosynthesis.
(b) Sunlight is essential for photosynthesis
Procedure:
(i) Place a healthy green potted plant in a dark room
for 1-2 days. This is done to ensure that the plant consumes all its reserve
food and the leaves do not contain any starch.
(ii) Then, cover a portion of a leaf of this plant on
both sides with two uniform pieces of black paper, fixed in position with two
paper clips.
(iii) Now, expose this plant to bright light. After a
few hours, remove the leaf and decolourize it with alcohol and test the presence
of food (starch) with iodine solution.
Observation: It can be observed that the portion of
the leaf, covered with black paper does not contain starch (food),
Conclusion: This is because the food prepared by
plants through the process of photosynthesis is stored as starch. Starch reacts
with the iodine solution to give blue-black colour. Only those portions of the
leaf that were exposed to sunlight could photosynthesise. Hence, gives blue-
black colour when tested with iodine. The portion of the leaf, covered with
black paper did not receive sunlight.
Hence, starch was not produced. Thus, it can be concluded
that sunlight is essential for photosynthesis.
Q. (a) What is meant by breathing? What happens to the
rate of breathing during vigorous exercise and why?
(b) Define translocation concerning transport in
plants. Why is it essential for plants?
Where in plants are the following synthesised?
(i) Sugar (iii) Hormone
Solution: (a)
The process of taking in of oxygen from the air into the lungs and expulsion of
carbon dioxide out of the lungs is called breathing. The rate of breathing
during vigorous exercise increases
by about 20 to 25 times per minute. It is because during vigorous exercise the demand for oxygen increases. Breathing occurs
involuntarily but its rate is controlled by the respiratory centre of the brain.
(b) Translocation is the transport of food from the
leaves to other parts of the plant and occurs in the part of the vascular
tissue is known as phloem. It is essential for plants because every part of the plant needs food for obtaining energy for building its parts and maintaining
its life.
(i) Sugar is synthesised in the leaves of the plant.
(ii) Hormones are synthesised at the tips of roots and
stems of a plant.
Q. (a) Draw the structure of a nephron and label the
following on it:
The glomerulus, Bowman’s capsule, Renal artery, Collecting
duct.
(b) What happens to glucose that enters the nephron
along with filtrate?
Solution: (a)
(b) During excretion in human beings, glucose which enters the nephron
along with filtrate gets reabsorbed by blood capillaries surrounding the
nephron.
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