LIFE PROCESSES
VERY SHORT ANSWER TYPE QUESTION
[1 MARK]
1. What will happen to a plant if its xylem is
removed?
Answer.
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.
2. Where does digestion of fat take place in
our body?
Answer.
Digestion of fat takes place in the small intestine of our body.
3. Name one accessory pigment and one
essential pigment in photosynthetic plants.
Answer. Accessory
pigment – Carotene/Xanthophyll Essential pigment – Chlorophyll
4. What is the mode of nutrition in human
beings? Answer. Holozoic
nutrition.
5. Mention the raw materials required for
photosynthesis.
Answer. The
following raw materials are required for photosynthesis:
(i) Carbon
Dioxide: Plants get CO2 from atmosphere through stomata.
(ii)Water: Plants absorb water from soil through roots and
transport to leaves.
(iii) Sunlight: Sunlight, which is absorbed by the
chlorophyll and other green parts of the plant.
6. What would be the consequences of
deficiency of hemoglobin in your body?
Answer.The
deficiency of hemoglobin in our body is called anemia. In anemia, the blood is
unable to carry the sufficient amount of oxygen required by the body. So,
respiration would be less and less energy will be available to the body. The
hemoglobin deficient person will feel weak, pale, lethargic and will be unable
to perform heavy physical work.
7. 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?
Answer. 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.
8. State any one difference between
autotrophic and heterotrophic modes of nutrition. Answer. In autotrophic nutrition, organisms obtain their food from
inorganic substances. In heterotrophic nutrition, organisms derive their food
from organic substances.
9. Give one reason why multicellular organisms
require special organs for 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.
10. Name the process in plants where water is
lost as water vapour. :
Answer.
Transpiration is the process when plants loose water as vapour.
11. What is‘translocation’in plants?
Answer.
Translocation is the movement of soluble materials, products of photosynthesis
from leaves to other tissues throughout the plant.
12. State the basic difference between the
process of respiration and photosynthesis. Answer. Respiration uses O2 and releases CO2
but in photosynthesis, CO2 is used and O2 is released.
13. Name the intermediate and the end products
of glucose breakdown in aerobic respiration.
Answer.
14. Mention two structural features of small
intestine which add to the absorptive capacity.
Answer. Two
structural features of small intestine are:
(i) Villi
is present to increase the absorptive surface area.
(ii) Lacteals
in the villi receive the products of fat digestion.
15. In the experiment “Light is essential for
photosynthesis”, why does the uncovered part of the leaf turn blue-black after
putting iodine solution?
Answer.
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.
16. Name the component of blood that helps in
the formation of blood clot in the event of a cut.
Answer.
Platelets help in clotting of blood in the event of a cut.
17. Mention how organisms like bread moulds and
mushrooms obtain their food.
Answer.
Organisms like bread moulds and mushrooms breakdown the food materials outside
the body and then absorb the nutrients of the bread.
18. What advantage over an aquatic organism
does a terrestrial organism have with regard to obtaining oxygen for
respiration?
Answer. The amount
of oxygen dissolved in water is very low, as compared to amount of oxygen in
air. Thus, terrestrial organism has to make less efforts to obtain oxygen than
an aquatic organism to obtain oxygen for respiration.
19. Name the two ways in which glucose is
oxidised to provide energy in various organisms. Answer. The two ways in
which glucose is oxidised to provide energy in various organisms are aerobic
respiration pathway which uses oxygen to break-down glucose completely into
carbon dioxide and water and some use other pathways that do not involve oxygen
which is called anaerobic respiration pathway.
20. Specify two conditions in which
photo-respiration may take place in green plants. Answer. Two conditions in
which photorespiration may take place in green plants are: (i) High
concentration of oxygen and (ii) High temperature
SHORT ANSWER TYPE QUESTIONS[I]
[2 MARKS]
21. What are the final products after digestion
of carbohydrates and proteins?
Answer. The
final product produced after digestion of carbohydrates is glucose and of
proteins is amino acids.
22. What is saliva? State its role in the
digestion of food.
Answer.
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.
23. Explain the process of nutrition in Amoeba.
Answer.
The mode of nutrition in Amoeba is holozoic. It feeds on unicellular plant or
animal. The various steps of nutrition are ingestion, digestion, assimilation
and egestion. When Amoeba comes in contact with food particles, it sends out
pseudopodia, which engulfs the prey by forming a food cup, which is known as
ingestion. When the tips of the encircling pseudopodia touch each other, the
food is encaptured into a bag called food vacuole. The food vacuole serves as a
temporary stomach secreting digestive juice, this step is known as digestion.
The digested food gets absorbed and diffuses into the cytoplasm and then
assimilated. Egestion of undigested food takes place at any point on the
surface of the body.
24. State two differences between arteries and
veins.
Answer. Arteries:
Arteries carry oxygenated blood, away from the heart except
pulmonary artery. These are thick-walled, highly muscular except arteries of
cranium and vertebral column.
Valves are absent. Blood in arteries moves with pressure.
Veins: Veins
carry deoxygenated blood, towards the heart except pulmonary veins. These are
thin-walled. Valves are present which provide unidirectional flow of
blood. Blood in veins moves under very
low pressure.
25. How are the alveoli designed to maximise
the exchange of gases?
Answer.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.
26. Explain the mechanism of gaseous exchange
between tissues and blood.
Answer. Exchange
of respiratory gases, i.e. oxygen and carbon dioxide occurs between the blood
and tissues.
In tissues, oxygen is used up for their activities
and carbon dioxide is released. The blood from lungs has high concentration of
oxygen and low concentration of carbon dioxide. Due to this, difference in
concentration of oxygen and carbon dioxide, the exchange of gases takes place
between tissue and blood.
27. Describe the mechanism of blood clotting.
Answer. Blood
Clotting: It is the mechanism that prevents the loss of blood at the site of an
injury or wound by forming a ‘blood clot’. The blood has platelet cells which
circulate around the body and plug these leaks by helping to clot the blood at
these points of injury to prevent it from excessive bleeding.
28. Why are white blood corpuscles called
‘soldiers’ of the body?
Answer. White
blood corpuscles can fight with the disease germs present in the body carried
by blood and help to maintain a healthy body. So, they are called as ‘soldiers’
of the body.
29. Which part of the human heart is considered
as pace-maker? Why is it so called?
Answer. Sino-atrial
node of the human heart is considered as pacemaker. Sino-atrial node is also
called as pacemaker because it determines the rate of heartbeat by determining
the rate of discharge of cardiac impulse.
30. Which enzyme initiates the digestion of
proteins ? Name the other enzyme produced by the same gland.
Answer. The
enzyme gastric pepsin initiates the digestion of proteins. The other enzyme
produced by the stomach is gastric lipase.
31. Name the first digestive organ that is
associated with the breakdown of proteins in humans. What are its three
releases?
Answer. The
first digestive organ in humans is the stomach. It releases proteolytic
enzymes, HCl and mucus.
32. Name two excretory products other than 02
and CO2 in plants.
Answer. The two
excretory products other than 02 and CO2 in plants are resins and
gums.
33. Why do the walls of the trachea not
collapse’when there is less air in it?
Answer.
Rings of cartilages are present in trachea. These rings support the trachea and
do not allow the trachea to collapse when there is less air in it.
34. What are enzymes? Name any one enzyme of
our digestive system and write its function. Answer. 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
35. (i) Write the balanced chemical equation
for the process of photosynthesis,
(ii) When do the
desert plants take up carbon dioxide and perform photosynthesis ?
Answer.
(i) Photosynthesis
can be represented using a chemical equation. The overall balanced equation is
(ii) Desert
plants open up their stomata during night and take in CO2. Stomata
remains close during the day time to prevent the loss of water by i
transpiration. They store the CO2 in their cells until the sun comes
out and they can carry on with photosynthesis during the day time.
36. Why there is no mixing of deoxygenated and
oxygenated blood in the human heart normally?
Answer. There
is no mixing of deoxygenated and oxygenated bloods in human heart due to the
presence of inter-ventricular septum. This septa completely divides the
ventricle into right and left to avoid mixing of blood.
37. Why are the walls of ventricles thicker
than the auricles ?
Answer. The
walls of ventricles are thicker than the auricles because ventricles have to
pump the blood to all the parts of the body during their contraction. To
counteract the backward pressure exerted by the blood, the walls of the
ventricles have to be thicker otherwise it may lead to bursting of heart.
38. Why do herbivores have longer, small
intestine than carnivores ?
Answer.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.
39. Write any two functions of large intestine
in man.
Answer. Functions
of large intestine in man are: (i) It serves to store the unabsorbed food
remnants temporarily. (ii) It concentrates the contents by absorbing water.
(iii) The movements of colon help to void the faeces through anus.
40. How would digestion of food be affected if
the bile duct is completely blocked? Explain. Answer. If the bile duct is
completely blocked, bile juice will not reach the small intestine and the
digestion of fats will be affected.
41. How would it affect the digestion of
proteins and carbohydrates in the duodenum of man if there is a blockage in the
pancreatic duct? Explain.
Answer. If
there is a blockage in the pancreatic duct, the pancreatic juice which contains
enzymes for the digestion of carbohydrates and proteins will not reach the
small intestine.
42. How is carbon dioxide obtained by (a)
aquatic plants and (b) terrestrial plants ?
Answer. (a)
Aquatic plants take up carbon dioxide dissolved in water. (b) Terrestrial
plants use carbon dioxide present in air.
43. Draw a neat labelled diagram of the
structure of a chloroplast. Answer.
44. Write correct sequence of four steps of
method for the preparation of temporary mount of a stained leaf peel.
Answer.
Take
a healthy leaf from the potted plant.
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.
Put
a few drops of safranin stain in a watch glass.
After
2-3 minutes take out the peel and place it on a clean glass slide.
Put
a drop of glycerin over the peel and place a clean covers lip gently over it
with the help of a needle.
Remove
the excess stain and glycerin with the help of blotting paper.
Observe
the slide under magnifications of the compound microscope.
SHORT ANSWER TYPE QUESTIONS[II]
[3 MARKS]
45. 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.
Answer. 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 greater amount of oxygen to sustain
life processes which cannot be fulfilled by the process of diffusion.
46. Draw a diagram of human excretory system
and label kidneys, ureters on it. Answer.
47. Name the acid presents in the following:
(i) Tomato (ii) Vinegar (iii) Tamarind
Answer.
(i) Oxalic
acid (ii) citric acid (iii) Tartaric acid.
48. State the role of the following in human
digestive system :
(i) Digestive enzymes (ii) Hydrochloric acid
(iii) Villi Answer.
(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 – Hydro chloric acid helps to kill the germs which might
have entered in to the system through food. It creates 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 help to
absorb digested food in to the blood stream.
49. 11.In mammals and birds why is it necessary
to separate oxygenated and de-oxygenated blood ?
Answer.
Mammals and birds are warm blooded animals. This means they can control their
body temperature and do not have to depend on environment for their body
temperature regulation. Because of this birds and mammals require optimum
oxidization of glucose which would be possible with good supply of oxygen. So
it is required to have separate oxygenated and deoxygenated blood to supply the
required amount of oxygen.
50. Draw a neat diagram of excretory system of
human beings and label on it:
(i) Left kidney (ii) Urinary bladder Answer.
Refer Q. No. 46
51. Draw a diagram of human respiratory system
and label on it : (i) Diaphragm (ii)
Larynx Answer.
52. List three characteristics of lungs which
make it an efficient respiratory surface. Answer. 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 in to the blood and carbon dioxide is given out in to 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.
53. (a) What is the role of HCl in our stomach
?
(b) What is emulsification of fats ?
(c) Which protein digesting enzyme is present
in pancreatic juice ?
Answer.
(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 gloubule fats into smaller fats droplets is known as emulsification.
(c) Trypsin
is the enzyme secreted by the pancreas which aids in digestion of proteins.
54. (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 human body.
Answer.
(a) Capillaries
(b)
55. List in tabular form three differences
between arteries and veins. Answer.
56. In human alimentary canal, name the site of
complete digestion of various components of food. Explain the process of
digestion.
Answer.In
small intestine, complete digestion of various components of food take place.
The process of digestion of food in mouth, stomach and small intestine in human
body are as follows:
Mouth:
Digestion of food begins in the mouth. Saliva present in 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
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. 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.
57. List the three kinds of blood vessels of
human circulatory system and write ¦ their functions in tabular form.
Answer.
Three types of blood vessels in human circulatory system are: Arteries, Veins
and Capillaries.
Their functions are tabulated below:
58. (a) “The breathing cycle is rhythmic
whereas exchange of gases is a continuous process”. Justify this statement.
(b) What happens if conducting tubes of
circulatory system develops a leak? State in brief, how could this be avoided?
(c) How opening and closing of stomata takes
place?
Answer.
(a) The breathing cycle involves inhalation and exhalation of air due to
alternate expansion and contraction of thoracic cavity. Thus it is a rhythmic
process. But 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 a 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.
59. Describe in brief the function of kidneys,
ureters, urinary bladder and urethra.
Answer. 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 bladder is like a holding tank for the urine
until it’s ready to be excreted. Urethra is the tube that connects the urinary
bladder to the outside of the body for excretion.
60. Explain the process of breakdown of glucose
in a cell (ii) in the absence of oxygen. Answer. 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 O2 is same. In this
step, glucose is broken down into pyruvate.
Second step which involves further breakdown of
private into simple compounds can take place in two different ways:
(a) In presence of O2: In the presence of
02, private is converted into C02 and water. Energy
released during aerobic respiration is much greater than that released during
an anaerobic respiration.
(b)In absence of O2: 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.
61. Draw a diagram of the front view of human
heart and label any six parts including at least two, that are concerned with
arterial blood supply to the heart muscles. Answer.
LONG ANSWER TYPE QUESTION [5
MARKS]
62. (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 ?
Answer.
(a) In
plants there are tiny pores called stomata on leaves and lenticels in stem
which facilitate the exchange of gases. Carbon dioxide is taken in and oxygen
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.
63. Draw a diagram of 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
Answer.
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.
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.
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.
Urinary bladder:
The urinary bladder is an expandable muscular sac that stores urine before it
is excreted out of the body through the urethra.
64. (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? Answer.(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.
65. (a) Draw a diagram of excretory system in
human beings and label the following parts.
Aorta, kidney,
urinary bladder and urethra.
(b) How is urine produced and eliminated ?
Answer.(a) Refer
Figure in Q. 63
(b) Blood from the heart comes into the kidneys
afferent and efferent arteriols from the renal arteries where it enters about
2-3 million nephrons per kidney. Then, it goes through the glomerulus a tugt or
bunch of blood capillaries and get rid of some of the unwanted substances like
urea, uric acid, creatinine in the blood and then continues through the renal
tubules. The loop of Henley, reabsorb certain substances such as water
(actually if body is dehydrated, body will send anti-diuretic hormone (ADH) to
kidneys to prevent extra water from going into urine and thus saving water for
body and get rid of anything else that isn’t wanted, then the urine goes
through ureters to bladder and then to urethra where it is excreted out of body
as urine.
66. (a) Draw a diagram of human respiratory
system and label the following:
(i) part where air is filtered by fine hair and
mucus
(ii) part which terminates in balloon – like
structures
(iii)
balloon
– like structures where exchange of gases takes place. (iv) part which
separates chest cavity from abdominal cavity.
(b) Why is the rate of breathing in aquatic
organisms much faster than in terrestrial organisms?
Answer.(a)
(b) Quantity of dissolved oxygen is fairly low in
water as compared to the amount of oxygen in air. Aquatic organisms therefore
have to breath faster than terrestrial organisms to absorb the required amount
of oxygen from the water.
67. Draw a neat diagram of excretory system of
human beings and label the following:
(i) Kidney
(ii) Ureter
(iii) Urinary Bladder
(iv) Urethra
Answer. Refer Figure in Q.
63
68. (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 body, Pulmonary veins from
lungs. (b) What is the advantage of
separate channels in mammals and birds for oxygenated and deoxygenated blood?
Answer.(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 large amount of oxygen. The separation of
oxygenated and deoxygenated blood provides high oxygen supply to the organs.
69. (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.
Answer.(a)
(b) Liver:
It synthesize and store bile juice secreted by gall bladder which breaks down
fats into fat globules. Pancreas: It secretes pancreatic juice which contains
protein-digesting and starch- digesting enzymes.
(c) The
organ which performs the following functions in humans are as follows:
(i) Absorption
of digested food – Small intestine. (ii)Absorption of water – Large intestine.
70. (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
Answer.(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 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 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.
71. (a) Draw a labelled diagram of the
respiratory system of human beings with diaphragm at the end of expiration.
(b) List four conditions required for efficient
gas exchange in an organism.
Answer.(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.
72. (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 human
digestive tract and mention their role.
(c) How is
required pH maintained in the stomach and small intestine? Answer.(a)
Pseudopodia serves the purpose of locomotion apart from
nutrition.
(b) The
salivary gland is associated with digestion of starch in 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 enzyme pepsin. Bile juice from liver
makes the food alkaline in small intestine for the pancreatic enzymes to act.
73. (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. Answer. (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.
|
Autotrophic
nutrition |
Heterotrophic
nutrition |
|
(i) In this, the organisms make their food from
carbon dioxide and water in the presence of sunlight and chlorophyll. |
(i) In
this, the organisms derive their food or nutrients from other living
organisms. |
|
(ii) All
green plants are autotrophic and use light as a source of energy for
synthesis. |
(ii) The energy is derived from the intake and
digestion of the organic substances. |
74. (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.” Answer.
(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 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. 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
decolorize 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 (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 the sunlight is essential for photosynthesis.
75. (a) What is meant by breathing? What
happens to the rate of breathing during vigorous exercise and why?
(b) Define translocation with respect to
transport in plants. Why is it essential for plants?
Where in plants are
the following synthesised?
(i) Sugar (iii)
Hormone
Answer.(a)
The process of taking in of oxygen from air in to 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 center 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 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.
76. (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?
Answer. (a) In
plants, there are tiny pores called stomata on leaves and lenticels in stem
which facilitate the exchange of gases. CO2 is taken in and O2 given out
(during photosynthesis) and vice-versa during respiration.
(b) Mechanism of Transport of Water and Minerals in a Plant
• The
vessels and tracheids of roots, stems and leaves in xylem tissue are
interconnected to form a continuous system of water-conducting channels
reaching all parts of the plant.
• The
cells of the roots in contact with the soil actively take up ions which creates
a difference in the ion concentration between the root and the soil.
• Thus,
there is steady movement of water into root xylem from the soil, creating a
column of water that is pushed upwards.
• Plant
uses another strategy to move water in the xylem upwards to the highest points
of the plant body.
• The
water which is lost through the stomata is replaced by water from the xylem
vessels in the leaf.
• Evaporation
of water molecules from the cells of a leaf creates a suction which pulls water
from the xylem cells of roots.
• This
loss of water is transpiration which helps in the absorption and upward
movement of water and minerals dissolved in it from roots to the leaves.
• Transpiration
becomes the major driving force in movement of water in the xylem during the
day when the stomata are open.
• This
mechanism is also known as cohesion of water theory or transpiration pull.
77. (a) Complete the glucose breakdown pathway
in case of aerobic respiration by filling the blanks.
(b) Name the molecule in the cell which stores
the energy produced at the end of the pathway.
(c) Why do we get cramps during vigorous
muscular activity?
Answer. (a) (1)
Pyruvate (3 carbon molecules) (2) Energy (3) Presence of oxygen (4) In
Mitochondria (5) Carbon dioxide (6) Water
(b) ATP
(c) Lactic
acid accumulation, in the absence of oxygen (anaerobic respiration)cause
cramps.
78. (a) Draw the structure of a nephron and
label the following on it: Glomerulus,
Bowman’s capsule, Renal artery, Collecting duct.
(b) What happens to glucose that enters the
nephron along with filtrate? Answer.(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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