Ecology and Environment
Ecology and Environment covers adaptations, population growth, interactions, ecosystem function, biodiversity and pollution.
Core rules
- Population growth: exponential dN/dt = rN; logistic dN/dt = rN(K−N)/K, slowing near carrying capacity K.
- Interactions: mutualism (+/+), commensalism (+/0), parasitism (+/−), predation (+/−), competition (−/−).
- Succession: pioneer species → seral stages → climax; hydrarch starts in water, xerarch on bare rock.
- Ecosystem: gross primary productivity minus respiration = net primary productivity; energy flow follows the 10% law; decomposition steps are fragmentation, leaching, catabolism, humification and mineralisation.
- Nutrient cycles: carbon has a gaseous phase; phosphorus is sedimentary and has no gaseous phase.
- Biodiversity: hotspots, in situ conservation (national parks, sacred groves) and ex situ conservation (seed banks, zoos).
- Pollution: greenhouse gases, ozone depletion by CFCs, eutrophication, biomagnification.
Worked example
In a mark–recapture study, 80 fish are marked and released. Later, 100 fish are caught and 20 are marked. Estimated population N = (marked first × total second) / marked second = (80 × 100) / 20 = 400. The method assumes the marked animals mix randomly and are not more or less likely to be recaptured.
Traps
Do not confuse GPP with NPP. The phosphorus cycle is sedimentary. Ozone in the stratosphere is protective; tropospheric ozone is a pollutant.