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 6 of 15

1. Q101 CBSE 2025
   In the food chains given below. Select the ​most ​efficient ​food ​chain ​in terms ​of energy ​:

   1. (a)Grass → Grasshopper → Frog → Snake
   2. (b)Plants → Deer → Lion
   3. (c)Plants → Man
   4. (d)Phytoplankton → Zooplankton → Small Fish → Big Fish
   Show answer

   (c) Plants → Man

   Step-by-step solution →
2. Q102 CBSE 2025
   The ​examples ​of natural ​and ​manmade (artificial) ​ecosystems ​are respectively

   1. (a)Forests and ponds
   2. (b)Crop fields and lakes
   3. (c)Lakes and gardens
   4. (d)Crop fields and forests
   Show answer

   (c) Lakes and gardens

   Step-by-step solution →
3. Q103 CBSE 2025
   Consider the following food ​chain ​: Grass → Grasshopper → Frog → Snake → Eagle If the ​amount of energy available at third trophic ​level is 50 kJ, ​the available energy at ​the ​producer level ​was :

   1. (a)0.5 kJ
   2. (b)5 kJ
   3. (c)500 kJ
   4. (d)5000 kJ
   Show answer

   (d) 5000 kJ

   Step-by-step solution →
4. Q104 CBSE 2025
   In ​the ​following groups of wastes, which group contains ​only ​non-biodegradable ​wastes ​?

   1. (a)Leather footwear, Plastic plate, Polythene bag
   2. (b)Empty medicine bottle, Milk packet, Aluminium can
   3. (c)Used tea leaves, Cardboard box, Iron nail
   4. (d)Plastic Syringes, Newspaper, Ball point pen
   Show answer

   (b) Empty medicine bottle, Milk packet, Aluminium can

   Step-by-step solution →
5. Q105 CBSE 2025
   The ​percentage of solar energy ​which is not ​converted into ​food energy by the ​leaves of green ​plants ​in a terrestrial ecosystem is about ​:

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

   (d) $99\%$

   Step-by-step solution →
6. Q106 CBSE 2025
   Identify from the ​following ​a group ​containing ​all ​non-biodegradable ​substances.

   1. (a)Leather, Glass, Plastic
   2. (b)Cotton, Wood, Nylon
   3. (c)DDT, Polyester, Glass
   4. (d)Leather, Silk, Wool
   Show answer

   (c) DDT, Polyester, Glass

   Step-by-step solution →
7. Q107 CBSE 2025
   Other than ​the ​abiotic components, which of the given biotic components are not required to make an ​aquarium ​with small herbivorous fishes a self-sustaining system ?

   1. (i)Aquatic plants and aquatic animals
   2. (ii)Terrestrial plants and terrestrial animals
   3. (iii)​Decomposers as ​bacteria and fungi
   4. (iv)Consumers as clown ​fishes and sea urchins

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

   (d) (ii) and (iv)

   Step-by-step solution →
8. Q108 CBSE 2025
   Select ​from the following, ​a food chain ​in which the ​organism of the second trophic ​level is missing :

   1. (a)small fish, zooplankton, phytoplankton, large fish
   2. (b)frog, snake, grass, grasshopper, eagle
   3. (c)grass, frog, tiger, snake
   4. (d)grass, goat, lion
   Show answer

   (c) grass, frog, tiger, snake

   Step-by-step solution →
9. Q109 CBSE 2025
   Which ​one ​of the ​following statements is incorrect about the ​effect ​on our environment ​as a ​result of our activities ?

   1. (a)Improvement in our lifestyle has resulted in greater amounts of waste.
   2. (b)Packaging of materials has resulted in lesser amount of non-biodegradable waste.
   3. (c)Use of disposable cups/kulhads results in loss of fertile topsoil.
   4. (d)Harmful wastes that are non-biodegradable persist in the environment for a long time.
   Show answer

   (b) Packaging of materials has resulted in lesser amount of non-biodegradable waste.

   Step-by-step solution →
10. Q110 CBSE 2025
    Which one of the following ​gets biomagnified ​at ​different ​levels ​in a food chain ?

    1. (a)Carbon monoxide
    2. (b)CFC's
    3. (c)DDT
    4. (d)Manure
    Show answer

    (c) DDT

    Step-by-step solution →
11. Q111 CBSE 2025
    Human activities ​that ​are ​affecting the ​environment ​are ​:

    1. (a)minimising the use of chloroflurocarbons.
    2. (b)excessive use of disposable cups and plates.
    3. (c)maximising the use of reusable utensils for eating food and drinking fluids.
    4. (d)segregating the wastes into biodegradable and non-biodegradable before disposal.
    Show answer

    (b) excessive use of disposable cups and plates.

    Step-by-step solution →
12. Q112 CBSE 2025
    The ​incorrect statement ​about ​ozone is

    1. (a)It is a deadly poisonous gas.
    2. (b)It shields the surface of the earth from UV radiation from sun.
    3. (c)It is used as a refrigerant and in fire-extinguishers.
    4. (d)It is formed by combining oxygen molecule with free oxygen atom.
    Show answer

    (c) It is used as a refrigerant and in fire-extinguishers.

    Step-by-step solution →
13. Q113 CBSE 2025
    Green ​plants ​occupy ​the first trophic ​level in every ​food ​chain because ​they

    1. (a)exist over a large area.
    2. (b)have very less concentration of harmful chemicals.
    3. (c)have to feed large number of herbivores.
    4. (d)can synthesize food by photosynthesis.
    Show answer

    (d) can synthesize food by photosynthesis.

    Step-by-step solution →
14. Q114 CBSE 2025
    In an ecosystem, ​10% of energy available for ​transfer from one trophic level ​to the next in a food chain is in ​the ​form ​of :

    1. (a)heat energy
    2. (b)chemical energy
    3. (c)mechanical energy
    4. (d)light energy
    Show answer

    (b) chemical energy

    Step-by-step solution →
15. Q115 CBSE 2025
    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 the harmful ultraviolet radiations.

    Reason (R): Chlorofluorocarbons (CFCs) are responsible for the depletion of the ozone layer present at the higher levels of the atmosphere.

    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 →
16. Q116 CBSE 2025
    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): The amount of ozone in the atmosphere began to drop sharply in the 1980s.

    Reason (R): The 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 →
17. Q117 CBSE 2025
    Two ​statements are given ​below — 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) given below.

    Assertion (A): Use of jute bags for shopping reduces pollution.

    Reason (R): Jute is biodegradable and its bag may be reused as and when needed.

    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

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

    Step-by-step solution →
18. Q118 CBSE 2025
    Question Nos. 17 to 20 ​consists of two ​statements – Assertion (A) and Reason ​(R). Answer these questions selecting the appropriate option from ​(a), ​(b), (c) and (d) given ​below :

    Assertion (A): All organisms can make organic compounds like sugar and starch from inorganic substances using radiant energy of the sun.

    Reason (R): The organisms which can produce food by photosynthesis are called producers.

    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

    (d) Assertion (A) is false, but Reason (R) is true.

    Step-by-step solution →
19. Q119 CBSE 2025
    Two statements are given ​below – 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) given below.

    Assertion (A): Food web is a network of several food chains operating in an ecosystem.

    Reason (R): Food web decreases the stability of an ecosystem.

    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 and 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

    (c) Assertion (A) is true, but Reason (R) is false.

    Step-by-step solution →
20. Q120 CBSE 2025
    A ​gas ​‘X’ is found in ​the ​upper layer of atmosphere. It is a deadly poison, but still essential ​for all life forms on earth.

    1. (a)Identify the gas and state the main factor for its depletion in the atmosphere.
    2. (b)How is ​this gas formed in the upper atmosphere ?
    Show answer

    Gas X is ozone (${\text{O}}_3$), depleted mainly by CFCs; UV splits oxygen molecules into atoms that combine with oxygen to form ozone.

    (a) Gas X is ozone, ${\text{O}}_3$. The main factor for its depletion is chlorofluorocarbons (CFCs), synthetic chemicals used as refrigerants and in fire extinguishers. (b) In the upper atmosphere, high-energy ultraviolet (UV) radiation from the Sun splits some oxygen molecules into free oxygen atoms, ${\text{O}}_2\stackrel{\text{UV}}{\to }\text{O}+\text{O}$. Each free oxygen atom then combines with an oxygen molecule to form ozone, $\text{O}+{\text{O}}_2\to {\text{O}}_3$.

    Step-by-step solution →