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AQA GCSE Biology

Ecosystems and adaptations — AQA GCSE Biology revision

Free revision notes, key terms, common exam traps and 5 practice questions with answers. About 4 minutes to read.

Interdependence

  • Organisms compete for food, water, space, light and mates.
  • Removing one species affects others through the food web.
  • Abiotic factors: light, temperature, water, pH. Biotic: predators, food, disease, competition.

Cycles and biodiversity

  • Carbon cycle: photosynthesis removes CO₂; respiration, decay and combustion return it.
  • High biodiversity makes an ecosystem more stable.
  • Human impacts: deforestation, pollution, land use for building, farming and waste.

Key terms

Abiotic factor
A non-living environmental factor.
Biodiversity
The variety of species in an ecosystem.
Interdependence
Species relying on each other to survive.
Ecosystem
A community of organisms and the physical environment they interact with.
Producer
An organism (usually a plant) that makes its own food by photosynthesis.
Decomposer
An organism that breaks down dead material and waste, recycling nutrients.

Common exam traps

  • Naming a factor without saying how it affects the organism.
  • Confusing biotic and abiotic in data questions.
  • Thinking removing one species from a food web only affects that one species — effects ripple through connected feeding relationships.

Practice questions with answers

  1. 1. Which of these is an abiotic factor?

    • • Predators
    • • Light intensity
    • • Disease
    • • Competition

    Answer: Light intensity

    Abiotic = non-living.

  2. 2. Explain why removing a predator can reduce biodiversity.

    Answer: Prey numbers rise, they over-consume their food source, so other species decline or die out.

    Follow the chain through the food web.

  3. 3. Name two processes that return carbon dioxide to the atmosphere.

    Answer: Respiration and combustion (decay also counts).

    Photosynthesis removes CO₂; these return it.

  4. 4. Which is an example of competition between plants?

    • • Competing for light and water
    • • Sharing pollinators equally
    • • Growing at different times of year
    • • Producing seeds

    Answer: Competing for light and water

    Plants compete for resources needed for growth like light, water, space and nutrients.

  5. 5. Define a 'community' in ecological terms.

    Answer: All the populations of different species living and interacting in a habitat.

    A community is made up of multiple populations of different species.

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