Class 10 Science Chapter 13 (formerly Chapter 15), Our Environment, concludes the NCERT Class 10 Science book (2026-27) by examining ecosystems, producers, consumers and decomposers, food chains and food webs, the $10\%$ energy transfer law, biological magnification, ozone layer depletion, and biodegradable vs non-biodegradable waste management.
What Class 10 Science Chapter 13 Covers
13.1 Eco-system — What Are Its Components? & Food Chains and Webs classifies ecosystems into natural (forests, ponds, lakes) and artificial/human-made (gardens, crop-fields, aquariums), groups biotic components into producers, consumers (herbivores, carnivores, omnivores, parasites) and decomposers (bacteria and fungi that break down dead organic matter into simple inorganic nutrients), and traces trophic levels across food chains and branching food webs.
13.1.1 Energy Flow & Biological Magnification shows that green plants capture about $1\%$ of solar energy falling on their leaves and only about $10\%$ of organic energy is transferred to the next trophic level (limiting food chains to 3 or 4 steps) with unidirectional energy flow, while non-degradable chemicals like pesticides accumulate progressively at higher trophic levels (**biological magnification**).
13.2 How Do Our Activities Affect the Environment? explains how UV radiation forms and depletes stratospheric ozone ($\text{O}_2 \xrightarrow{\text{UV}} \text{O} + \text{O}$, $\text{O} + \text{O}_2 \rightarrow \text{O}_3$), how chlorofluorocarbons (CFCs) used in refrigerants and fire extinguishers caused the ozone hole before the 1987 UNEP freeze, and why enzymes decompose biodegradable wastes but cannot break down non-biodegradable plastics.
Exercises in Chapter 13
- In-text Questions cover why some substances are biodegradable and some are non-biodegradable, what trophic levels are, the role of decomposers in the ecosystem, and what ozone is and how it affects any ecosystem.
- Chapter Exercises (9 Questions) ask what happens if we kill all the organisms in one trophic level, whether the impact of removing all organisms in a trophic level is different for different trophic levels, and explain biological magnification.
Read Class 10 Science Chapter 13 Online
More Chapters
- Previous: Chapter 12: Magnetic Effects of Electric Current
- Hindi medium: Class 10 Science Chapter 13 PDF in Hindi (Vigyan)
- All Science chapters and the other Class 10 books: Class 10 NCERT books 2026-27
- All Class 1 to 12 NCERT Textbooks: NCERT Books PDF (Class 1–12)
FAQ
What is the 10% law of energy transfer in a food chain?
Only an average of $10\%$ of the organic matter/energy present at one trophic level reaches the next level of consumers; the remaining $90\%$ is used in metabolic processes or lost as heat to the environment. Because so little energy remains after three or four steps, food chains rarely exceed four trophic levels.
What is biological magnification?
Non-degradable harmful chemicals such as pesticides and insecticides washed into soil or water are absorbed by plants or aquatic organisms and are not metabolised or excreted. As they pass up the food chain, their concentration increases progressively at each higher trophic level, reaching maximum concentration in human beings at the top.