Ecosystems, Habitats and Communities — AQA GCSE Biology
Ecology studies how organisms interact with each other and their environment. This topic introduces the key levels and competition.
Key terms
- Habitat — the place where an organism lives.
- Population — all the organisms of one species in a habitat.
- Community — all the populations of different species in a habitat.
- Ecosystem — the interaction of a community with the non-living (abiotic) parts of its environment.
Competition
To survive and reproduce, organisms need a supply of materials from their surroundings and from other organisms. They compete for these resources:
- Plants compete for light, space, water and mineral ions from the soil.
- Animals compete for food, mates and territory.
Interdependence and stable communities
Within a community, species depend on each other for food, shelter, pollination and seed dispersal — this is interdependence. If one species is removed, it can affect the whole community.
A stable community is one where all the species and environmental factors are in balance, so the population sizes remain roughly constant over time.
Exam tips
- Learn the definitions: habitat, population, community, ecosystem.
- Know what plants and animals each compete for.
- Define interdependence and a stable community.
- A stable community has roughly constant population sizes.