Environment and Ecology: Energy Flow, Conservation and Pollution
Environment questions test energy flow, conservation categories, pollution and Rajasthan's desert ecology.
Ecosystem basics
- Components are producers, consumers, decomposers and the abiotic environment.
- Food chains link into food webs; at each trophic level only about 10% of energy passes on, the ten per cent law, so chains rarely exceed four or five links.
- The pyramid of energy is always upright; pyramids of number and biomass can be inverted.
Biodiversity and conservation
- In-situ conservation: national parks, wildlife sanctuaries, biosphere reserves and sacred groves. Ex-situ: zoos, botanical gardens, seed and gene banks, cryopreservation.
- IUCN categories run Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened and Least Concern.
- Rajasthan: Khejri (Prosopis cineraria) is the state tree; the Aravalli barriers the desert's spread; desertification, mining and groundwater depletion are the main threats.
Pollution
- Air pollutants include carbon monoxide, sulphur dioxide, nitrogen oxides and particulate matter. Ozone depletion by CFCs is a separate problem from global warming by carbon dioxide and methane.
- Water: BOD and COD indicate organic load; nitrate and phosphate runoff cause eutrophication.
- Soil: pesticide residues, salinity from canal seepage in the IGNP command and nitrate leaching.
Worked example
If producers fix 10,000 joules, herbivores assimilate about 1,000 joules, primary carnivores 100 joules and top carnivores 10 joules. This explains why top predators need huge territories and why long food chains cannot support viable populations.
Traps
- Applying the ten per cent law to biomass as a fixed rule.
- Mixing the greenhouse effect with ozone depletion.
- Treating a sanctuary and a national park as legally identical; the rights of local communities differ.