In-text Questions — Biodegradable and Non-biodegradable Waste — Our Environment

1. 13 marksNCERT Cl-10 Science, In-text Q after Activity 13.6

   Why are some substances biodegradable and some non-biodegradable?

   Hint. Think about how specific the enzymes that break down a substance need to be.

   Step 1 — Recall how enzymes work. Enzymes are specific in their action — a particular enzyme can break down only a particular kind of substance.

   Step 2 — Apply this to natural materials. Naturally occurring materials, like food scraps, paper and cotton, can be broken down by the enzymes of decomposer bacteria and fungi, since these organisms have evolved enzymes matched to those substances — this makes them biodegradable.

   Step 3 — Apply this to human-made materials. Many human-made materials, such as plastics, aren't acted upon by any decomposer's enzymes, so they aren't broken down biologically at all — only slow physical processes like heat and pressure act on them, which is why they're called non-biodegradable.

   ✦ Answer: Whether a substance is biodegradable depends on whether decomposer organisms have enzymes that match it — natural materials do, so they're broken down; many human-made materials like plastic don't have a matching enzyme, so they persist instead.

   Where students slip. Explaining this purely in terms of 'natural vs synthetic' without the underlying reason — the real reason is enzyme specificity: decomposers simply have no enzyme capable of acting on materials like plastic.

2. 22 marksNCERT Cl-10 Science, In-text Q after Activity 13.6

   Give any two ways in which biodegradable substances would affect the environment.

   Hint. One effect is beneficial when managed well; the other happens when it isn't.

   Step 1 — Beneficial effect. Biodegradable substances decompose naturally and release nutrients back into the soil, replenishing it for plant growth.

   Step 2 — Effect when poorly managed. If allowed to accumulate in large amounts, such as when dumped together in a landfill, their decomposition can produce foul smells and greenhouse gases like methane, since anaerobic breakdown in a densely packed heap works differently from open composting, and can pollute nearby water sources if the liquid released as they decompose seeps into the ground.

   ✦ Answer: They replenish soil nutrients as they decompose, but if left to accumulate untreated, their decomposition can also produce methane and foul-smelling, polluting run-off.

   Where students slip. Assuming biodegradable waste is always harmless — even biodegradable waste needs proper management, since decomposing it in bulk without care still has environmental effects.

3. 32 marksNCERT Cl-10 Science, In-text Q after Activity 13.6

   Give any two ways in which non-biodegradable substances would affect the environment.

   Hint. One effect is about how long they last; the other is about direct harm to organisms.

   Step 1 — Persistence. Non-biodegradable substances persist in the environment for a very long time, sometimes hundreds of years, since no biological process breaks them down — so they accumulate as ever-growing waste.

   Step 2 — Direct harm. They can harm the organisms of the ecosystem directly, for example by choking or injuring animals that ingest them, or, if they are chemicals like pesticides, by undergoing biological magnification and building up to harmful concentrations higher up the food chain.

   ✦ Answer: They persist for a very long time without breaking down, and can directly harm organisms — either physically (ingestion, choking) or, for non-biodegradable chemicals, through biological magnification up the food chain.

   Where students slip. Naming only the persistence effect — the direct/biological harm to organisms in the ecosystem is an equally important second effect this question is asking for.

Solutions written by the tuition.in editorial team and checked against the NCERT Class 10 Science textbook, Reprint 2026-27 (jesc113.pdf) — three in-text question sets (7 questions total) plus one end-of-chapter Exercise (9 questions, not the 8/13 an older manifest claimed). The chapter's own core content (ecosystems, food chains/webs, trophic levels, the 10% energy rule, biological magnification, ozone depletion, biodegradable/non-biodegradable waste) is intact. A fabricated fifth trophic level and an unverified 'Lindeman (1942)' name-drop were removed from the chapter page; content on the Chipko Movement, forest/wildlife conservation and India's environmental laws — which belongs to 'Sustainable Management of Natural Resources', the old Chapter 16 dropped entirely from the current 13-chapter book — was moved to the appendix.. Questions are referenced from the NCERT textbook for identification.