Fundamentals of Environment and Ecology
Scope and definitions
The exam checks whether you can define environment and ecology precisely, place organisms at the correct level of organisation, and apply habitat/niche and energy-flow rules in short explanations and calculations.
Core concepts
- Environment = all biotic and abiotic conditions surrounding an organism; ecology = the study of interactions between organisms and their environment.
- Levels of organisation: organism → population → community → ecosystem → biome → biosphere.
- Habitat is the address; niche is the profession (role plus resource use). Two species may share a habitat but not an identical niche without competition.
- Ecological factors: climatic (light, temperature, rainfall), edaphic (soil), topographic and biotic.
- Energy flow is unidirectional; the 10% law states that roughly 10% of energy passes to the next trophic level.
Worked example
A grassland has 20,000 kJ m⁻² yr⁻¹ at the producer level. If 10% passes to each successive level, energy at the secondary consumer (third trophic level) is 20,000 × 0.1 × 0.1 = 200 kJ m⁻² yr⁻¹. The tertiary consumer receives 20 kJ. The loss occurs at each transfer as respiration, heat and undigested matter, so food chains rarely exceed four or five links.
Traps
- Mixing habitat with niche.
- Confusing gross primary productivity (total fixed) with net primary productivity (GPP minus respiration).
- Treating the 10% law as exact rather than a rough ecological generalisation.
- Saying energy cycles; matter cycles, but energy flows.