GCSE Biology · Edexcel 1BI0 · Topic 9A
Ecosystems and sampling
Key points
- Levels of organisation: individual → population → community → ecosystem.
- Abiotic factors (non-living): light, temperature, water, pollutants. Biotic factors (living): competition, predation, disease.
- Interdependence: organisms rely on each other for food, shelter and pollination. Parasites live on or in a host and harm it; mutualism benefits both organisms, e.g. oxpeckers and buffalo.
- Core practical: estimate population size with quadrats: mean number per quadrat × (total area ÷ quadrat area).
- Use a belt transect to see how distribution changes with an abiotic factor, e.g. distance from a pond.
- Separate science: only about 10% of energy passes to the next trophic level; efficiency = energy in next level ÷ energy in previous level × 100. Pyramids of biomass show this.
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An ecosystem is the community of organisms in an area together with the non-living parts of their environment. This sub-topic covers how ecosystems are organised, what affects the organisms in them, how to sample populations in the field…
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