Ecology is a core part of GCSE Biology. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Carbon cycleMovement of carbon via photosynthesis, respiration, decay
Nitrogen cycleSoil bacteria recycle nitrogen for plants and animals
EutrophicationFertiliser runoff causes algal blooms that kill fish
DeforestationRemoving forests, releasing CO2 and cutting biodiversity
Climate changeLong-term warming from greenhouse gases like CO2
ConservationProtecting species and habitats from human harm
Trophic levelA feeding stage in a food chain
Energy transferOnly about 10% of energy moves up each level
BiomassThe mass of living material at a trophic level
QuadratA square frame used to sample organisms in an area
Capture-recaptureMethod to estimate animal population sizes
Sample meanAverage count per quadrat, used to scale up
EcosystemAll organisms in an area plus their non-living environment
PopulationAll organisms of the same species in one area
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
How do decomposers return carbon to the atmosphere?✗ Decomposers release carbon by physically breaking matter into smaller pieces. ✓ They respire — breaking down dead organic matter and releasing CO2.
Why are food chains usually limited to about 4 or 5 trophic levels?✗ There aren't enough types of animals to fill more trophic levels. ✓ Only ~10 percent of energy is transferred between trophic levels; eventually too little energy remains to support another level.
Why is interspecific competition between similar species important?✗ Competition only happens between predators and their prey. ✓ Two species cannot occupy exactly the same niche indefinitely — competition often leads to displacement or niche divergence.
In quadrat sampling, why are quadrats placed randomly?✗ To save time ✓ To avoid bias in the sample
Is energy created as it passes up a food chain?✗ Energy is created at each trophic level, so top predators have the most. ✓ No — energy is transferred and much is lost (mainly as heat) at each level, so only about 10% passes on.
Practise Ecology — free games
Test yourself with these quick revision games for this topic:
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