NCERT Solutions for Class 10 Science Chapter 5 Life Processes
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Page 1
NCERT
SOLUTIONS
CLASS - 10th
aglase .co
SOLUTIONS
CLASS - 10th
aglase .co
Page 2
Class : 10th
Subject : Science
Chapter : 6
Chapter Name : Life Processes
Q1 Why is diffusion insuf cient to meet the oxygen requirements of multicellular organisms like
humans?
Answer. Multicellular organisms such as humans possess complex body designs. They have
specialised cells and tissues for performing various necessary functions of the body such as intake
of food and oxygen. Unlike unicellular organisms, multicellular cells are not in direct contact with
the outside environment. Therefore, diffusion cannot meet their oxygen requirements.
Page : 95 , Block Name : Questions
Q2 What criteria do we use to decide whether something is alive?
Answer. Any visible movement such as walking, breathing, or growing is generally used to decide
whether something is alive or not. However, a living organism can also have movements, which
are not visible to the naked eye. Therefore, the presence of life processes is a fundamental
criterion that can be used to decide whether something is alive or not.
Page : 95 , Block Name : Questions
Q3 What are outside raw materials used for by an organism?
Answer. An organism uses outside raw materials mostly in the form of food and oxygen. The raw
materials required by an organism can be quite varied depending on the complexity of the
organism and its environment.
Page : 95 , Block Name : Questions
Q4 What processes would you consider essential for maintaining life?
Answer. Life processes such as nutrition, respiration, transportation, excretion, etc. are essential
for maintaining life.
Page : 95 , Block Name : Questions
Q1 What are the differences between autotrophic nutrition and heterotrophic nutrition?
Answer.
Subject : Science
Chapter : 6
Chapter Name : Life Processes
Q1 Why is diffusion insuf cient to meet the oxygen requirements of multicellular organisms like
humans?
Answer. Multicellular organisms such as humans possess complex body designs. They have
specialised cells and tissues for performing various necessary functions of the body such as intake
of food and oxygen. Unlike unicellular organisms, multicellular cells are not in direct contact with
the outside environment. Therefore, diffusion cannot meet their oxygen requirements.
Page : 95 , Block Name : Questions
Q2 What criteria do we use to decide whether something is alive?
Answer. Any visible movement such as walking, breathing, or growing is generally used to decide
whether something is alive or not. However, a living organism can also have movements, which
are not visible to the naked eye. Therefore, the presence of life processes is a fundamental
criterion that can be used to decide whether something is alive or not.
Page : 95 , Block Name : Questions
Q3 What are outside raw materials used for by an organism?
Answer. An organism uses outside raw materials mostly in the form of food and oxygen. The raw
materials required by an organism can be quite varied depending on the complexity of the
organism and its environment.
Page : 95 , Block Name : Questions
Q4 What processes would you consider essential for maintaining life?
Answer. Life processes such as nutrition, respiration, transportation, excretion, etc. are essential
for maintaining life.
Page : 95 , Block Name : Questions
Q1 What are the differences between autotrophic nutrition and heterotrophic nutrition?
Answer.
Page 3
Page : 101 , Block Name : Questions
Q2 Where do plants get each of the raw materials required for photosynthesis?
Answer. The following raw materials are required for photosynthesis:
i) The raw material CO enters from the atmosphere through stomata.
2
ii) Water is absorbed from the soil by the plant roots.
iii) Sunlight, an important component to manufacture food, is absorbed by the chlorophyll and
other green parts of the plants.
Page : 101 , Block Name : Questions
Q3 What is the role of the acid in our stomach?
Answer. The hydrochloric acid present in our stomach dissolves bits of food and creates an acidic
medium. In this acidic medium, enzyme pepsinogen is converted to pepsin, which is a protein-
digesting enzyme.
Page : 101 , Block Name : Questions
Q4 What is the function of digestive enzymes?
Answer. Digestive enzymes such as amylase, lipase, pepsin, trypsin, etc. help in the breaking down
complex food particles into simple ones. These simple particles can be easily absorbed by the
blood and thus transported to all the cells of the body.
Page : 101 , Block Name : Questions
Q5 How is the small intestine designed to absorb digested food?
Answer. The small intestine has millions of tiny nger-like projections called villi. These villi
increase the surface area for more ef cient food absorption. Within these villi, many blood vessels
Q2 Where do plants get each of the raw materials required for photosynthesis?
Answer. The following raw materials are required for photosynthesis:
i) The raw material CO enters from the atmosphere through stomata.
2
ii) Water is absorbed from the soil by the plant roots.
iii) Sunlight, an important component to manufacture food, is absorbed by the chlorophyll and
other green parts of the plants.
Page : 101 , Block Name : Questions
Q3 What is the role of the acid in our stomach?
Answer. The hydrochloric acid present in our stomach dissolves bits of food and creates an acidic
medium. In this acidic medium, enzyme pepsinogen is converted to pepsin, which is a protein-
digesting enzyme.
Page : 101 , Block Name : Questions
Q4 What is the function of digestive enzymes?
Answer. Digestive enzymes such as amylase, lipase, pepsin, trypsin, etc. help in the breaking down
complex food particles into simple ones. These simple particles can be easily absorbed by the
blood and thus transported to all the cells of the body.
Page : 101 , Block Name : Questions
Q5 How is the small intestine designed to absorb digested food?
Answer. The small intestine has millions of tiny nger-like projections called villi. These villi
increase the surface area for more ef cient food absorption. Within these villi, many blood vessels
Page 4
are present that absorb the digested food and carry it to the bloodstream. From the bloodstream,
the absorbed food is delivered to each and every cell of the body.
Page : 101 , Block Name : Questions
Q1 What advantage over an aquatic organism does a terrestrial organism have with regard to
obtaining oxygen for respiration?
Answer. Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals need
to utilize oxygen present in the water. Air contains more O as compared to water. Since the
2
content of O in air is high, the terrestrial animals do not have to breathe faster to get more
2
oxygen.
Therefore, unlike aquatic animals, terrestrial animals do not have to show various adaptations for
better gaseous exchange.
Page : 105 , Block Name : Questions
Q2 What are the different ways in which glucose is oxidised to provide energy in various
organisms?
Answer. Glucose is rst broken down in the cell cytoplasm into a three carbon molecule called
pyruvate. Pyruvate is further broken down by different ways to provide energy.
The breakdown of glucose by different pathways can be illustrated as follows.
In yeast and human muscle cells, the breakdown of pyruvate occurs in the absence of
the absorbed food is delivered to each and every cell of the body.
Page : 101 , Block Name : Questions
Q1 What advantage over an aquatic organism does a terrestrial organism have with regard to
obtaining oxygen for respiration?
Answer. Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals need
to utilize oxygen present in the water. Air contains more O as compared to water. Since the
2
content of O in air is high, the terrestrial animals do not have to breathe faster to get more
2
oxygen.
Therefore, unlike aquatic animals, terrestrial animals do not have to show various adaptations for
better gaseous exchange.
Page : 105 , Block Name : Questions
Q2 What are the different ways in which glucose is oxidised to provide energy in various
organisms?
Answer. Glucose is rst broken down in the cell cytoplasm into a three carbon molecule called
pyruvate. Pyruvate is further broken down by different ways to provide energy.
The breakdown of glucose by different pathways can be illustrated as follows.
In yeast and human muscle cells, the breakdown of pyruvate occurs in the absence of
Page 5
oxygen whereas in mitochondria, the breakdown of pyruvate occurs in the presence of oxygen.
Page : 105 , Block Name : Questions
Q3 How is oxygen and carbon dioxide transported in human beings?
Answer. Haemoglobin transports oxygen molecule to all the body cells for cellular respiration. The
haemoglobin pigment present in the blood gets attached to four O molecules that are obtained
2
from breathing. It thus forms oxyhaemoglobin and the blood becomes oxygenated. This
oxygenated blood is then distributed to all the body cells by the heart. After giving away O to the
2
body cells, blood takes away CO which is the end product of cellular respiration. Now the blood
2
becomes de-oxygenated. Since haemoglobin pigment has less af nity for CO , CO is mainly
2 2
transported in the
dissolved form. This de-oxygenated blood gives CO to lung alveoli and takes O in return.
2 2
Page : 105 , Block Name : Questions
Q4 How are the lungs designed in human beings to maximise the area for exchange of gases?
Answer. The exchange of gases takes place between the blood of the capillaries that surround the
alveoli and the gases present in the alveoli. Thus, alveoli are the site for exchange of gases. The
lungs get lled up with air during the process of inhalation as ribs are lifted up and diaphragm is
attened. The air that is rushed inside the lungs lls the numerous alveoli present in the lungs.
lung contains 300-350 million alveoli. These numerous alveoli increase the surface area for
gaseous exchange making the process of respiration more ef cient.
Page : 105 , Block Name : Questions
Q1 What are the components of the transport system in human beings? What are the functions of
these components?
Answer. The main components of the transport system in human beings are the heart, blood, and
blood vessels.
Page : 105 , Block Name : Questions
Q3 How is oxygen and carbon dioxide transported in human beings?
Answer. Haemoglobin transports oxygen molecule to all the body cells for cellular respiration. The
haemoglobin pigment present in the blood gets attached to four O molecules that are obtained
2
from breathing. It thus forms oxyhaemoglobin and the blood becomes oxygenated. This
oxygenated blood is then distributed to all the body cells by the heart. After giving away O to the
2
body cells, blood takes away CO which is the end product of cellular respiration. Now the blood
2
becomes de-oxygenated. Since haemoglobin pigment has less af nity for CO , CO is mainly
2 2
transported in the
dissolved form. This de-oxygenated blood gives CO to lung alveoli and takes O in return.
2 2
Page : 105 , Block Name : Questions
Q4 How are the lungs designed in human beings to maximise the area for exchange of gases?
Answer. The exchange of gases takes place between the blood of the capillaries that surround the
alveoli and the gases present in the alveoli. Thus, alveoli are the site for exchange of gases. The
lungs get lled up with air during the process of inhalation as ribs are lifted up and diaphragm is
attened. The air that is rushed inside the lungs lls the numerous alveoli present in the lungs.
lung contains 300-350 million alveoli. These numerous alveoli increase the surface area for
gaseous exchange making the process of respiration more ef cient.
Page : 105 , Block Name : Questions
Q1 What are the components of the transport system in human beings? What are the functions of
these components?
Answer. The main components of the transport system in human beings are the heart, blood, and
blood vessels.
Page 6
i) Heart pumps oxygenated blood throughout the body. It receives deoxygenated blood from the
various body parts and sends this impure blood to the lungs for oxygenation.
ii) Being a uid connective tissue, blood helps in the transport of oxygen, nutrients, CO , and
2
nitrogenous wastes.
iii) The blood vessels (arteries, veins, and capillaries) carry blood either away from the heart to
various organs or from various organs back to the heart.
Page : 110 , Block Name : Questions
Q2 Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Answer. Warm-blooded animals such as birds and mammals maintain a constant body
temperature by cooling themselves when they are in a hotter environment and by warming their
bodies when they are in a cooler environment. Hence, these animals require more oxygen (O ) for2
more cellular respiration so that they can produce more energy to maintain their body
temperature. Thus, it is necessary for them to separate oxygenated and de-oxygenated blood, so
that their circulatory system is more ef cient and can maintain their constant body temperature.
Page : 110 , Block Name : Questions
Q3 What are the components of the transport system in highly organised plants?
Answer. In highly organised plants, there are two different types of conducting tissues — xylem
and phloem. Xylem conducts water and minerals obtained from the soil (via roots) to the rest of
the plant. Phloem transports food materials from the leaves to different parts of the plant body.
Page : 110 , Block Name : Questions
Q4 How are water and minerals transported in plants?
Answer. The components of xylem tissue (tracheids and vessels) of roots, stems, and leaves are
interconnected to form a continuous system of water-conducting channels that reaches all parts of
the plant. Transpiration creates a suction pressure, as a result of which water is forced into the
xylem cells of the roots. Then there is a steady movement of water from the root xylem to all the
plant parts through the interconnected water-conducting channels.
various body parts and sends this impure blood to the lungs for oxygenation.
ii) Being a uid connective tissue, blood helps in the transport of oxygen, nutrients, CO , and
2
nitrogenous wastes.
iii) The blood vessels (arteries, veins, and capillaries) carry blood either away from the heart to
various organs or from various organs back to the heart.
Page : 110 , Block Name : Questions
Q2 Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Answer. Warm-blooded animals such as birds and mammals maintain a constant body
temperature by cooling themselves when they are in a hotter environment and by warming their
bodies when they are in a cooler environment. Hence, these animals require more oxygen (O ) for2
more cellular respiration so that they can produce more energy to maintain their body
temperature. Thus, it is necessary for them to separate oxygenated and de-oxygenated blood, so
that their circulatory system is more ef cient and can maintain their constant body temperature.
Page : 110 , Block Name : Questions
Q3 What are the components of the transport system in highly organised plants?
Answer. In highly organised plants, there are two different types of conducting tissues — xylem
and phloem. Xylem conducts water and minerals obtained from the soil (via roots) to the rest of
the plant. Phloem transports food materials from the leaves to different parts of the plant body.
Page : 110 , Block Name : Questions
Q4 How are water and minerals transported in plants?
Answer. The components of xylem tissue (tracheids and vessels) of roots, stems, and leaves are
interconnected to form a continuous system of water-conducting channels that reaches all parts of
the plant. Transpiration creates a suction pressure, as a result of which water is forced into the
xylem cells of the roots. Then there is a steady movement of water from the root xylem to all the
plant parts through the interconnected water-conducting channels.
Page 7
Page : 110 , Block Name : Questions
Q5 How is food transported in plants?
Answer. Phloem transports food materials from the leaves to different parts of the plant body. The
transportation of food in phloem is achieved by utilizing energy from ATP As a result of this, the
osmotic pressure in the tissue increases causing water to move into it. This pressure moves the
material in the phloem to the tissues which have less pressure. This is helpful in moving materials
according to the needs of the plant. For example, the food material, such as sucrose, is transported
into the phloem tissue using ATP energy.
Page : 110 , Block Name : Questions
Q1 Describe the structure and functioning of nephrons.
Answer. Nephrons are the basic ltering units of kidneys. Each kidney possesses large number of
nephrons, approximately 1-1.5 million. The main components of the nephron are glomerulus,
Bowman's capsule, and a long renal tubule.
Q5 How is food transported in plants?
Answer. Phloem transports food materials from the leaves to different parts of the plant body. The
transportation of food in phloem is achieved by utilizing energy from ATP As a result of this, the
osmotic pressure in the tissue increases causing water to move into it. This pressure moves the
material in the phloem to the tissues which have less pressure. This is helpful in moving materials
according to the needs of the plant. For example, the food material, such as sucrose, is transported
into the phloem tissue using ATP energy.
Page : 110 , Block Name : Questions
Q1 Describe the structure and functioning of nephrons.
Answer. Nephrons are the basic ltering units of kidneys. Each kidney possesses large number of
nephrons, approximately 1-1.5 million. The main components of the nephron are glomerulus,
Bowman's capsule, and a long renal tubule.
Page 8
Functioning of a nephron:
i) The blood enters the kidney through the renal artery, which branches into many
capillaries associated with glomerulus.
ii) The water and solute are transferred to the nephron at Bowman's capsule.
iii) In the proximal tubule, some substances such as amino acids, glucose, and salts
are selectively reabsorbed and unwanted molecules are added in the urine.
iv) The ltrate then moves down into the loop of Henle, where more water is absorbed.
v) From here, the ltrate moves upwards into the distal tubule and nally to the collecting duct.
Collecting duct collects urine from many nephrons.
vi) The urine formed in each kidney enters a long tube called ureter. From ureter, it gets
transported to the urinary bladder an
Page : 112 , Block Name : Questions
Q2 What are the methods used by plants to get rid of excretory products?
Answer. Plants can get rid of excess of water by transpiration. Waste materials may be stored in
the cell vacuoles or as gum and resin, especially in old xylem. It is also stored in the leaves that
later fall off.
Page : 112 , Block Name : Questions
Q3 How is the amount of urine produced regulated?
Answer. The amount of urine produced depends on the amount of excess water and dissolved
wastes present in the body. Some other factors such as habitat of an organism and hormone such
as Antidiuretic hormone (ADH) also regulates the amount of urine produced.
Page : 112 , Block Name : Questions
Q1 The kidneys in human beings are a part of the system for
(a) nutrition.
(b) respiration.
i) The blood enters the kidney through the renal artery, which branches into many
capillaries associated with glomerulus.
ii) The water and solute are transferred to the nephron at Bowman's capsule.
iii) In the proximal tubule, some substances such as amino acids, glucose, and salts
are selectively reabsorbed and unwanted molecules are added in the urine.
iv) The ltrate then moves down into the loop of Henle, where more water is absorbed.
v) From here, the ltrate moves upwards into the distal tubule and nally to the collecting duct.
Collecting duct collects urine from many nephrons.
vi) The urine formed in each kidney enters a long tube called ureter. From ureter, it gets
transported to the urinary bladder an
Page : 112 , Block Name : Questions
Q2 What are the methods used by plants to get rid of excretory products?
Answer. Plants can get rid of excess of water by transpiration. Waste materials may be stored in
the cell vacuoles or as gum and resin, especially in old xylem. It is also stored in the leaves that
later fall off.
Page : 112 , Block Name : Questions
Q3 How is the amount of urine produced regulated?
Answer. The amount of urine produced depends on the amount of excess water and dissolved
wastes present in the body. Some other factors such as habitat of an organism and hormone such
as Antidiuretic hormone (ADH) also regulates the amount of urine produced.
Page : 112 , Block Name : Questions
Q1 The kidneys in human beings are a part of the system for
(a) nutrition.
(b) respiration.
Page 9
(c) excretion.
(d) transportation.
Answer. (c) In human beings, the kidneys are a part of the system for excretion.
Page : 113 , Block Name : Exercise
Q2 The xylem in plants are responsible for
(a) transport of water.
(b) transport of food.
(c) transport of amino acids.
(d) transport of oxygen.
Answer. (a) In a plant, the xylem is responsible for transport of water.
Page : 113 , Block Name : Exercise
Q3 The autotrophic mode of nutrition requires
(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.
Answer. (d) The autotrophic mode of nutrition requires carbon dioxide, water, chlorophyll and
sunlight.
Page : 113 , Block Name : Exercise
Q4 The breakdown of pyruvate to give carbon dioxide, water and energy takes place in (a)
cytoplasm.
(b) mitochondria.
(c) chloroplast.
(d) nucleus.
Answer. (b) The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
mitochondria.
Page : 113 , Block Name : Exercise
Q5 How are fats digested in our bodies? Where does this process take place?
Answer. Fats are present in the form of large globules in the small intestine. The small intestine
gets the secretions in the form of bile juice and pancreatic juice respectively from the liver and the
pancreas. The bile salts (from the liver) break down the large fat globules into smaller globules so
that the pancreatic enzymes can easily act on them. This is referred to as emulsi cation of fats. It
takes place in the small intestine.
(d) transportation.
Answer. (c) In human beings, the kidneys are a part of the system for excretion.
Page : 113 , Block Name : Exercise
Q2 The xylem in plants are responsible for
(a) transport of water.
(b) transport of food.
(c) transport of amino acids.
(d) transport of oxygen.
Answer. (a) In a plant, the xylem is responsible for transport of water.
Page : 113 , Block Name : Exercise
Q3 The autotrophic mode of nutrition requires
(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.
Answer. (d) The autotrophic mode of nutrition requires carbon dioxide, water, chlorophyll and
sunlight.
Page : 113 , Block Name : Exercise
Q4 The breakdown of pyruvate to give carbon dioxide, water and energy takes place in (a)
cytoplasm.
(b) mitochondria.
(c) chloroplast.
(d) nucleus.
Answer. (b) The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
mitochondria.
Page : 113 , Block Name : Exercise
Q5 How are fats digested in our bodies? Where does this process take place?
Answer. Fats are present in the form of large globules in the small intestine. The small intestine
gets the secretions in the form of bile juice and pancreatic juice respectively from the liver and the
pancreas. The bile salts (from the liver) break down the large fat globules into smaller globules so
that the pancreatic enzymes can easily act on them. This is referred to as emulsi cation of fats. It
takes place in the small intestine.
Page 10
Page : 113 , Block Name : Exercise
Q6 What is the role of saliva in the digestion of food?
Answer. Saliva is secreted by the salivary glands, located under the tongue. It moistens the food
for easy swallowing. It contains a digestive enzyme called salivary amylase, which breaks down
starch into sugar.
Page : 113 , Block Name : Exercise
Q7 What are the necessary conditions for autotrophic nutrition and what are its byproducts?
Answer. Autotrophic nutrition takes place through the process of photosynthesis. Carbon dioxide,
water, chlorophyll pigment, and sunlight are the necessary conditions required for autotrophic
nutrition. Carbohydrates (food) and 02 are the by-products of photosynthesis.
Sunlight
6CO2 + 6H2 O C6 H12 O6 + 6O2
Chlorophyll
Page : 113 , Block Name : Exercise
Q8 What are the differences between aerobic and anaerobic respiration? Name some organisms
that use the anaerobic mode of respiration.
Answer.
Anaerobic respiration occurs in the roots of some waterlogged plants, some parasitic
worms, animal muscles, and some micro-organisms such as yeasts.
Page : 113 , Block Name : Exercise
Q9 How are the alveoli designed to maximise the exchange of gases?
Answer. The alveoli are the small balloon-like structures present in the lungs. The walls of the
alveoli consist of extensive net-vvork of blood vessels. Each lung contains 300-350 million alveoli,
Q6 What is the role of saliva in the digestion of food?
Answer. Saliva is secreted by the salivary glands, located under the tongue. It moistens the food
for easy swallowing. It contains a digestive enzyme called salivary amylase, which breaks down
starch into sugar.
Page : 113 , Block Name : Exercise
Q7 What are the necessary conditions for autotrophic nutrition and what are its byproducts?
Answer. Autotrophic nutrition takes place through the process of photosynthesis. Carbon dioxide,
water, chlorophyll pigment, and sunlight are the necessary conditions required for autotrophic
nutrition. Carbohydrates (food) and 02 are the by-products of photosynthesis.
Sunlight
6CO2 + 6H2 O C6 H12 O6 + 6O2
Chlorophyll
Page : 113 , Block Name : Exercise
Q8 What are the differences between aerobic and anaerobic respiration? Name some organisms
that use the anaerobic mode of respiration.
Answer.
Anaerobic respiration occurs in the roots of some waterlogged plants, some parasitic
worms, animal muscles, and some micro-organisms such as yeasts.
Page : 113 , Block Name : Exercise
Q9 How are the alveoli designed to maximise the exchange of gases?
Answer. The alveoli are the small balloon-like structures present in the lungs. The walls of the
alveoli consist of extensive net-vvork of blood vessels. Each lung contains 300-350 million alveoli,
Page 11
making it a total of approximately 700 million in both the lungs. The alveolar surface when spread
out covers about 80 m2 area. This large surface area makes the gaseous exchange more ef cient.
Page : 113 , Block Name : Exercise
Q10 What would be the consequences of a de ciency of hemoglobin in our bodies?
Answer. Hemoglobin is the respiratory pigment that transports oxygen to the body cells for
cellular respiration. Therefore, de ciency of haemoglobin in blood can affect the oxygen supplying
capacity of blood. This can lead to de ciency of oxygen in the body cells. It can also lead to a
disease called anaemia.
Page : 113 , Block Name : Exercise
Q11 Describe double circulation of blood in human beings. Why is it necessary?
Answer. The human heart is divided into four chambers — the right atrium, the right ventricle, the
left atrium, and the left ventricle. Flow of blood in the heart:
— The heart has superior and inferior vena cava, which carries de-oxygenated blood from the
upper and lower regions of the body respectively and supplies this de-oxygenated blood to the
right atrium of the heart.
out covers about 80 m2 area. This large surface area makes the gaseous exchange more ef cient.
Page : 113 , Block Name : Exercise
Q10 What would be the consequences of a de ciency of hemoglobin in our bodies?
Answer. Hemoglobin is the respiratory pigment that transports oxygen to the body cells for
cellular respiration. Therefore, de ciency of haemoglobin in blood can affect the oxygen supplying
capacity of blood. This can lead to de ciency of oxygen in the body cells. It can also lead to a
disease called anaemia.
Page : 113 , Block Name : Exercise
Q11 Describe double circulation of blood in human beings. Why is it necessary?
Answer. The human heart is divided into four chambers — the right atrium, the right ventricle, the
left atrium, and the left ventricle. Flow of blood in the heart:
— The heart has superior and inferior vena cava, which carries de-oxygenated blood from the
upper and lower regions of the body respectively and supplies this de-oxygenated blood to the
right atrium of the heart.
Page 12
Flow of blood in the human heart
i) The right atrium then contracts and passes the de-oxygenated blood to the right
ventricle, through an auriculo-ventricular aperture.
ii) Then the right ventricle contracts and passes the de-oxygenated blood into the two pulmonary
arteries, which pumps it to the lungs where the blood becomes oxygenated.
iii) From the lungs, the pulmonary veins transport the oxygenated blood to the left atrium of the
heart.
iv) Then the left atrium contracts and through the auriculo-ventricular aperture, the oxygenated
blood enters the left ventricle.
v) The blood passes to aorta from the left ventricle. The aorta gives rise to many arteries
that distribute the oxygenated blood to all the regions of the body.
Schematic diagram of blood circulation in humans. Therefore, the blood goes twice through the
heart. This is known as double circulation.
Importance of double circulation:
The separation of oxygenated and de-oxygenated blood allows a more ef cient supply of oxygen to
the body cells. This ef cient system of oxygen supply is very useful in warm-blooded animals such
as human beings.
As we know, warm-blooded animals have to maintain a constant body temperature by
cooling themselves when they are in a hotter environment and by warming their bodies when they
are in a cooler environment. Hence, they require more 02 for more respiration so that they can
i) The right atrium then contracts and passes the de-oxygenated blood to the right
ventricle, through an auriculo-ventricular aperture.
ii) Then the right ventricle contracts and passes the de-oxygenated blood into the two pulmonary
arteries, which pumps it to the lungs where the blood becomes oxygenated.
iii) From the lungs, the pulmonary veins transport the oxygenated blood to the left atrium of the
heart.
iv) Then the left atrium contracts and through the auriculo-ventricular aperture, the oxygenated
blood enters the left ventricle.
v) The blood passes to aorta from the left ventricle. The aorta gives rise to many arteries
that distribute the oxygenated blood to all the regions of the body.
Schematic diagram of blood circulation in humans. Therefore, the blood goes twice through the
heart. This is known as double circulation.
Importance of double circulation:
The separation of oxygenated and de-oxygenated blood allows a more ef cient supply of oxygen to
the body cells. This ef cient system of oxygen supply is very useful in warm-blooded animals such
as human beings.
As we know, warm-blooded animals have to maintain a constant body temperature by
cooling themselves when they are in a hotter environment and by warming their bodies when they
are in a cooler environment. Hence, they require more 02 for more respiration so that they can
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produce more energy to maintain their body temperature. Thus, the circulatory system of humans
is more ef cient because of the double circulatory heart.
Page : 113 , Block Name : Exercise
Q12 What are the differences between the transport of materials in xylem and phloem?
Answer.
Page : 113 , Block Name : Exercise
Q13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to
their structure and functioning.
Answer.
Page : 113 , Block Name : Exercise
is more ef cient because of the double circulatory heart.
Page : 113 , Block Name : Exercise
Q12 What are the differences between the transport of materials in xylem and phloem?
Answer.
Page : 113 , Block Name : Exercise
Q13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to
their structure and functioning.
Answer.
Page : 113 , Block Name : Exercise
Document Details
| Board / Org | NCERT |
| Exam | Class 10 |
| Type | Solution |
| Pages | 13 |
| Language | english |
| Updated | 22 Jul 2026 |