Our Environment — Class 10 MCQs with Answers

Our Environment — important questions & MCQs with answers (Class 10 Science)

6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.

0 of 6 answered

1. Q1 of 6Easy

   In a food chain, plants are:

   APredatorsBConsumersCDecomposersDProducers
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   Answer: Producers

   Explanation: Plants make their own food via photosynthesis, so they occupy the producer level of a food chain — unlike consumers, which must eat other organisms for energy.

2. Q2 of 6Easy

   Ozone layer protects us from:

   AUltraviolet radiationBCosmic raysCVisible lightDHeat
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   Answer: Ultraviolet radiation

   Explanation: Ozone (O₃) in the stratosphere absorbs most incoming ultraviolet radiation, shielding living cells from UV-induced DNA damage; it does not block cosmic rays or visible light.

3. Q3 of 6Medium

   In the food chain: grass → grasshopper → frog → snake, the snake is at:

   

   ADecomposerBProducerCPrimary consumerDTertiary consumer
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   Answer: Tertiary consumer

   Explanation: Grass is the producer (first trophic level), the grasshopper the primary consumer, the frog the secondary consumer, so the snake that eats the frog is the tertiary consumer at the fourth trophic level.

4. Q4 of 6Medium

   Assertion (A): Ozone at the higher levels of the atmosphere performs an essential function. Reason (R): This ozone shields the surface of the earth from ultraviolet (UV) radiation from the Sun.

   ABoth A and R are true and R is the correct explanation of ABBoth A and R are true but R is not the correct explanation of ACA is true but R is falseDA is false but R is true
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   Answer: Both A and R are true and R is the correct explanation of A

   Explanation: Both are true. Shielding the earth from damaging UV radiation is the essential function the chapter gives for ozone high up.

5. Q5 of 6Hard

   Depletion of ozone layer leads to:

   AAcid rainBMore oxygen in the airCLess UV reaching Earth's surfaceDMore UV reaching Earth's surface
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   Answer: More UV reaching Earth's surface

   Explanation: A thinner ozone layer lets more ultraviolet radiation reach the surface, raising risks of skin cancer, eye damage and harm to crops and marine life — far more than just one effect.

6. Q6 of 6Hard

   Assertion (A): In a food chain, human beings tend to have the highest concentration of non-degradable pesticides in their bodies. Reason (R): These chemicals are not degradable, so they build up at each trophic level, and humans occupy the top level.

   ABoth A and R are true and R is the correct explanation of ABBoth A and R are true but R is not the correct explanation of ACA is true but R is falseDA is false but R is true
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   Answer: Both A and R are true and R is the correct explanation of A

   Explanation: Both are true. The chapter explains biological magnification this way: the chemicals accumulate step by step, so the top level, humans, gets the most.

Our Environment notes: key concepts (Class 10 Science)

Living organisms and their surroundings form ecosystems in which energy flows one way and matter is recycled. This chapter covers food chains and trophic levels, the accumulation of harmful chemicals, and the two environmental problems of ozone depletion and waste management.

Ecosystem

A unit made of all the organisms in an area together with their non-living surroundings, interacting as a system.

Biotic and abiotic components

Biotic components are the living organisms; abiotic components are physical factors such as light, temperature, water and soil.

Producers

Green plants and some bacteria that make their own food by photosynthesis and support every other organism in the ecosystem.

Consumers

Organisms that depend on others for food, classed as herbivores, carnivores, omnivores and parasites.

Decomposers

Microorganisms that break down dead remains, returning nutrients to the soil and completing the cycle of matter.

Food chain

A series of organisms through which energy passes by eating, each step forming a trophic level.

Food web

The network formed by interlinked food chains, which reflects real ecosystems better than a single chain.

Trophic levels and the ten per cent law

Only about ten per cent of the energy at one trophic level passes to the next, the rest being lost mainly as heat.

Why food chains are short

Because so little energy passes on at each step, food chains rarely exceed four trophic levels.

Energy flow is unidirectional

Energy enters as sunlight and is lost as heat, never returning — unlike matter, which is recycled.

Biomagnification

The increasing concentration of harmful non-biodegradable chemicals such as pesticides at successive trophic levels, worst at the top.

Biodegradable and non-biodegradable

Biodegradable substances are broken down by microorganisms; non-biodegradable ones persist and accumulate as pollution.

Ozone layer and its depletion

Ozone in the upper atmosphere absorbs harmful ultraviolet radiation; chlorofluorocarbons break it down, thinning the layer.

Waste management and pollution

Segregating waste, reducing non-biodegradable use and treating sewage limit the pollution of land, water and air.