Where Mindful Learning Begins
Where Mindful Learning Begins
Class 10 Science NCERT Solutions Chapter 13 (CBSE 2026-27) — every in-text question, every embedded Activity question, and all 9 back-of-chapter Exercises on this one page, solved with full reasoning.
Our Environment is the final chapter of Class 10 Science, and it steps back to look at how everything living and non-living around us fits together. It builds from ecosystems and their biotic and abiotic components, through producers, consumers and decomposers, food chains, food webs and trophic levels, and the 10% rule that limits how much energy actually reaches the top of a food chain — including how this same pathway lets harmful chemicals like pesticides accumulate through biological magnification. The chapter closes with two environmental problems examined closely: the depletion of the ozone layer, and how we manage the biodegradable and non-biodegradable waste we generate. These NCERT solutions work through every Activity-based conceptual question and the full 9-question Exercise set in detail.
Our Environment closes out Class 10 Science by zooming out from individual organisms to the whole system they live in. It starts with the idea of an ecosystem — biotic (living) and abiotic (non-living) components interacting together — and the three functional roles within it: producers (green plants, who capture the Sun's energy), consumers (who eat producers or other consumers), and decomposers (who break down dead organic matter and recycle it back into the soil). From there it builds food chains into trophic levels, explains why energy loss at each step (only about 10% passes on) limits food chains to just three or four levels, and shows how the same pathway that carries energy upward also lets non-biodegradable pesticides accumulate more and more at each level — biological magnification — which is why humans, near the top of most food chains, end up with the highest concentrations. The chapter's final stretch looks at two real environmental problems in detail: the ozone layer, which shields the Earth from harmful UV radiation and has been damaged by chemicals like CFCs, and the growing challenge of managing biodegradable versus non-biodegradable waste. Every question woven through the chapter is solved here, section by section, in the order the textbook presents it: all seven "QUESTIONS" spread across the chapter, the questions embedded directly inside the Activities, and the full 9-question Exercise set at the end.
Producers, consumers and decomposers; food chains, food webs, trophic levels, and how energy flows (and is lost) through them.
How non-biodegradable pesticides enter the food chain and become more concentrated at each successive trophic level.
Why the ozone layer matters, what's damaging it, and the difference between biodegradable and non-biodegradable waste.
A trophic level is each step or level in a food chain at which organisms feed and transfer energy.
Example: Grass → Goat → Human
Decomposers (bacteria and fungi) break down the dead remains and waste products of organisms into simple inorganic substances. These substances go back into the soil and are reused by plants (producers). Decomposers thus recycle nutrients back into the ecosystem, cleaning up dead organic matter that would otherwise accumulate.
Enzymes are specific in their action — a particular enzyme can only break down a particular type of substance. Natural substances (like food, plant/animal matter) can be broken down by the enzymes of bacteria and other decomposers, making them biodegradable. Many human-made materials, like plastics, have no matching enzymes in nature that can break them down, so they are non-biodegradable and persist in the environment for a very long time.
Ozone (O3) is a molecule made of three oxygen atoms. At ground level it is a poisonous gas, but at the higher levels of the atmosphere, it forms a protective layer that shields the Earth's surface from harmful ultraviolet (UV) radiation from the Sun. This UV radiation is highly damaging to organisms — it is known to cause skin cancer in humans, and can harm other living things and ecosystems. So the ozone layer protects ecosystems, and its depletion is a serious environmental concern.
An aquarium is a small, closed, human-made ecosystem — waste from fish, uneaten food, and dead plant/animal matter build up, and without enough decomposers or a large enough system to process this waste, it needs to be cleaned periodically to keep the water and environment healthy for the organisms in it.
Ponds and lakes generally do not need this kind of manual cleaning, because they are much larger, more complex, self-sustaining natural ecosystems with a full community of decomposers, plants, and other organisms that naturally recycle waste and maintain balance — though heavily polluted natural water bodies can still need intervention.
Without decomposers, garbage and the dead remains of organisms would not break down — they would simply accumulate in the environment over time, since nothing would convert them into simple substances the soil could reuse. As a result, the natural replenishment of soil nutrients would not take place, and plants would have far less of the recycled nutrients they depend on for growth.
Example chain: Algae/aquatic plants (producers) → small fish/snails (herbivores) → larger fish (carnivores).
Yes — the producers (algae/aquatic plants) can be considered of primary importance, because they are the only organisms that capture energy directly from sunlight and make it available to every other organism in the chain; without producers, none of the consumers at higher levels would have any energy source at all.
Pesticides in ready-made food items usually come from the crops (grains, fruits, vegetables) used as raw ingredients, which were sprayed with pesticides during farming — residues can survive processing. Yes, pesticides can enter our bodies through many other food products too, such as fresh fruits, vegetables, grains, and even meat and dairy (since pesticide residues can build up through the food chain).
Ways to reduce intake: thoroughly washing fruits and vegetables before eating, preferring organically grown produce where possible, peeling fruits/vegetables where appropriate, and supporting stricter regulation and testing of pesticide residue limits in food.
Answer: (a), (c) and (d) all contain only biodegradable items (grass, flowers, leather, fruit-peels, cake, lime-juice, and wood are all biodegradable). (b) is incorrect because it includes plastic, which is non-biodegradable.
Answer: (b) Grass, goat and human — grass is eaten by the goat, and the goat is eaten by the human, forming a valid feeding relationship. The others don't: (a) all three are producers; (c) all three are herbivores, none eats another; (d) a goat doesn't eat fish.
Answer: (d) All of the above.
The trophic level above it would lose its food source, and its organisms would starve, die out, or be forced to migrate. At the same time, the trophic level below it (no longer being consumed/kept in check) would grow uncontrollably in population. This disrupts the balance of the entire ecosystem and the flow of energy through the food chain.
Yes, the impact would differ by level. Removing producers (the first trophic level) would be the most catastrophic, since every other level depends directly or indirectly on them for energy — the entire food chain would collapse. Removing a higher level (like tertiary consumers) would still disrupt the balance, but the effect would ripple differently through the ecosystem. No trophic level can be removed without causing some damage — all levels are interdependent, and removing any one disrupts the balance and energy flow of the ecosystem.
Biological magnification is the phenomenon in which harmful, non-biodegradable chemicals (like pesticides) that enter a food chain get progressively more concentrated as they move up through successive trophic levels, since they accumulate in organisms' bodies rather than being broken down or excreted.
Yes, the level of magnification differs across trophic levels — the concentration of these chemicals increases at each successive level, so organisms at the top of a food chain (often humans) end up with the highest concentration of these harmful substances in their bodies.
No, even fully biodegradable waste can still impact the environment. If generated in very large quantities — faster than decomposers can break it down — it can accumulate, causing bad odour, unsanitary conditions, and attracting disease-carrying pests. Decomposition of large amounts of organic waste can also deplete oxygen in water bodies (if dumped there) and release greenhouse gases like methane, contributing to pollution. So even biodegradable waste needs to be managed properly.
The ozone layer shields the Earth's surface from harmful ultraviolet (UV) radiation from the Sun, which is known to cause skin cancer in humans and can damage other organisms and ecosystems. Damage to the ozone layer means more UV radiation reaches the Earth's surface, posing serious health and environmental risks.
Steps taken: in 1987, the United Nations Environment Programme (UNEP) forged an international agreement to freeze the production of ozone-depleting chemicals like chlorofluorocarbons (CFCs) at 1986 levels. It is now mandatory for manufacturing companies worldwide to produce CFC-free refrigerators and appliances, to help limit further damage.
That's all 13 chapters of Class 10 Science NCERT Solutions — from Chemical Reactions and Equations through to Our Environment. Revisit any chapter, browse the Class 10 Science hub, or book a free demo class for personalised coaching.
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