Class 10 Science Chapter 13 Our Environment Revision Notes

Class 10 Science Chapter 13 – Our Environment: Quick Revision Notes

• Ecosystem = biotic community (living organisms) + abiotic environment (air, water, soil, sunlight, temperature) interacting together
• Producers (green plants, algae) → capture solar energy via photosynthesis; start every food chain
• Consumers: herbivores (primary), carnivores that eat herbivores (secondary), carnivores that eat other carnivores (tertiary/top)
• Decomposers (bacteria, fungi) break down dead organic matter into simple inorganic substances, recycling nutrients back to producers
• Trophic level = each successive feeding step in a food chain (producer = level I, and so on)
• 10% law: only about 10% of energy at one trophic level passes to the next; the rest is lost mainly as heat — this is why food chains are short (rarely more than 4-5 levels)
• Food web = many interconnected food chains in an ecosystem; more stable than a single food chain
• Biodegradable waste: broken down by decomposers (vegetable peel, paper, cotton, wood)
• Non-biodegradable waste: cannot be broken down by decomposers (plastic, polythene, DDT, glass); persists and accumulates
• Biological magnification: non-biodegradable, harmful chemicals (e.g. pesticides like DDT) increase in concentration at each successive trophic level, reaching the highest levels in top consumers
• Ozone (O₃) layer: in the stratosphere, absorbs harmful solar UV radiation; ground-level ozone is a pollutant
• Ozone depletion: caused mainly by CFCs (chlorofluorocarbons); linked to skin cancer, cataracts, and harm to plants/plankton; addressed internationally via the Montreal Protocol/UNEP
• Waste management: reduce, reuse, recycle; segregate biodegradable (wet) and non-biodegradable (dry) waste at source

More on This Chapter

• NCERT Solutions – Chapter 13
• Extra Questions (HOTS) – Chapter 13
• Formulas Handbook
• Class 10 Science Book (Catalog Page)

Frequently Asked Questions

What is the difference between a food chain and a food web?
A food chain shows a single, linear sequence of who-eats-whom; a food web shows multiple interconnected food chains in an ecosystem, giving a more realistic picture since most organisms eat and are eaten by more than one species.

Last Updated: September 23, 2026

Why is the flow of energy in an ecosystem always one-directional?
Energy enters an ecosystem from the Sun, is captured by producers, and flows through various trophic levels as organisms eat one another, but a large portion is lost as heat at each step — so energy is never recycled back to the Sun, unlike matter which does cycle through ecosystems.

What to Revise First (and Last) in This Chapter

Written by Satish

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