Ecosystems and interdependence · Year 13
An ecosystem is all the living things in an area together with their non-living surroundings: a pond, a wood, a coral reef. The organisms depend on each other for food, shelter and pollination, and they compete for what they need. Living and non-living factors decide which organisms can survive there and how many.
Key facts
- An organism lives in a habitat. A population is all the organisms of one species in a habitat. A community is all the populations living there. An ecosystem is the community and the non-living (abiotic) parts of its environment.
- Abiotic factors are non-living: light, temperature, water, soil pH and minerals, wind, carbon dioxide and oxygen levels.
- Biotic factors are living: the food available, predators, new diseases (pathogens), and competition from other species.
- Plants compete for light, water, space and mineral ions from the soil. Animals compete for food, mates, water and territory.
- Interdependence: in a community, each species depends on others for food, shelter, pollination and seed dispersal. A change in one population affects the others.
- Predator and prey numbers rise and fall in cycles. When prey increase, predators have more food and increase too, a little later; then prey decrease, and later so do predators.
- A stable community keeps roughly the same species and numbers over time, because its biotic and abiotic factors stay in balance (for example a tropical rainforest).