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.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 21 of 22

1. Q401 CBSE 2019
   What ​is ​photosynthesis ? ​Explain its ​mechanism.
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   Photosynthesis is the making of carbohydrates from carbon dioxide and water by green plants using sunlight and chlorophyll, with oxygen released.

   Photosynthesis is the process by which green plants make carbohydrates (food) from carbon dioxide and water in the presence of sunlight and chlorophyll, giving out oxygen: $6{\text{CO}}_2+12{\text{H}}_2\text{O}\underset{\text{sunlight}}{\overset{\text{chlorophyll}}{\to }}{\text{C}}_6{\text{H}}_{12}{\text{O}}_6+6{\text{O}}_2+6{\text{H}}_2\text{O}$ Mechanism: (i) Chlorophyll absorbs light energy. (ii) The light energy is converted into chemical energy. (iii) Water molecules are split into hydrogen and oxygen, and the oxygen is released. (iv) Carbon dioxide is reduced to carbohydrate, using the hydrogen and the chemical energy.

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2. Q402 CBSE 2019
   List in ​tabular ​form three ​differences between ​blood and lymph.
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   Blood is red and flows in arteries, veins and capillaries; lymph is colourless, flows in lymph vessels and carries absorbed fat.

   Differences between blood and lymph (any three): (1) Colour: Blood is red, because its red blood cells contain haemoglobin. Lymph is colourless, because it has no red blood cells. (2) Where it flows: Blood flows in arteries, veins and capillaries. Lymph flows in lymph vessels (lymphatic vessels). (3) What it carries: Blood carries oxygen, digested and absorbed food, carbon dioxide and nitrogenous wastes. Lymph carries digested and absorbed fat from the intestine and drains excess fluid from the tissues back into the blood. (4) Composition: Blood has plasma, red blood cells, white blood cells and platelets. Lymph is like plasma with less protein, and contains white blood cells but no red blood cells.

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3. Q403 CBSE 2019
   What ​is ​transpiration ​? ​List its two functions.
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   Transpiration is loss of water vapour from aerial parts, mainly through stomata; it pulls water and minerals upwards and cools the plant.

   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. Two functions: (i) It creates a suction (transpiration pull) that helps in the absorption and upward movement of water, and of the minerals dissolved in it, from the roots to the leaves. (ii) It helps in temperature regulation: the evaporation of water from the leaves cools the plant.

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4. Q404 CBSE 2019
   1. (a)What is translocation ​? Why is it ​essential for ​plants ?
   2. (b)Where do ​the substances in ​plants reach as ​a result ​of ​translocation ?
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   Translocation moves food from the leaves through the phloem to all parts, reaching storage organs of roots, fruits and seeds, and growing parts.

   (a) Translocation is the transport of the soluble products of photosynthesis (food) from the leaves to the other parts of the plant, through the phloem. It is essential because only the green parts (mainly the leaves) make food, while every part of the plant needs food for energy and growth; translocation provides food to all parts of the plant and carries the surplus to storage organs. (b) The substances reach the storage organs of roots, fruits and seeds, and the growing parts (organs) of the plant.

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5. Q405 CBSE 2019
   What ​is ​haemoglobin ​? ​State the consequences ​of ​deficiency of haemoglobin in ​our bodies.
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   Haemoglobin is the oxygen-carrying pigment of red blood cells; its deficiency lowers oxygen supply to tissues and causes anaemia.

   Haemoglobin is the respiratory pigment present in the red blood cells (an iron-containing protein). It has a very high affinity for oxygen and transports oxygen from the lungs to the tissues. Consequences of its deficiency: (i) the oxygen-carrying capacity of the blood falls, so less oxygen is supplied to the body tissues and the cells get less energy from respiration; (ii) the person suffers from anaemia, with tiredness, weakness, breathlessness and a pale look.

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6. Q406 CBSE 2019
   (a) Write ​the function of the following in the ​human ​alimentary ​canal :

   1. (i)Saliva
   2. (ii)$\text{HCl}$ ​in ​stomach
   3. (iii)Bile juice
   4. (iv)Villi (b) Write one function each ​of the following enzymes : (i) Pepsin (ii) Lipase
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   Saliva digests starch, HCl aids pepsin and kills germs, bile emulsifies fats, villi absorb food; pepsin digests proteins and lipase digests fats.

   (a)(i) Saliva: its enzyme salivary amylase breaks down starch into sugar (maltose); saliva also wets the food so that it can be swallowed easily. (a)(ii) $\text{HCl}$ in the stomach: it makes the medium acidic, which helps the enzyme pepsin act, and it kills germs that enter with the food. (a)(iii) Bile juice: it emulsifies fats, breaking large fat globules into smaller ones so that lipase can act on them, and it makes the acidic food from the stomach alkaline for the pancreatic enzymes. (a)(iv) Villi: they increase the surface area for the absorption of digested food; their blood vessels carry the absorbed food to all the cells of the body. (b)(i) Pepsin: it digests proteins (into smaller peptides) in the stomach. (b)(ii) Lipase: it digests fats, breaking emulsified fats into fatty acids and glycerol.

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7. Q407 CBSE 2019
   1. (a)​Write two water ​conducting tissues present ​in plants. How does water ​enter continuously into the ​root ​xylem ?
   2. (b)Explain why plants ​have low energy needs as compared to ​animals.
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   Xylem vessels and tracheids conduct water; ion uptake draws water into the root xylem; plants need little energy as they do not move.

   (a) The two water-conducting tissues are xylem vessels and xylem tracheids. Water enters the root xylem continuously because the root cells in contact with the soil actively take up ions. This creates a difference in the concentration of ions between the root and the soil, so water moves from the soil into the root to remove the difference. As the uptake of ions goes on, there is a steady movement of water into the root xylem, which pushes the column of water upwards. (b) Plants do not move, and plant bodies have a large proportion of dead cells in many tissues, which need no energy. So plants have low energy needs compared with animals, and a relatively slow transport system is enough for them.

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8. Q408 CBSE 2019
   1. (a)Define ​the term excretion. ​Why should ​animals ​excrete waste matter ?
   2. (b)Name the main excretory organ of human beings and state the form in which the excretory matter is thrown ​out of the body.
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   Excretion is removal of harmful metabolic wastes, which are toxic if retained; the kidneys are the main excretory organs and wastes leave as urine.

   (a) Excretion is the biological process by which the harmful metabolic wastes, mainly nitrogenous wastes such as urea, are removed from the body. Animals must excrete these wastes because they are toxic: if they accumulated, they would poison the cells and upset the composition of the body fluids, harming the animal. (b) The main excretory organs of human beings are the kidneys (a pair). The excretory matter is thrown out of the body as urine, that is, urea and other wastes dissolved in water.

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9. Q409 CBSE 2019
   Draw a diagram of human excretory system ​and label the following ​:

   1. (i)​Urinary bladder
   2. (ii)​Left ​kidney
   3. (iii)​Left ​ureter
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   Diagram of the human excretory system in front view, with the urinary bladder, left kidney and left ureter labelled.

   The diagram (see the solution figure) shows the human excretory system as seen from the front: two bean-shaped kidneys high in the abdomen on either side of the backbone, a ureter from each kidney down to the urinary bladder, and the urethra leading out of the bladder; the aorta and the vena cava run down between the kidneys, joined to them by the renal arteries and veins. Labels: (i) Urinary bladder: the muscular bag low in the middle of the abdomen into which both ureters open. (ii) Left kidney: the kidney on the person's left side, which is on the right-hand side of a diagram drawn as seen from the front. (iii) Left ureter: the tube that carries urine from the left kidney down to the urinary bladder.

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10. Q410 CBSE 2019
    List ​six ​methods used by ​plants ​to ​get rid ​of their excretory products.
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    Plants get rid of wastes through stomata, transpiration, vacuoles, falling leaves, resins and gums, and release into the soil.

    (i) Gaseous wastes, oxygen from photosynthesis and carbon dioxide from respiration, diffuse out through the stomata of leaves. (ii) Excess water is removed by transpiration. (iii) Many waste products are stored in the vacuoles of cells. (iv) Some waste products are stored in leaves, which later fall off. (v) Some waste products are stored as resins and gums, especially in old xylem. (vi) Some waste substances are excreted into the soil around the roots. Storing wastes in the bark, which peels off, is another correct method.

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11. Q411 CBSE 2019
    A student has ​set up an ​apparatus to ​show that “${\text{CO}}_2$ is released ​during respiration”. After about 1 ​hour he observes ​no change in the water level in the delivery tube. Write two possible ​reasons ​for the failure of the experiment.
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    Two reasons: the apparatus was not air-tight, or the KOH solution was not freshly prepared.

    Any two of the following: 1. The apparatus was not air-tight: the cork was loose or not sealed (for example with vaseline), so air leaked into the flask and the pressure inside did not fall. 2. The KOH solution was not freshly prepared, so it could not absorb the carbon dioxide given out by the seeds. 3. The seeds were dry or dead (not germinating), so they did not respire actively and gave out little or no carbon dioxide. Other correct reasons, such as the end of the delivery tube not dipping into the water, also earn credit.

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12. Q412 CBSE 2019
    A student ​is observing the temporary ​mount of ​a leaf peel ​under a ​microscope. Draw labelled diagram of the ​structure of ​stomata as seen under the microscope.
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    Draw a stoma: a pore between two kidney-shaped guard cells with chloroplasts and a nucleus, surrounded by epidermal cells.

    Labelled diagram (see the figure): the stomatal pore is a narrow opening bounded by two kidney-shaped (bean-shaped) guard cells. Each guard cell contains chloroplasts and a nucleus, and its wall facing the pore is thicker. Irregular epidermal cells, without chloroplasts, surround the guard cells. Labels: stomatal pore, guard cells, chloroplast, nucleus, epidermal cell, thick inner wall.

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13. Q413 CBSE 2019
    Identify the following diagram and name ​the parts ​marked ​as A, B and C ​:

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    The diagram shows an open stoma; A is a guard cell, B a chloroplast and C the stomatal pore.

    The diagram shows a stoma - an open stomatal pore with its two guard cells - as seen in a leaf peel under the microscope. A: Guard cell B: Chloroplast C: Stomatal pore (stoma)

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14. Q414 CBSE 2019
    In the experimental set ​up to show ​that “${\text{CO}}_2$ is given ​out during respiration”, name the substance ​taken in the small test ​tube kept in the conical flask. State its function and the consequence ​of ​its use.
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    Potassium hydroxide solution absorbs the carbon dioxide, creating a partial vacuum, so water rises in the delivery tube.

    Substance: potassium hydroxide (KOH) solution. Function: it absorbs the carbon dioxide given out by the germinating seeds during respiration. Consequence: as the ${\text{CO}}_2$ is absorbed, a partial vacuum is created in the conical flask (the pressure inside falls), so water from the beaker rises in the bent delivery tube. This shows that ${\text{CO}}_2$ is given out during respiration.

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15. Q415 CBSE 2019
    List four precautions which ​a student ​should observe while ​preparing a temporary mount ​of a leaf peel to show ​stomata in his school ​laboratory.
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    Use a thin peel, keep it in water, do not over-stain it, and lower the coverslip gently without trapping air bubbles.

    Any four of the following: (i) The leaf peel should be very small and thin (a single layer of cells). (ii) Put the peel immediately into a drop of water so that it does not dry. (iii) The peel should not be folded; spread it flat on the slide. (iv) The peel should not be overstained; wash off the extra stain. (v) Place the coverslip carefully, lowering it gently with a needle, so that no air bubbles are trapped. (Other correct precautions, such as taking the peel from the lower surface of the leaf, handling it with a brush and removing extra glycerine with blotting paper, also earn credit.)

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16. Q416 CBSE 2019
    In the experimental set-up shown,

    1. (a)name the ​material X ​filled in the small test tube ​and the material Y placed ​at the bottom of the conical flask.
    2. (b)why is there a ​rise in ​water level in the delivery tube ​?

    Show answer

    X is KOH solution, Y is germinating seeds; KOH absorbs the carbon dioxide they release, so the pressure falls and water rises.

    (a) X: potassium hydroxide (KOH) solution, which absorbs carbon dioxide. Y: germinating seeds (for example, moong or gram seeds). (b) The germinating seeds respire: they use up oxygen and give out carbon dioxide. The carbon dioxide is absorbed by the KOH solution, so the amount of gas, and hence the pressure, inside the closed flask falls. The air outside then pushes the water of the beaker up into the delivery tube. This shows that carbon dioxide is given out during respiration.

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17. Q417 CBSE 2019
    In the experiment of preparing a temporary mount of a leaf peel ​to observe stomata, we ​use two liquids ​other than water. Name ​these two liquids and ​state when and why ​these liquids ​are used.
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    Safranin, used before mounting, stains the cells so stomata are clearly seen; glycerine, used while mounting, prevents the peel from drying up.

    1. Safranin: used after the thin peel has been placed in water, before mounting (a few drops for about a minute). Why: it stains the cells, so that the guard cells and the stomata are seen clearly under the microscope. 2. Glycerine: used while mounting, as a drop on the stained peel on the slide just before the cover slip is placed. Why: it prevents the peel from drying up.

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18. Q418 CBSE 2019
    List four ​precautions ​in proper ​sequence which ​we observe ​while preparing a ​temporary ​mount of a leaf peel.
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    Keep a thin peel in water, stain it briefly, wash off the extra stain, and lower the cover slip gently without air bubbles.

    1. Take a thin peel from the lower surface of the leaf and put it in water at once, so that it does not dry or fold. 2. Stain the peel with a few drops of safranin for about a minute only; do not over-stain it. 3. Remove the extra stain by washing the peel with water or soaking it up with filter paper. 4. Put the peel on a slide with a drop of glycerine and lower the cover slip gently with a needle, so that no air bubbles are trapped. Handling the peel with a brush and keeping the slide clean are other correct precautions.

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19. Q419 CBSE 2019
    In the ​experiment ​“To prepare a temporary mount ​of a leaf peel to show stomata”, ​glycerine and safranin are used. When ​and why ​are these two liquids used ? Explain.
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    Safranin stains the cells before mounting so stomata show clearly; glycerine, added while mounting, stops the peel drying up.

    Safranin - when: after the thin peel is removed from the leaf and before it is mounted; the peel is kept in a few drops of safranin for 1 to 2 minutes and then rinsed in water. Why: it stains the cells, so the epidermal cells, the guard cells and the stomata can be seen clearly under the microscope. Glycerine - when: while mounting; a drop is put on the stained peel on the slide just before the cover slip is placed. Why: it prevents the peel from drying up during observation.

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20. Q420 CBSE 2019
    Write four ​sequential steps of ​the procedure of ​the experiment “Preparing ​a temporary ​mount ​of a leaf ​peel to ​show stomata.”
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    Take a thin peel, stain it with safranin, add glycerine, then lower a cover slip and observe under the microscope.

    (1) Take out a thin peel from the lower surface of a fresh leaf and place it in a drop of water on a clean slide. (2) Stain the peel with a drop of safranin solution; after a minute or two remove the extra stain. (3) Put a drop of glycerine on the peel. (4) Place a cover slip gently over it with the help of a needle, avoiding air bubbles, remove the extra glycerine with blotting paper, and observe the slide under the microscope.

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