Ecology and Environment
Ecology and Environment covers organisms and populations, ecosystem, biodiversity and conservation, and environmental issues. The exam tests population growth, energy flow, biodiversity status, and pollution effects.
Core rules
- Population growth: exponential when resources are unlimited, Nt = N0 e^rt; logistic when resources are limited, giving an S-shaped curve with carrying capacity K.
- Ecosystem: producers fix energy; energy flow is unidirectional; the 10% law applies to energy transfer between trophic levels; nutrients cycle.
- Biodiversity: hotspots have high endemism and habitat loss. In-situ conservation includes national parks, biosphere reserves, and sacred groves; ex-situ includes zoos, seed banks, and botanical gardens. In Tamil Nadu, the Gulf of Mannar and Nilgiri are biosphere reserves.
- Environmental issues: greenhouse gases cause global warming; CFCs deplete ozone; biomagnification concentrates pollutants at higher trophic levels.
Worked example
Producers contain 1,00,000 kJ of energy. Using the 10% law, find the energy at the tertiary consumer. Reasoning: primary consumer = 10% of 1,00,000 = 10,000 kJ. Secondary consumer = 10% of 10,000 = 1,000 kJ. Tertiary consumer = 10% of 1,000 = 100 kJ.
Traps
The 10% law is about energy, not biomass or number. Exponential growth needs unlimited resources; logistic growth includes K. Sacred groves are in-situ, not ex-situ. Biomagnification increases concentration at higher trophic levels; it does not dilute. Ozone depletion and greenhouse warming are different problems.