Class 10 Science · Chapter 13

Our Environment

298 Class 10 Science questions on Our Environment from the NCERT textbook, NCERT Exemplar and CBSE board papers 2017–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 8 of 15

1. Q141 CBSE 2024
   Consider the following ​statements about ozone :

   1. (a)Ozone ​is ​poisonous gas.
   2. (b)Ozone ​shields the earth’s surface from the infrared radiation ​from the sun.
   3. (c)Ozone is a product of UV radiations ​acting on oxygen molecule.
   4. (d)At the lower level of the earth’s ​atmosphere, ozone performs most essential function. The correct ​statements are

   1. (a)(a) and (b)
   2. (b)(a) and (c)
   3. (c)(b) and (c)
   4. (d)(b) and (d)
   Show answer

   (b) (a) and (c)

   Step-by-step solution →
2. Q142 CBSE 2024
   Some ​wastes are given ​below ​:

   1. (i)Garden waste
   2. (ii)Ball point pen refills
   3. (iii)Empty medicine bottles ​made of glass
   4. (iv)Peels of fruits ​and vegetables
   5. (v)Old cotton shirt The non-biodegradable wastes ​among ​these are :

   1. (a)(i) and (ii)
   2. (b)(ii) and (iii)
   3. (c)(i), (iv) and (v)
   4. (d)(i), (iii) and (iv)
   Show answer

   (b) (ii) and (iii)

   Step-by-step solution →
3. Q143 CBSE 2024
   Which ​one ​of the ​following is not ​a ​natural ​ecosystem ?

   1. (a)Pond ecosystem
   2. (b)Grassland ecosystem
   3. (c)Forest ecosystem
   4. (d)Cropland ecosystem
   Show answer

   (d) Cropland ecosystem

   Step-by-step solution →
4. Q144 CBSE 2024
   Consider the following groups : i. Cotton, silk, nylon, leather ii. Wool, wood, soap, ​wheat iii. Banana, ​cat, rat, tree iv. ​Soap, detergent, silk, polyester The ​groups ​of biodegradable ​material are ​:

   1. (a)i, ii and iii
   2. (b)ii, iii and iv
   3. (c)i and iv
   4. (d)ii and iii
   Show answer

   (d) ii and iii

   Step-by-step solution →
5. Q145 CBSE 2024
   Biomagnification ​refers to ​the increase ​in ​the :

   1. (a)body weight of an organism.
   2. (b)growth of phytoplanktons.
   3. (c)the amount of harmful chemicals in the successive trophic levels of a food chain.
   4. (d)number of plants and animals in an area.
   Show answer

   (c) the amount of harmful chemicals in the successive trophic levels of a food chain.

   Step-by-step solution →
6. Q146 CBSE 2024
   In ​an ​ecosystem, ​the amount of energy of ​sunlight captured by green plants to convert ​it into ​food energy is ​:

   1. (a)90%
   2. (b)99%
   3. (c)1%
   4. (d)10%
   Show answer

   (c) 1%

   Step-by-step solution →
7. Q147 CBSE 2024
   Two ​statements are given – one ​labelled as Assertion (A) ​and the ​other labelled as Reason (R). Select the correct answer to ​these questions from the ​codes (a), (b), (c) ​and (d) as given below :

   Assertion (A): Accumulation of harmful chemicals is maximum in the organisms at the highest trophic level of a food chain.

   Reason (R): Harmful chemicals are sprayed on the crops to protect them from diseases and pests.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
   2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
   3. (c)Assertion (A) is true, but Reason (R) is false.
   4. (d)Assertion (A) is false, but Reason (R) is true.
   Show answer

   (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

   Step-by-step solution →
8. Q148 CBSE 2024
   Q. ​Nos. 17 ​to 20 ​consists of two statements – Assertion ​(A) and Reason (R), answer these ​questions ​selecting the ​appropriate option ​given below :

   Assertion (A): The waste we generate daily may be biodegradable or non-biodegradable.

   Reason (R): The waste generated, if not disposed off properly may cause serious environmental problems.

   1. (a)Both (A) and (R) are true and (R) is the correct explanation of (A).
   2. (b)Both (A) and (R) are true and (R) is not correct explanation of (A).
   3. (c)(A) is true, but (R) is false.
   4. (d)(A) is false, but (R) is true.
   Show answer

   (b) Both (A) and (R) are true and (R) is not correct explanation of (A).

   Step-by-step solution →
9. Q149 CBSE 2024
   Q. ​17 to ​20 consists ​of two statements – Assertion (A) ​and Reason (R), answer these questions ​selecting the appropriate ​option given below :

   Assertion (A): Producers are capable of using light energy from the sun to make food available in an ecosystem.

   Reason (R): All food chains in an ecosystem start with a producer.

   1. (a)Both (A) and (R) are true and (R) is the correct explanation of (A).
   2. (b)Both (A) and (R) are true and (R) is not correct explanation of (A).
   3. (c)(A) is true, but (R) is false.
   4. (d)(A) is false, but (R) is true.
   Show answer

   (b) Both (A) and (R) are true and (R) is not correct explanation of (A).

   Step-by-step solution →
10. Q150 CBSE 2024
    For Questions number 17 to 20, two statements are given — one labelled as Assertion (A) ​and the other labelled as ​Reason (R). ​Select the correct ​answer to these ​questions from ​the codes (a), (b), (c) and (d) as ​given ​below.

    Assertion (A): Oxygen is essential for all aerobic forms of life.

    Reason (R): Free oxygen atoms combine with molecular oxygen to form ozone.

    1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
    2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
    3. (c)Assertion (A) is true, but Reason (R) is false.
    4. (d)Assertion (A) is false, but Reason (R) is true.
    Show answer

    (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).

    Step-by-step solution →
11. Q151 CBSE 2024
    Two statements are ​given — ​one labelled as Assertion ​(A) and the ​other ​labelled ​as Reason (R). Select the correct answer to ​this question from the ​codes (a), (b), (c) and (d) as given below.

    Assertion (A): Ozone layer protects the surface of the Earth from harmful UV radiations.

    Reason (R): Chlorofluorocarbons (CFCs) are responsible for depletion of ozone layer.

    1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
    2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
    3. (c)Assertion (A) is true, but Reason (R) is false.
    4. (d)Assertion (A) is false, but Reason (R) is true.
    Show answer

    (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

    Step-by-step solution →
12. Q152 CBSE 2024
    Two ​statements are given — one labelled as Assertion (A) ​and the other labelled as Reason (R). Select the ​correct ​answer to ​this question from the ​codes ​(a), (b), (c) and (d) as given below.

    Assertion (A): Green plants trap only $1\%$ of the energy of sunlight that falls on their leaves.

    Reason (R): All green plants are the producers in a food chain.

    1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
    2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
    3. (c)Assertion (A) is true, but Reason (R) is false.
    4. (d)Assertion (A) is false, but Reason (R) is true.
    Show answer

    (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

    Step-by-step solution →
13. Q153 CBSE 2024
    For ​Questions number ​17 and 20, two statements are given — one labelled as ​Assertion (A) and the other ​labelled ​as Reason (R). Select the correct answer to these ​questions from the codes (a), ​(b), ​(c) and (d) as given below.

    Assertion (A): Greater number of individuals are present in lower trophic levels of all food chains.

    Reason (R): As the amount of energy decreases at each successive trophic level, larger number of individuals are required at the lower trophic levels to support higher/next trophic levels.

    1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
    2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
    3. (c)Assertion (A) is true and Reason (R) is false.
    4. (d)Assertion (A) is false and Reason (R) is true.
    Show answer

    (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

    Step-by-step solution →
14. Q154 CBSE 2024
    Two statements are given — one ​labelled as Assertion (A) and the other labelled as Reason (R). ​Select the correct answer to this question from the ​codes (a), (b), ​(c) ​and ​(d) as given below.

    Assertion (A): Ozone (${\text{O}}_3$) is a molecule formed by the three atoms of oxygen.

    Reason (R): Ozone shields the surface of the Earth from ultraviolet (UV) radiation from the Sun.

    1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
    2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
    3. (c)Assertion (A) is true, but Reason (R) is false.
    4. (d)Assertion (A) is false, but Reason (R) is true.
    Show answer

    (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).

    Step-by-step solution →
15. Q155 CBSE 2024
    “Ozone, ​although a ​deadly ​poison, ​performs ​an essential function for the life ​on the earth.” ​Justify this statement.
    Show answer

    Ozone is poisonous if breathed, but the ozone layer absorbs harmful UV radiation, which causes skin cancer, so it protects life on Earth.

    Ozone (${\text{O}}_3$) is a deadly poison if organisms breathe it. However, at the higher levels of the atmosphere the ozone layer absorbs most of the Sun's ultraviolet (UV) radiation and so shields the earth's surface from it. UV radiation is highly damaging to organisms (it causes skin cancer in human beings), so this shielding is essential for life on the earth.

    Step-by-step solution →
16. Q156 CBSE 2024
    Name the term ​used for the ​materials which cannot ​be broken down ​by ​biological processes. Give two ways ​by ​which they harm various components of an ecosystem.
    Show answer

    They are called non-biodegradable substances; they persist and pollute soil and water, and some, like pesticides, magnify along food chains.

    Such materials are called non-biodegradable substances. Two ways in which they harm the components of an ecosystem: (1) They are not broken down by decomposers, so they persist in the environment for a long time and accumulate in the soil and in water bodies, polluting them. (2) Some of them, such as pesticides, enter food chains through plants and, being non-degradable, get accumulated progressively at each trophic level (biological magnification), so organisms at the higher trophic levels, including human beings, receive the highest concentration.

    Step-by-step solution →
17. Q157 CBSE 2024
    What ​are ​decomposers ​? List two ​consequences of ​their ​absence ​in an ecosystem.
    Show answer

    Decomposers break down dead remains and wastes; without them, dead matter would pile up and nutrients would not return to the soil.

    Decomposers are micro-organisms, such as bacteria and fungi, that break down the dead remains and waste products of organisms into simple inorganic substances, which go into the soil and are used again by plants. Two consequences of their absence: (i) the dead bodies of plants and animals and their wastes would not be broken down and would pile up in the environment; (ii) nutrients would not be returned to the soil, so the soil would not be replenished, plants would not get the materials they need, and all food chains would be affected.

    Step-by-step solution →
18. Q158 CBSE 2024
    Define the ​terms biodegradable and non-biodegradable substance. Classify ​the ​following ​items into ​these two ​categories : Newspapers, Glass bottles, Polythene bags, ​Vegetable peels
    Show answer

    Newspapers and vegetable peels are biodegradable; glass bottles and polythene bags are non-biodegradable as biological processes do not break them down.

    Biodegradable substances are those broken down by biological processes, that is, by the action of decomposers such as bacteria and fungi. Non-biodegradable substances are those not broken down by biological processes; they persist in the environment for a long time or may harm members of the ecosystem. Biodegradable: newspapers, vegetable peels. Non-biodegradable: glass bottles, polythene bags.

    Step-by-step solution →
19. Q159 CBSE 2024
    Give reasons for the ​following :

    1. (a)Food web is more stable than a food ​chain in an ecosystem.
    2. (b)​A ​food ​chain should not have more ​than four to five trophic levels.
    Show answer

    Alternative food paths make a food web stable; with only about 10% of energy passed on, chains cannot exceed four or five levels.

    (a) In a food web each organism usually has several sources of food. If one species declines, its consumers can switch to other food and the ecosystem keeps functioning, whereas in a single food chain the loss of one link cuts off the food of every level above it. (b) Only about $10\%$ of the energy at one trophic level passes on to the next; the rest is lost as heat or used in life processes. After four or five levels so little energy remains (for example, $10000$ J stored by the producers leaves only $1$ J at the fifth level) that it cannot support a further level of organisms.

    Step-by-step solution →
20. Q160 CBSE 2024
    “A ​vegetarian ​food ​habit ​helps ​in getting more ​energy.” Justify the ​statement.
    Show answer

    A vegetarian, at the second trophic level, gets about $10\%$ of the plants' energy; a meat-eater, at the third, only about $1\%$.

    In a food chain only about $10\%$ of the energy at one trophic level is passed on to the next (the ten per cent law); the rest is used in life processes or lost as heat. A vegetarian eats plants, the producers, directly and is at the second trophic level, so receives about $10\%$ of the energy stored in the plants. A person who eats the meat of a herbivore is at the third trophic level and receives only $10\%$ of $10\%$, that is about $1\%$. For example, from $1000$ J in plants a vegetarian can get about $100$ J, but a person eating a goat that ate those plants gets only about $10$ J. The shorter food chain loses less energy, so a vegetarian food habit makes more energy available.

    Step-by-step solution →