Ecosystems · GCSE Geography

What an ecosystem is

An ecosystem is a community of plants and animals (the biotic parts) and the environment they live in (the abiotic parts, such as climate, soil, water and light).
Producers (plants) make their own food by photosynthesis. Consumers eat other living things: primary consumers eat plants, and secondary consumers eat primary consumers. Decomposers (bacteria and fungi) break down dead material and return nutrients to the soil.
A food chain shows one feeding path. A food web shows how many food chains link together.

Producers: algae, pondweed and reeds. Consumers: tadpoles and water snails (primary), water beetles, frogs and small fish (secondary), and herons (tertiary). Decomposers: bacteria and fungi in the mud.
Nutrient cycling: dead plants and animals sink into the mud, decomposers break them down, and the nutrients are released for plants to take up again.

A change to one part affects the others. If fertiliser runs into a pond, algae grow quickly and block the light. When the algae die, decomposers use up the oxygen, and fish die. This is called eutrophication.
Other changes include draining ponds, introducing new species, removing hedgerows and climate change.

Tropical rainforests are found near the Equator, such as in the Amazon, the Congo and South-East Asia. Hot deserts are found around 30° north and south, such as the Sahara.
Tundra is found at high latitudes, near the Arctic. Temperate deciduous forest grows in the UK and western Europe. Coniferous forest (taiga) covers northern Canada, Scandinavia and Russia. Grasslands include tropical savanna (such as in East Africa) and temperate grasslands (such as the North American prairies).
Where each biome is found depends mainly on climate (temperature and rainfall), which depends on latitude and the global atmospheric circulation.

Ecosystem: A community of living things and the environment they live in.
Biotic: The living parts of an ecosystem, such as plants and animals.
Abiotic: The non-living parts of an ecosystem, such as climate, soil and water.
Producer: A living thing that makes its own food by photosynthesis.
Consumer: A living thing that gets its energy by eating other living things.
Decomposer: A living thing, such as a fungus, that breaks down dead material.
Food web: A diagram showing how many food chains link together.
Nutrient cycling: The movement of nutrients between living things, dead material and the soil.
Biome: A large-scale global ecosystem, such as tropical rainforest.
Eutrophication: Extra nutrients causing algae to grow and then use up the oxygen in water.