Chapter 13: Our Environment
Simple, exam-focused CBSE Class 10 Science notes — star topics, concepts, common mistakes, and previous year question patterns, all on one page.
Chapter 13: Our Environment
⭐ Star Topics / Most Important
- Ecosystem components and food chains
- Trophic levels and 10% law
- Ozone layer depletion
- Waste management (biodegradable vs non-biodegradable)
Detailed Chapter Notes
An ecosystem has biotic components (producers, consumers, decomposers) and abiotic components (air, water, soil, sunlight, temperature).
Producers make their own food; consumers (herbivores, carnivores, omnivores) depend on producers directly/indirectly; decomposers break down dead matter, recycling nutrients.
A food chain is a straight-line energy flow; a food web is an interconnected network of overlapping chains. Each step is a trophic level.
10% law: only ~10% of energy at one trophic level transfers to the next; rest is lost as heat during respiration and movement — this is why food chains rarely exceed 3-4 levels.
Biological magnification is increasing concentration of harmful chemicals (like DDT) up the food chain, since they don't easily break down and accumulate in fatty tissue.
Ozone layer absorbs harmful UV radiation, depleted mainly by CFCs — addressed by the Montreal Protocol. Waste management: biodegradable waste breaks down naturally; non-biodegradable waste (plastic, glass, metals) accumulates — hence Reduce, Reuse, Recycle.
A food web isn't just "more food chains drawn together" — the real point is that most organisms have multiple food sources and predators, making an ecosystem more stable. Also, when explaining the 10% law, always mention WHY energy is lost (respiration, movement, undigested food) — stating just "10% is transferred" loses half the marks.
Search on YouTube: Our Environment Class 10 food chain food web explained for a visual walkthrough of this chapter.
- What is a trophic level? Explain with an example (2 marks)
- Why is only 10% of energy transferred from one trophic level to the next? (3 marks)
- What is biological magnification? Give one example (2 marks)
- Distinguish between biodegradable and non-biodegradable substances with examples (2 marks)
- Why should decomposers be considered an essential component of an ecosystem? (2 marks, HOTS)