Environment and Biodiversity
What this domain tests
Questions target the levels of biodiversity, hotspots and endemism, Kerala's protected areas, in-situ versus ex-situ conservation, pollution phenomena such as biomagnification and eutrophication, and global environmental conventions.
Core rules
- Biodiversity has three levels: genetic, species and ecosystem diversity.
- A biodiversity hotspot has high species richness with many endemics and heavy habitat loss. The Western Ghats is one; Silent Valley National Park lies within it, and Eravikulam National Park protects the Nilgiri tahr.
- Kerala's Ramsar wetlands include Vembanad-Kol and Ashtamudi; mangrove species such as Rhizophora stabilise coastal mud and nurse fish.
- In-situ conservation keeps species in their habitat: national parks, wildlife sanctuaries, biosphere reserves, sacred groves. Ex-situ keeps them outside: zoos, botanical gardens, seed and gene banks, cryopreservation.
- Threats: habitat fragmentation, invasive species (water hyacinth, Lantana, African catfish), poaching, pesticide pollution, climate change.
- Biomagnification: non-degradable toxins such as DDT concentrate at successive trophic levels.
- Eutrophication from fertiliser runoff causes algal blooms, oxygen depletion and fish kills. Ozone depletion is linked to CFCs; acid rain to sulphur and nitrogen oxides; the greenhouse effect to CO2, methane and nitrous oxide.
- Legal tools: Wildlife (Protection) Act 1972, Biological Diversity Act 2002, Ramsar Convention 1971, CITES.
Worked example
A lake receives DDT at 0.001 ppm. Reasoning: the pesticide is fat-soluble and not excreted, so each trophic level retains the dose of all the prey it eats. Plankton may reach 0.04 ppm, small fish 0.5 ppm, predatory fish 2 ppm and fish-eating birds over 20 ppm - enough to thin eggshells and crash the bird population although the water itself is dilute.
Traps that cost marks
Calling any species-rich area a hotspot; mixing up in-situ and ex-situ; blaming ozone depletion for global warming; saying biomagnification dilutes toxins; naming Silent Valley as a sanctuary rather than a national park.