CBSE Class 10 Biology Our Environment MCQs Set 12

Practice MCQs for Class 10 Science Chapter 13 Our Environment

Access targeted multiple-choice questions for Chapter 13 Our Environment designed to align with the latest CBSE academic syllabus for Class 10 Science. These objective practice sets help students evaluate their conceptual understanding and improve exam readiness.

Access Chapter 13 Our Environment Questions and Solutions

Access the complete set of multiple-choice questions for Chapter 13 Our Environment below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official CBSE textbooks.

This page gives 30 exam style Our Environment MCQs for Class 10 Science with answers, short explanations and Teacher's Notes. It revises ecosystems, trophic levels, pesticide accumulation, waste disposal methods and the protection of the ozone layer.

Multiple Choice Questions

Question 1: Ozone layer is essential because it absorbs most of the
(a) infrared radiations
(b) heat
(c) solar radiation
(d) ultraviolet-radiation
Show Answer & Explanation

Answer: (d) ultraviolet-radiation

Explanation:
1. The ozone layer absorbs harmful ultraviolet radiation from the Sun.
2. Ozone in the stratosphere shields the Earth's surface from the Sun's UV rays, which can cause skin cancer.

Teacher's Note:
1. Ozone acts like a protective umbrella.
2. Do not confuse UV with infrared radiation.

Question 2: Rag pickers remove
(a) plastic, polythene, paper and metal wastes
(b) rags, cardboard, glass articles
(c) both (a) and (b)
(d) food articles.
Show Answer & Explanation

Answer: (c) both (a) and (b)

Explanation:
1. Rag pickers remove plastic, polythene, paper, metal, rags, cardboard and glass for recycling.
2. Both (a) and (b) describe the dry recyclable items that rag pickers collect, so (c) is correct.

Teacher's Note:
1. Rag pickers help the environment by sending waste for recycling.
2. Waste segregation makes their work safer.

Question 3: If a grasshopper is eaten by a frog, then the energy transfer will be from
(a) producer to decomposer
(b) producer to primary consumer
(c) primary consumer to secondary consumer
(d) secondary consumer to primary consumer
Show Answer & Explanation

Answer: (c) primary consumer to secondary consumer

Explanation:
1. The grasshopper is a primary consumer and the frog a secondary consumer.
2. Grasshopper eats plants (primary consumer) and the frog eats the grasshopper (secondary consumer).

Teacher's Note:
1. Name each organism's level before answering.
2. Energy moves in the direction of eating.

Question 4: Matter and energy are two fundamental inputs of an ecosystem. Movement of
(a) Energy is bidirectional and matter is repeatedly circulating.
(b) Energy is repeatedly circulation and matter is unidirectional.
(c) Energy is unidirectional and matter is repeatedly circulating.
(d) Energy is multidirectional and matter is bidirectional.
Show Answer & Explanation

Answer: (c) Energy is unidirectional and matter is repeatedly circulating.

Explanation:
1. Energy flows in one direction while matter circulates.
2. Matter is recycled by decomposers, but energy lost as heat cannot be reused.

Teacher's Note:
1. Energy is not recycled.
2. Matter keeps going round.

Question 5:
Assertion (A): A network of food chains existing together in an ecosystem is known as food web.
Reason (R): An animal like kite cannot be a part of a food web.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (c) A is true, but R is false.

Explanation:
1. A kite can be part of a food web, so the reason is false.
2. A food web is a network of food chains, and a kite, as a bird of prey, takes part in it.

Teacher's Note:
1. Check the reason as a separate fact.
2. Top birds also belong to food webs.

Question 6: _________ are producers.
(a) Amoeba
(b) Mushrooms
(c) Sunlight
(d) Green plants
Show Answer & Explanation

Answer: (d) Green plants

Explanation:
1. Green plants are producers.
2. Amoeba and mushrooms are consumers or decomposers and sunlight is not an organism.

Teacher's Note:
1. Producers make their own food.
2. Only green plants and some bacteria do so.

Question 7: A large number of food chains are interconnected because the organisms at the higher trophic level can depend on different types of organisms at the lower trophic level. The existence of this phenomenon in nature is called:
(a) food chain
(b) ecological balance
(c) ecological pyramid
(d) food web
Show Answer & Explanation

Answer: (d) food web

Explanation:
1. Interconnected food chains form a food web.
2. When organisms depend on several food sources, chains join into a food web.

Teacher's Note:
1. Many connections mean a web.
2. A single line means a chain.

Question 8: Excessive exposure of humans to UV rays results in :
(i) damage to immune system
(ii) damage to lungs
(iii) skin cancer
(iv) peptic ulcers
(a) (i), (ii)
(b) (ii), (iv)
(c) (i), (iii)
(d) (iii), (iv)
Show Answer & Explanation

Answer: (c) (i), (iii)

Explanation:
1. UV exposure harms the immune system and causes skin cancer.
2. UV rays lower the immune response and cause skin cancer and cataract, but they do not cause peptic ulcers.

Teacher's Note:
1. Check the lungs and ulcers options.
2. They are not UV effects.

Question 9: In the following groups of materials, which groups contain only non-biodegradable items ?
(i) Wood, paper, leather
(ii) Polythene, detergent, PVC
(iii) Plastic, detergent, grass
(iv) Plastic, bakelite, DDT
(a) (iii)
(b) (iv)
(c) (i), (iii)
(d) (ii), (iv)
Show Answer & Explanation

Answer: (d) (ii), (iv)

Explanation:
1. Polythene, detergent, PVC, plastic, bakelite and DDT are all non-biodegradable.
2. Groups (ii) and (iv) contain only such items, while (i) and (iii) include wood, paper, leather or grass.

Teacher's Note:
1. Check each material.
2. Wood, paper and grass are biodegradable.

Question 10: Which one of the following is true for a food web?
(a) Food web does not help in stabilising the ecosystem.
(b) Secondary consumers cannot feed on other species in the event of decrease in population of prey.
(c) A food web provides alternative pathways of food availability.
(d) Food webs are straight.
Show Answer & Explanation

Answer: (c) A food web provides alternative pathways of food availability.

Explanation:
1. A food web gives alternative pathways of food.
2. Because organisms have several food choices, the web gives stability.

Teacher's Note:
1. Webs are more stable than chains.
2. Alternative food avoids starvation.

Question 11: In which of the following countries Ozone hole has appeared?
(a) Africa
(b) North America
(c) Japan
(d) Antarctica
Show Answer & Explanation

Answer: (d) Antarctica

Explanation:
1. The ozone hole appeared over Antarctica.
2. Very cold conditions and CFCs made ozone thin there.

Teacher's Note:
1. This was first reported in the 1980s.
2. Learn this fact.

Question 12: Man-made plastics are not bio-degradable because:
(a) they are hard.
(b) bacteria and saprophytes do not contain enzymes to decompose plastics.
(c) plastics are made in industries.
(d) plastics do not absorb water.
Show Answer & Explanation

Answer: (b) bacteria and saprophytes do not contain enzymes to decompose plastics.

Explanation:
1. Bacteria and saprophytes lack enzymes to decompose plastics.
2. Enzymes are specific, so plastic persists.

Teacher's Note:
1. Plastics need special treatment.
2. Reduce their use.

Question 13: Which amongst the following are hazardous for the environment?
I. Pesticides
II. Fertilisers
III. Heavy metals
IV. Manures
(a) I, II and IV
(b) I and II
(c) I, II and III
(d) Only IV
Show Answer & Explanation

Answer: (c) I, II and III

Explanation:
1. Pesticides, fertilisers and heavy metals harm the environment; manure does not.
2. Manure is natural and biodegradable, so only I, II and III are hazardous.

Teacher's Note:
1. Chemicals are the problem.
2. Natural manure is safe.

Question 14:
Assertion (A): The autotrophs are at the first trophic level.
Reason (R): Autotrophs fix up the solar energy and make it available for consumers.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Autotrophs fix solar energy and give it to consumers.
2. Both statements are true and the reason explains the assertion.

Teacher's Note:
1. Producers are first.
2. They make energy available to others.

Question 15: Consider the chemical reactions taking place at upper atmosphere:
A → B + [O]; O + A → C
Here, A is the oxygen molecule (O2) which is acted upon by B to give free oxygen atoms. Select the row containing the correct naming of A, B and C.
(a) A: Molecular oxygen; B: Ultraviolet radiations; C: Ozone molecule
(b) A: Molecular oxygen; B: Infrared radiations; C: Ozone molecule
(c) A: Free oxygen; B: Ultraviolet radiations; C: Molecular oxygen
(d) A: Ozone; B: Infrared radiations; C: Molecular oxygen
Show Answer & Explanation

Answer: (a) A: Molecular oxygen; B: Ultraviolet radiations; C: Ozone molecule

Explanation:
1. A is O2, B is UV radiation and C is ozone.
2. UV splits O2 into O atoms and O + O2 gives O3.

Teacher's Note:
1. Match to the equation.
2. UV is needed.

Question 16:
Assertion (A): Omnivores receive 10% of their energy from the trophic level below them.
Reason (R): An omnivore is always in the trophic level just above herbivores.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (c) A is true, but R is false.

Explanation:
1. Omnivores can be at more than one level, so R is false.
2. A is true: 10% of energy passes up. R is false because an omnivore can also be above carnivores.

Teacher's Note:
1. Omnivores eat plants and animals.
2. They do not occupy one fixed level.

Question 17: An ecosystem includes
(a) all living organisms
(b) non-living objects
(c) both living organisms and non-living objects
(d) sometimes living organisms and sometimes non-living objects
Show Answer & Explanation

Answer: (c) both living organisms and non-living objects

Explanation:
1. An ecosystem includes living and non-living objects.
2. Both biotic and abiotic parts interact in it.

Teacher's Note:
1. Remember both components.
2. Neither alone is an ecosystem.

Question 18: Which of the following is an abiotic component of an ecosystem?
(a) Bacteria
(b) Plants
(c) Fungi
(d) Humus
Show Answer & Explanation

Answer: (d) Humus

Explanation:
1. Humus is non-living.
2. Bacteria, plants and fungi are living.

Teacher's Note:
1. Humus is dead organic matter.
2. It is abiotic.

Question 19: Complete the given analogy.
Non-biodegradable : _________ :: Biodegradable : Livestock wastes
(a) Cotton
(b) Grass
(c) Glass
(d) Orange peel
Show Answer & Explanation

Answer: (c) Glass

Explanation:
1. Glass is non-biodegradable while livestock waste is biodegradable.
2. Cotton, grass and orange peel decay.

Teacher's Note:
1. Pick the non-degradable item.
2. Analogy needs the opposite.

Question 20:
Assertion (A): The burning of substances at higher temperature to form ash is called incineration.
Reason (R): Incineration greatly reduces the volume of waste.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

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

Explanation:
1. Incineration reduces the volume of waste.
2. Both are true but the reason is not the definition.

Teacher's Note:
1. Check the explanation.
2. Learn what incineration is.

Question 21: What must be preserved in an ecosystem, if the system needs to be maintained?
(a) producers and carnivores
(b) producers and decomposers
(c) Carnivores and decomposers
(d) Herbivores and carnivores
Show Answer & Explanation

Answer: (b) producers and decomposers

Explanation:
1. Producers and decomposers are essential for energy flow and recycling.
2. Producers capture energy and decomposers recycle nutrients.

Teacher's Note:
1. Both are indispensable.
2. Others can change.

Question 22:
Assertion (A): Decomposers keep the environment clean.
Reason (R): They recycle matter by breaking down the organic remains and waste products of plants and animals.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Decomposers keep the environment clean by recycling matter.
2. Both are true and the reason explains the assertion.

Teacher's Note:
1. They break organic remains.
2. Nutrients return to soil.

Question 23: All the interacting organisms in area together with the abiotic constituents of the environment form
(a) Community
(b) Ecosystem
(c) Decomposers
(d) Parasites
Show Answer & Explanation

Answer: (b) Ecosystem

Explanation:
1. Interacting organisms and abiotic constituents form an ecosystem.
2. A community has only organisms.

Teacher's Note:
1. Both parts make an ecosystem.
2. Think of a pond.

Question 24: Consider the following food chain. Identify which of the following can be placed at X.
Grass → X → Frog → Snake → Eagle
(a) Grasshopper
(b) Rabbit
(c) Phytoplankton
(d) Rat
Show Answer & Explanation

Answer: (a) Grasshopper

Explanation:
1. Grasshopper eats grass and is eaten by frog.
2. Rabbit and rat would not fit this chain; phytoplankton is aquatic.

Teacher's Note:
1. Match habitat.
2. Insects eat grass.

Question 25: In the following food chain who gets more energy than the tertiary consumer and less energy than the primary consumer?
Grass → Grasshopper → Frog → Snake → Eagle
(a) Grasshopper
(b) Frog
(c) Snake
(d) Eagle
Show Answer & Explanation

Answer: (b) Frog

Explanation:
1. The frog has less energy than the grasshopper and more than the snake.
2. Energy decreases up the chain.

Teacher's Note:
1. Order the levels.
2. Grasshopper, frog, snake.

Question 26: Plastic bags, polyethene bags, chemicals are examples of ________ waste
(a) Non-biodegradable
(b) Biodegradable
(c) Both (A) & (B)
(d) None of these
Show Answer & Explanation

Answer: (a) Non-biodegradable

Explanation:
1. Plastic bags are non-biodegradable.
2. Chemicals also are.

Teacher's Note:
1. Plastic persists.
2. Avoid it.

Question 27: Detergent is the example of substances that are
(a) Biodegradable
(b) Non-biodegradable
(c) Ecofriendly
(d) Both (A) & (B)
Show Answer & Explanation

Answer: (b) Non-biodegradable

Explanation:
1. Detergent is non-biodegradable.
2. It persists in water.

Teacher's Note:
1. It pollutes water.
2. Persistent.

Question 28: In 1987, which programme succeeded in forging an agreement to freeze CFC production at 1986 level.
(a) UNEP
(b) UNGP
(c) AEP
(d) None of these
Show Answer & Explanation

Answer: (a) UNEP

Explanation:
1. UNEP made the 1987 agreement.
2. It froze CFC production at 1986 levels.

Teacher's Note:
1. Remember UNEP.
2. Montreal agreement.

Question 29:
Assertion (A): Each ecosystem contain only biotic components.
Reason (R): The autotrophs synthesize food material while heterotrophs utilise and resynthesize it.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation

Answer: (d) A is false, but R is true.

Explanation:
1. Ecosystems have biotic and abiotic parts.
2. A is false; R is true.

Teacher's Note:
1. Both parts.
2. Not only living.

Question 30: The human made synthetic chemical used in refrigerator is
(a) LPG
(b) CFC
(c) CH4
(d) PVC
Show Answer & Explanation

Answer: (b) CFC

Explanation:
1. CFC is the human-made refrigerant chemical.
2. LPG and CH4 are fuels.

Teacher's Note:
1. CFC harms ozone.
2. Remember it.

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