Why are food chains generally limited to three or four trophic levels?
Answer framework: Apply the ten-percent law and explain progressive energy loss.
All Class 10 Science notes
Chapter 13 • Environment
Our Environment
Analyse ecosystems, food chains, trophic levels, energy flow, biomagnification, ozone depletion and responsible waste management.
Core concepts checklist
Ecosystem components
Food chains and food webs
Trophic levels and ten-percent law
Biological magnification
Ozone layer, waste and biodegradable materials
Formula & fact bank
Sun → producer → primary consumer → secondary consumer
Energy transfer ≈ 10% to next trophic level
Biomagnification increases at higher trophic levels
3Rs: Reduce, Reuse, Recycle
Diagrams to practise
Draw with pencil, use straight label lines, add arrows and write a precise caption.
- 1Food chain with trophic levels
- 2Food web
- 3Energy pyramid
- 4Ozone formation and depletion
CBSE examiner focus
- Arrows in a food chain show energy flow
- Distinguish bioaccumulation from biomagnification
- Support environmental answers with a scientific cause–effect chain
Board-style practice
Explain biological magnification and ozone depletion.
Answer framework: Define each, describe the causal pathway, state impact and give preventive action.
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