Back to Science on Exam Trends
Our Environment
Low trendapprox. 5 marksSections A/B/C — a 1-mark MCQ or assertion-reason on trophic levels, the 10% law or ozone, plus a 2–3 mark question on food chains, biological magnification or biodegradable-vs-non-biodegradable waste.
CBSE 2027 — dates, rules and official papers →Ask the tutor1In every food chain, draw the arrow pointing TOWARD the organism that eats (→ shows the direction of energy flow, Sun → producer → consumer); a reversed or missing arrow loses the mark even if the organisms are correct.
Notesformulae · proofs · mind-map — one view
Learn the 6 conceptsteach yourself first, then practise each
Ecosystem components — biotic (producers, consumers, decomposers) & abiotic1–3 marks
Classify any given organism/factor and define an ecosystem in short-answer questions.
Food chains, food webs and trophic levels1–3 marks
Build or read a chain, assign trophic levels, and tell a chain from a web.
Ten percent law of energy flow (only ~10% passes to the next level)1–3 marks
Calculate energy available up a chain and explain why chains are short (3–4 levels).
Biological magnification2–3 marks
Explain why non-biodegradable toxins concentrate most in top consumers.
Biodegradable vs non-biodegradable waste & its disposal1–3 marks
Sort given wastes into the two classes and justify the environmental impact.
Ozone-layer depletion and its cause (CFCs)1–2 marks
State ozone's protective role and how CFCs break it down.
When you’re ready — practise or test the whole topic