Environment and Biodiversity
Environment and Biodiversity tests biodiversity at genetic, species and ecosystem levels; threats such as habitat loss, invasive species, pollution and climate change; and conservation strategies. STPM expects you to evaluate management options, not just define terms.
Core rules
- Biodiversity includes genetic variation within species, species richness and evenness, and ecosystem diversity.
- In situ conservation protects species in their natural habitat (reserves, national parks); ex situ conservation uses zoos, seed banks and gene banks.
- Pollution can be point-source or diffuse; eutrophication follows nutrient enrichment and causes algal blooms and oxygen depletion.
- Greenhouse gases absorb and re-emit infrared radiation; ozone depletion is caused mainly by CFCs and increases UV exposure.
- Sustainable management uses renewable resources at a rate that allows replacement and maintains ecosystem services.
Worked example
A community has 50 individuals of species A, 30 of B and 20 of C (N = 100). Simpson’s index D = 1 − Σ(n/N)² = 1 − (0.50² + 0.30² + 0.20²) = 1 − (0.25 + 0.09 + 0.04) = 0.62. Reasoning: D rises as evenness increases; a community dominated by one species has a lower D. Compare indices only when sampling effort and area are comparable.
Traps
- Species richness counts species; evenness describes relative abundance.
- The greenhouse effect is not the same as ozone depletion.
- Conservation is not the same as preservation; sustainable use can be part of conservation.