Cheat sheet · Class 12 · CBSE · Science Biology
Organisms and Populations 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 11Organisms and Populations
Population growth: exponential (J-curve) vs logistic (S-curve).
1. Population Attributes
- Birth rate, death rate, sex ratio, age pyramids (expanding, stable, declining).
- Density changes by natality, immigration (+) and mortality, emigration (−).
2. Growth Models
(exponential)
(logistic)
K = carrying capacity; r = intrinsic rate of natural increase.
3. Interactions
| Interaction | Species A | Species B | Example |
|---|---|---|---|
| Mutualism | lichens, fig–wasp | ||
| Commensalism | 0 | orchid on mango, barnacles on whale | |
| Predation | − | tiger–deer | |
| Parasitism | − | Cuscuta, lice | |
| Competition | − | − | Balanus vs Chthamalus |
| Amensalism | 0 | − | Penicillium on bacteria |
4. Key Points
- Gause's competitive exclusion principle.
- Brood parasitism: cuckoo.
- Resource partitioning allows coexistence.
- Allen's rule: shorter limbs in cold climates.
Remember: Attributes | J vs S curve | interaction table
Organisms and Populations: questions and notes
More Class 12 · CBSE · Science Biology cheat sheets
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