Cheat sheet · Class 12 · CBSE · Science Biology
Ecosystem cheat sheet
The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.
CBSE Class 12 · Biology
Cheat sheet
Chapter 12Ecosystem
10% law: only about 10% of energy passes to the next trophic level.
1. Productivity
Annual NPP of biosphere ≈ 170 billion tonnes (dry weight); oceans ~55.
2. Decomposition
Fragmentation → leaching → catabolism → humification → mineralisation.
Faster when warm and moist; slower with lignin and chitin.
3. Energy Flow & Pyramids
- Unidirectional flow; grazing and detritus food chains.
- Pyramid of energy is always upright.
- Pyramid of biomass is inverted in the sea; pyramid of numbers inverted for a tree.
4. Succession
- Primary (bare rock) vs secondary (after disturbance).
- Pioneer species: lichens (xerarch), phytoplankton (hydrarch).
- Ends in a climax community.
5. Key Points
- Producers fix only 2–10% of PAR.
- Phosphorus cycle has no gaseous phase.
- Ecosystem services: pollination, purification.
- Standing crop = biomass at a time.
Remember: GPP/NPP | decomposition steps | pyramids | succession
Ecosystem: questions and notes
More Class 12 · CBSE · Science Biology cheat sheets
- Sexual Reproduction in Flowering Plants
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- Principles of Inheritance and Variation
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- Microbes in Human Welfare
- Evolution
- Human Health and Disease
- Reproductive Health
- Biotechnology: Principles and Processes
- Biotechnology and its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
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