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SolveItNCERT · CBSE · NEET

NCERT Exemplar · Class 10 Science Our Environment

38 questions · 38 still being checked

Short Answer Questions 22–30 (part 3 of 4)

  1. Exercise 22

    Why is improper disposal of waste a curse to environment?

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    NCERT’s answer
    Wastes pollute our environment, air, soil and water, and cause harmful effects on all living organisms.
    Decomposers cannot break down non-biodegradable waste: \[\text{non-biodegradable waste} \Rightarrow \text{persists in soil and water} \Rightarrow \text{enters food chain} \] \[\text{trophic level } 1 \to 4:\ \text{toxin concentration}\uparrow \quad \text{(biomagnification)} \] Burning waste pollutes air; rotting waste breeds pathogens; plastics block drains and reduce soil aeration. Answer: Improper disposal pollutes soil, water and air, and toxins biomagnify, harming organisms and ecological balance.

  2. Exercise 23

    Write the common food chain of a pond ecosystem.

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    NCERT’s answer
    Phytoplanktons and aquatic plants → small aquatic animals larvae, insects etc) → fish → bird
    \[\text{Aquatic plants / phytoplankton} \rightarrow \text{Insect larvae} \rightarrow \text{Fish} \rightarrow \text{Kingfisher} \] \[\text{producer} \rightarrow \text{primary consumer} \rightarrow \text{secondary consumer} \rightarrow \text{tertiary consumer} \] Answer: Phytoplankton → insect larvae → fish → kingfisher.

  3. Exercise 24

    What are the advantages of cloth bags over plastic bags during shopping?

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    NCERT’s answer
    Cloth bags are
    (a)
    capable of carrying more things
    (b)
    made of biodegradable material
    (c)
    do not pollute our environment
    (d)
    can be reused
    • Biodegradable: decompose without toxic residue, while polythene persists for hundreds of years. • Reusable and stronger — carry more, so fewer bags are discarded. • Do not choke drains, soil pores or animals' guts like discarded plastic. Answer: Cloth bags are biodegradable, reusable, stronger and non-polluting; plastic bags persist and pollute.

  4. Exercise 25

    Why are crop fields known as artificial ecosystems?

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    NCERT’s answer
    Crop fields are man made and some biotic and abiotic components are manipulated by humans
    • Man-made: farmers choose the crop, then sow, weed and harvest it — humans control the biotic part. • Irrigation and fertiliser supply water and nutrients — humans control the abiotic part. • One crop species dominates, not a self-sustaining natural community. Answer: Crop fields are man-made, human-managed, near-monoculture ecosystems.

  5. Exercise 26

    Differentiate between biodegradable and non-biodegradable substances. Cite examples.

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    NCERT’s answer
    Substances that are broken down into simpler substances by biological processes are said to be biodegradable. Examples, wood, paper. Substances that cannot be broken down into simpler ones by biological processes are said to be non-biodegradable. Examples, plastic, DDT.
    Biodegradable: broken down into harmless substances by microorganisms. Examples: vegetable peels, paper, wood, cotton cloth, cow dung. Non-biodegradable: resist microbial breakdown and persist for long; persistent toxins like DDT also biomagnify. Examples: plastic, polythene, DDT, glass, metals. Answer: Biodegradable substances are decomposed by microbes (peels, paper); non-biodegradable ones persist (plastic, glass, DDT).

  6. Exercise 27

    Suggest one word for each of the following statements/ definitions
    (a)
    The physical and biological world where we live in
    (b)
    Each level of food chain where transfer of energy takes place
    (c)
    The physical factors like temperature, rainfall, wind and soil of an ecosystem
    (d)
    Organisms which depend on the producers either directly or indirectly for food

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    NCERT’s answer
    (a)
    Environment/biosphere
    (b)
    Trophic level
    (c)
    Abiotic factors
    (d)
    Consumers/heterotrophs
    (a)
    Environment (b) Trophic level (c) Abiotic components (d) Consumers
    Answer: (a) Environment (b) Trophic level (c) Abiotic components (d) Consumers

  7. Exercise 28

    Explain the role of decomposers in the environment?

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    NCERT’s answer
    Decomposers break down the dead and decaying organic matter and return the nutrients to the soil. Thus, they play a very important role in the nutrient re-cycling in the environment.
    Decomposers (bacteria, fungi) break down dead remains and waste into simple substances. \[\text{dead plants/animals, excreta} \xrightarrow{\text{decomposers}} \mathrm{CO_2,\ H_2O,\ minerals} \] These simple substances return to soil, water and air for producers to reuse, keeping nutrients cycling and the environment clean.Answer: Decomposers degrade dead organic matter and waste into simple inorganic substances, recycling nutrients back into the environment.

  8. Exercise 29

    Select the mis-matched pair in the following and correct it.
    (a)
    Biomagnification — Accumulation of chemicals at the successive trophic levels of a food chain
    (b)
    Ecosystem — Biotic components of environment
    (c)
    Aquarium — A man-made ecosystem
    (d)
    Parasites — Organisms which obtain food from other living organisms

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    NCERT’s answer
    (b)
    Is not a matching pair
    Both biotic and abiotic components of environment constitute an ecosystem
    (a), (c), (d) correctly match their terms; (b) is mismatched. An ecosystem is not just the biotic components — it is the biotic and abiotic components of an environment interacting with each other.Answer: (b) is mismatched; corrected: Ecosystem — the biotic and abiotic components of an environment interacting with each other.

  9. Exercise 30

    We do not clean ponds or lakes, but an aquarium needs to be cleaned. Why?

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    NCERT’s answer
    An aquarium is an artificial and incomplete ecosystem in contrast to a pond/lake which are natural, self-sustaining and complete ecosystems.
    Pond or lake: natural, complete and self-sustaining, so its decomposers recycle waste. \[\text{dead matter, excreta} \xrightarrow{\text{decomposers}} \text{nutrients} \rightarrow \text{producers} \] Aquarium: artificial and incomplete, with too few decomposers and no full food web. \[\text{excreta, uneaten food} \Rightarrow \text{accumulate} \Rightarrow \text{foul water} \] Answer: A pond or lake is a complete, self-sustaining natural ecosystem; an aquarium is an artificial, incomplete one, so its waste must be removed by hand.