Class 10 Science · Chapter 5

Life Processes

431 Class 10 Science questions on Life Processes from the NCERT textbook, NCERT Exemplar and CBSE board papers 2018–2026, each with its answer and a step-by-step solution.

NCERT exercises

Exercises (13) Intext Questions (Page 81) (4) Intext Questions (Page 87) (5) Intext Questions (Page 91) (4) Intext Questions (Page 96) (5) Intext Questions (Page 98) (3)

NCERT Exemplar exercises

Multiple Choice Questions (35) Short Answer Questions (37) Long Answer Questions (10)

CBSE Class 10 Science previous year papers, with answers →

Questions · page 19 of 22

Q361 CBSE 2023
Besides heart, the human circulatory system consists of a network of closed branching blood vessels and the blood that circulates continuously in all parts of the human body. The human heart is a muscular organ which is as big as our fist. It has four chambers — two upper chambers called atria and two lower chambers called ventricles. The right side of the human heart is separated from the left side by a dividing wall, which is known as septum.
1. (a)Name the smallest blood vessel and state its role in the circulation of blood.[1]
2. (b)Write the importance of platelets in the human blood.[1]
3. (c)(i)Write in tabular form, two differences between an artery and a vein.[2]
4. (c)(ii)OR : Why is blood circulation in the human heart called double circulation ? Explain.[2]
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Capillary; platelets clot blood; arteries carry blood away from the heart, veins towards it; double circulation takes blood through the heart twice.
(a) The smallest blood vessel is the **capillary**. Its wall is only one cell thick, and it is where the exchange of materials between the blood and the surrounding cells takes place — oxygen and digested food pass out to the cells and carbon dioxide and wastes pass into the blood; the capillaries then join up to form veins that carry the blood back. (b) Platelets circulate around the body and, when a vessel is cut or injured, help the blood to **clot** at that place, plugging the leak; this prevents loss of blood and stops the vessel system developing leaks. (c)(i) Artery: carries blood **away** from the heart, and has a thick, elastic, muscular wall with **no** valves, because the blood leaves the heart under high pressure. Vein: carries blood **towards** the heart, and has a thin wall with **valves** that prevent the blood flowing backwards, because the blood is no longer under pressure. (c)(ii) OR — It is called double circulation because in one complete circuit the blood passes through the heart **twice**. First, deoxygenated blood from the body enters the right atrium, goes to the right ventricle and is pumped to the lungs, returning oxygenated to the left atrium (pulmonary circulation); second, that blood goes from the left atrium to the left ventricle and is pumped to the whole body, returning deoxygenated to the right atrium (systemic circulation). The septum keeps the two sides separate so that oxygenated and deoxygenated blood do not mix, which allows an efficient supply of oxygen to the body.

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Q362 CBSE 2020
Which one of the following statements is correct about the human circulatory system ?
1. (a)Blood transports only oxygen and not carbon dioxide.
2. (b)Human heart has five chambers.
3. (c)Valves ensure that the blood does not flow backwards.
4. (d)Both oxygen-rich and oxygen-deficient blood gets mixed in the heart.
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(c) Valves ensure that the blood does not flow backwards.

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Q363 CBSE 2020
Anaerobic process
1. (a)takes place in yeast during fermentation.
2. (b)takes place in the presence of oxygen.
3. (c)produces only energy in the muscles of human beings.
4. (d)produces ethanol, oxygen and energy.
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(a) takes place in yeast during fermentation.

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Q364 CBSE 2020
In the excretory system of human beings, some substances in the initial filtrate such as glucose, amino acids, salts and water are selectively reabsorbed in
1. (a)Urethra
2. (b)Nephron
3. (c)Ureter
4. (d)Urinary bladder
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(b) Nephron

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Q365 CBSE 2020
Most of the digestion and absorption of the food takes place in the
1. (a)small intestine.
2. (b)liver.
3. (c)stomach.
4. (d)large intestine.
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(a) small intestine.

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Q366 CBSE 2020
Pseudopodia are
1. (a)small hair-like structures present on unicellular organisms.
2. (b)false feet developed in some unicellular organisms.
3. (c)long, tube-like structures coming out of the mouth.
4. (d)suckers which are attached to the walls of the intestines.
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(b) false feet developed in some unicellular organisms.

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Q367 CBSE 2020

Name the organ and site of photosynthesis in green plants. What are the raw materials essential for this process ? How are they obtained by a green plant ?

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Photosynthesis occurs in the leaf's chloroplasts, using carbon dioxide from air via stomata and water from soil via roots and xylem.
Organ: the green leaf (other green parts of the plant also photosynthesise). Site: the chloroplasts in the leaf cells, which contain chlorophyll. Raw materials: carbon dioxide and water. Carbon dioxide is obtained from the atmosphere; it enters the leaf through the stomata. Water is absorbed from the soil by the roots and carried to the leaves through the xylem.

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Q368 CBSE 2020

Name three kinds of blood vessels of the human circulatory system and write one function of each in a tabular form.

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Arteries carry blood away from the heart, veins bring blood back to the heart, and capillaries exchange materials between blood and cells.
Blood vessel: function Arteries: carry blood away from the heart to the various organs of the body. Veins: collect blood from the different organs and bring it back to the heart. Capillaries: allow the exchange of materials between the blood and the surrounding cells.

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Q369 CBSE 2020

Complete the following flow chart as per the given instructions :

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Mucus protects the stomach lining from acid, hydrochloric acid makes the acidic medium for pepsin and kills germs, and pepsin digests proteins.
a: Mucus; d: Protects the inner lining of the stomach from the action of the acid. b: Hydrochloric acid; e: Creates the acidic medium needed for the action of pepsin, and kills germs that enter with the food. c: Pepsin; f: Digests proteins. The three secretions may be written in any order, provided each function is placed under its own secretion.

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Q370 CBSE 2020
(a) State the role played by the following in the process of digestion.
1. (i)Enzyme trypsin
2. (ii)Enzyme lipase (b) List two functions of finger like projections present in the small intestine.
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Trypsin digests proteins and lipase breaks down emulsified fats; villi increase the surface area and absorb digested food.
(a) (i) Trypsin, an enzyme of the pancreatic juice, digests proteins in the small intestine, breaking them down into smaller peptides. (ii) Lipase, also in the pancreatic juice, breaks down emulsified fats into fatty acids and glycerol. (b) The finger-like projections (villi): (1) increase the surface area for absorption; (2) absorb the digested food, which their rich supply of blood vessels carries to every cell of the body.

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Q371 CBSE 2020
1. (a)In the process of respiration, state the function of alveoli.
2. (b)Rate of breathing in aquatic organisms is much faster than that in terrestrial organisms. Give reasons.
3. (c)Complete the following pathway showing the breakdown of glucose :
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Alveoli exchange gases; water holds little oxygen, so aquatic organisms breathe faster; the missing products are pyruvate and carbon dioxide.
(a) The alveoli are the sites of exchange of gases: oxygen from the inhaled air diffuses into the blood in the capillaries around them, and carbon dioxide from the blood passes into them to be breathed out. (b) The amount of oxygen dissolved in water is fairly low compared with the amount of oxygen in air, so aquatic organisms have to breathe much faster to obtain enough oxygen. (c) (i) Pyruvate (a 3-carbon molecule); (ii) Carbon dioxide.

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Q372 CBSE 2020

In the human body the site of absorption of digested food is the small intestine. How is the process of absorption carried out and why is absorption of digested food necessary ?

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Villi, with a large surface and rich blood supply, absorb digested food, which blood carries to all cells for energy, growth and repair.
Absorption: the inner lining of the small intestine has numerous finger-like projections called villi, which greatly increase the surface area for absorption. The villi have thin walls and are richly supplied with blood vessels. Digested food (glucose, amino acids, fatty acids and glycerol) passes through these walls into the blood, with fatty acids and glycerol going mainly into the lymph vessels (lacteals), and the blood carries it to each and every cell of the body. Why necessary: food is useful only when it reaches the cells, where it is used to obtain energy, to build new tissues and to repair old ones. Food that is not absorbed cannot be used and is passed out of the body.

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Q373 CBSE 2020

Describe the process of transpiration in plants. How does this process help the plant in remaining fresh and healthy ?

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Transpiration is loss of water vapour through stomata; the resulting pull draws water and minerals up, keeps cells turgid and cools the leaves.
Transpiration is the loss of water in the form of vapour from the aerial parts of a plant, mainly through the stomata of the leaves. Water brought to the leaf by the xylem evaporates from the leaf cells into the air spaces and diffuses out through the open stomata, whose opening is controlled by the guard cells. The water lost is replaced from the xylem, so a suction, the transpiration pull, draws a continuous column of water up from the roots. How it helps: (1) the transpiration pull keeps water rising from the roots, so the cells stay turgid and the plant remains fresh; (2) minerals dissolved in this water reach the leaves and other parts, and the leaves get water for photosynthesis, keeping the plant healthy; (3) evaporation cools the leaves and helps regulate their temperature.

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Q374 CBSE 2020

The plants were wilting in a garden and the gardener watered the plants. The plants became fresh again. Which part of the plant is responsible for conducting water in it and how does the process of conduction of water take place in plants ?

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Xylem conducts water: root pressure pushes it up and transpiration pull draws it up, so watered plants regain turgidity.
Part responsible: the xylem (its vessels and tracheids in roots, stems and leaves form one continuous water-conducting channel). Process: the root cells in contact with the soil actively take up ions, so water moves from the soil into the root and is pushed up the root xylem as a column (root pressure). Water evaporating from the leaf cells is lost as vapour through the stomata (transpiration); it is replaced from the xylem of the leaf, and the resulting suction, the transpiration pull, draws water up from the roots. Transpiration pull is the main force during the day, when the stomata are open, and root pressure matters more at night. When the garden was watered, the roots absorbed the water, the xylem carried it to the leaves and stems, and the cells became turgid again, so the plants became fresh.

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Q375 CBSE 2020
1. (a)Describe the structure and function of the basic filtering unit of kidney.
2. (b)List two factors on which reabsorption of water from urine depends ?
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The nephron filters blood in the glomerulus and reabsorbs useful substances in its tubule; water reabsorption depends on excess body water and dissolved waste.
(a) The basic filtering unit of the kidney is the nephron. Structure: each nephron has a cup-shaped Bowman’s capsule at its upper end, which holds a cluster of thin-walled blood capillaries called the glomerulus; blood enters the glomerulus through a branch of the renal artery and leaves through another arteriole. Bowman’s capsule leads into a long coiled tubule, surrounded by blood capillaries, which opens into a collecting duct. Function: blood is filtered in the glomerulus and the filtrate (water, glucose, amino acids, salts and urea) collects in Bowman’s capsule. As the filtrate passes along the tubule, useful substances such as glucose, amino acids, salts and a major amount of water are selectively reabsorbed into the surrounding capillaries. The remaining fluid, urine, passes into the collecting duct and on to the ureter. (b) The reabsorption of water depends on (i) the amount of excess water in the body and (ii) the amount of dissolved waste (such as urea) to be excreted.

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Q376 CBSE 2020
1. (a)Write the correct sequence of steps followed during journey of oxygen rich blood from lungs to various organs of human body.
2. (b)What happens when the system of blood vessels develop a leak ?
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Blood flows from the lungs through pulmonary veins, left atrium, left ventricle and aorta to the organs; platelets plug a leak by clotting.
(a) Oxygen-rich blood from the lungs $\to$ pulmonary veins $\to$ left atrium, which relaxes and collects the blood $\to$ the left atrium contracts $\to$ the blood passes into the left ventricle, which expands and collects it $\to$ the left ventricle contracts $\to$ the blood is pumped into the aorta $\to$ the aorta and its branches carry it to the various organs of the body. (b) A leak causes loss of blood and a fall in blood pressure, which reduces the efficiency of the pumping system. Platelets in the blood plug such leaks by helping the blood to clot at the point of injury.

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Q377 CBSE 2020
1. (a)How do leaves of plants help in excretion ? Explain briefly.
2. (b)Describe the structure and function of a nephron.
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Leaves excrete gases and water vapour through stomata and wastes in fallen leaves; a nephron filters blood and reabsorbs useful substances, leaving urine.
(a) Leaves help in excretion in these ways (any two): (1) oxygen produced in photosynthesis and carbon dioxide produced in respiration are given out through the stomata; (2) excess water is removed as water vapour by transpiration; (3) waste products stored in the vacuoles of leaf cells are removed when the old leaves fall off. (b) Structure: a nephron is the basic filtration unit of the kidney. It is a long, fine, coiled tubule whose one end forms a cup-shaped Bowman’s capsule around a cluster of thin-walled capillaries, the glomerulus (supplied by a branch of the renal artery); the tubule is surrounded by capillaries, and its other end opens into a collecting duct. Function: blood carrying nitrogenous wastes such as urea is filtered in the glomerulus, and the filtrate is collected in Bowman’s capsule. As the filtrate flows along the tubule, useful substances such as glucose, amino acids, salts and much of the water are selectively reabsorbed into the surrounding capillaries. The remaining fluid is urine, which passes into the collecting duct and then to the ureter.

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Q378 CBSE 2020
1. (a)Why is nutrition necessary for the human body ?
2. (b)What causes movement of food inside the alimentary canal ?
3. (c)Why is small intestine in herbivores longer than in carnivores ?
4. (d)What will happen if mucus is not secreted by the gastric glands ?
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Food gives energy, growth and repair; peristalsis moves it; herbivores need a longer small intestine for cellulose; without mucus, acid damages the stomach wall.
(a) Nutrition is necessary because food provides energy for the various metabolic processes of the body, and supplies materials for the formation of new cells (growth) and the repair of damaged or worn-out cells and tissues; it also helps the body develop resistance against diseases. (b) Peristalsis: the rhythmic contraction and relaxation of the muscles in the lining of the alimentary canal pushes the food forward. (c) Herbivores eat plant material rich in cellulose, which takes longer to digest, so they need a longer small intestine; carnivores eat meat, which is easier to digest, so their small intestine is shorter. (d) The inner lining of the stomach would not be protected from the hydrochloric acid, so the acid would damage (erode) the stomach wall, which can lead to ulcers.

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Q379 CBSE 2020
Give reasons :
1. (a)Ventricles have thicker muscular walls than atria.
2. (b)Transport system in plants is slow.
3. (c)Circulation of blood in aquatic vertebrates differs from that in terrestrial vertebrates.
4. (d)During the daytime, water and minerals travel faster through xylem as compared to the night.
5. (e)Veins have valves whereas arteries do not.
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Ventricles need more force; plants need little energy; fishes have single circulation; transpiration pull is stronger by day; veins carry low-pressure blood.
(a) The ventricles have to pump blood to the lungs and to various distant organs of the body, which needs far more force than the atria use to pass blood into the ventricles; so the ventricles have thicker muscular walls. (b) Plants do not move and many of their tissues are made of dead cells, so their energy requirement is low, and a slow transport system is enough. (c) In aquatic vertebrates (fishes) the blood goes through the heart only once during each cycle, heart $\to$ gills $\to$ body $\to$ heart (single circulation); in terrestrial vertebrates it goes through the heart twice during each cycle, heart $\to$ lungs $\to$ heart $\to$ body $\to$ heart (double circulation). (d) During the day the stomata are open and transpiration is high, so the transpiration pull is greater and water and minerals rise faster through the xylem than at night. (e) Veins carry blood back to the heart at low pressure, so they have valves to prevent the backflow of blood and keep it flowing in one direction; in arteries the high pressure from the heart keeps the blood moving forward, so no valves are needed.

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Q380 CBSE 2020
1. (a)Why is there a difference in the rate of breathing between aquatic organisms and terrestrial organisms? Explain.
2. (b)Draw a diagram of human respiratory system and label – pharynx, trachea, lungs, diaphragm and alveolar sac on it.
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Aquatic organisms breathe faster because water holds much less dissolved oxygen than air; the diagram shows the labelled air passage, lungs and diaphragm.
(a) Aquatic organisms take in the oxygen dissolved in water, while terrestrial organisms take in oxygen from the air. The amount of dissolved oxygen in water is much lower than the amount of oxygen in air, so aquatic organisms have to breathe much faster than terrestrial organisms to obtain enough oxygen. (b) The diagram of the human respiratory system shows the nasal passage leading to the pharynx and larynx and into the trachea, which divides into two bronchi, one to each lung; the bronchi branch into bronchioles, which end in alveolar sacs; the dome-shaped diaphragm lies below the lungs. The labels are pharynx, trachea, lungs, diaphragm and alveolar sac.

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