Biodiversity and Environmental Issues
This domain tests biodiversity levels, hotspots, conservation, pollution, biomagnification, greenhouse effects and ozone depletion.
Core rules
- Biodiversity has genetic, species and ecosystem levels.
- Biodiversity hotspots have high species richness and high endemism with habitat loss.
- In situ conservation keeps species in natural habitat, as in national parks and biosphere reserves; ex situ conservation uses zoos, seed banks and botanical gardens.
- Pollution indicators include BOD, eutrophication and biomagnification of persistent toxins such as DDT.
- Greenhouse gases trap heat; CFCs destroy stratospheric ozone.
Worked example
If a persistent pesticide is 0.01 ppm in water, 0.1 ppm in small fish, 1 ppm in large fish and 10 ppm in fish-eating birds, each trophic level shows about tenfold biomagnification. The reasoning is that the toxin is stored in fat and not excreted, so concentration rises up the food chain. This is why top predators face the greatest toxic risk.
Traps
- A biodiversity hotspot is not defined by species number alone; endemism and threat matter.
- Ozone depletion and global warming are different problems with different causes.
- Ex situ conservation removes organisms from natural habitat.
- Eutrophication initially increases nutrients but later causes oxygen depletion.