Ecology and Environmental Sustainability: Energy, Populations and Human Impact
Ecology and Environmental Sustainability tests interactions between organisms and their environment and how human activity alters them. Expect food webs, energy flow, nutrient cycles, population ecology, biodiversity and pollution.
Ecosystems and energy
- Habitat vs niche; population vs community vs ecosystem; biotic and abiotic factors.
- Food chain arrows show energy flow; producers fix light; consumers; decomposers recycle nutrients.
- Energy lost as heat, movement, excretion; only ~10% transfers to next trophic level; pyramids of energy always upright, numbers can invert.
- Carbon cycle: photosynthesis removes CO2; respiration, combustion, decomposition release it. Nitrogen cycle: fixation, nitrification, assimilation, denitrification.
Populations and sustainability
- Population growth affected by birth rate, death rate, immigration, emigration; carrying capacity set by limiting resources.
- Biodiversity: genetic, species, ecosystem. Threats: habitat loss, invasive species, pollution, climate change, overexploitation.
- Eutrophication: nutrients → algal bloom → death → decomposers → oxygen depletion → fish kill. Greenhouse effect vs enhanced greenhouse effect.
Worked example: If producers contain 20,000 kJ m-2 yr-1 and transfer efficiency is 10%, primary consumers receive 2,000 kJ; secondary consumers 200 kJ; tertiary 20 kJ. Reasoning: multiply by 0.10 each step, not subtract 90%; energy is lost at each transfer.
Traps: decomposers are not a trophic level in every food chain; community includes all populations, not just animals; carbon dioxide is not the only greenhouse gas; conservation is not preservation only; pyramids of numbers can be inverted.