LIWA

Our Environment

CBSE Class 10 · Science · Chapter 13

Past board exam questions

CBSE 2027 sample paper · 1 mark

A fish living in a pond ecosystem feeds on small aquatic insects (larvae). These insect larvae, in turn, feed on green algae and small photosynthetic bacteria. In this specific food chain, what is the trophic level classification of fish?

  1. Producer
  2. Primary Consumer
  3. Secondary Consumer
  4. Tertiary Consumer
Show answer
Secondary Consumer

CBSE 2027 sample paper · 1 mark

Assertion (A): In an ecosystem, 1% of energy is available for transfer from one trophic level to the next. Reason (R): An average of 10% of the food eaten by organisms is available for flow in the form of chemical energy.

  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, and R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
Show answer
A is false but R is true.

CBSE 2027 sample paper · 3 marks

Study the food chain given below: Phytoplankton → zooplankton → small fishes → large fish A. In the given food chain, the amount of energy available at the fourth trophic level is 10 kJ, what will be the energy available at the producer level? B. Is it possible to have three more trophic levels in the above food chain? Justify. C. Which of these trophic levels will have the maximum amount of pesticide, if it had washed down in the water body from agricultural fields. Why?

Show answer
A. Only about 10% of the energy passes from one level to the next (10% law). Fourth level (large fish) = 10 kJ, so third level = 100 kJ, second level = 1000 kJ and producer level (phytoplankton) = 10000 kJ. B. No. So much energy is lost at each step that very little usable energy would be left (10 kJ → 1 kJ → 0.1 kJ → 0.01 kJ); it could not support three more trophic levels. C. Large fish. Pesticides are non-biodegradable and are not broken down; they accumulate progressively at each trophic level (biological magnification), so the highest level, the large fish, has the maximum concentration.

CBSE 2026 board paper · 1 mark

Given below are some of the statements regarding our environment : (i) Change in our life-styles have resulted in greater amounts of waste material generation. (ii) Changes in attitude have resulted in use of more disposable things. (iii) Changes in packaging has resulted in much of our waste becoming non-biodegradable. (iv) Organic farming. Which amongst these is not leading to any damage of environment ?

  1. (i), (ii), (iii)
  2. (iv)
  3. (i) and (iii)
  4. (ii) and (iv)
Show answer
(iv)

CBSE 2026 board paper · 1 mark

An ecosystem contains maximum number of :

  1. Producers
  2. Herbivores
  3. Carnivores
  4. Omnivores
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Producers

CBSE 2026 board paper · 1 mark

Examine the given food chains to establish the correct one in an ecosystem :

  1. Seed → mouse → snake → deer
  2. Algae → small fish → large fish → hawk
  3. Grasshopper → frog → snake → elephant
  4. Plants → rabbit → deer → wolf
Show answer
Algae → small fish → large fish → hawk

CBSE 2026 board paper · 1 mark

Select the incorrect statement from the following :

  1. Ozone is a molecule formed by three atoms of oxygen.
  2. Ozone shields earth’s surface from harmful infrared radiations.
  3. CFC’s are linked to decline of O3 layer in our atmosphere.
  4. Ozone at higher levels is a product of UV radiations acting on oxygen molecule.
Show answer
Ozone shields earth’s surface from harmful infrared radiations.

CBSE 2026 sample paper · 1 mark

Which are the correct statements related to ozone? (i) Ozone layer helps in increasing the UV radiations reaching earth. (ii) Ozone is a deadly poison. (iii) Ozone layer shields the earth from UV radiations. (iv) Ozone layer prevents UV rays which cause skin cancer. (v) Ozone is formed with the help of Chloroflurocarbons.

  1. (i), (ii), (iii)
  2. (ii), (iii), (iv)
  3. (iii), (iv), (v)
  4. (i), (iv), (v)
Show answer
(ii), (iii), (iv)