Definition · Plain-language
Ecosystem
An ecosystem is a community of living organisms together with the non-living parts of their environment, all interacting as a system.
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Living and non-living parts together
An ecosystem is made of two kinds of components working together. The living, or biotic, parts are all the organisms — plants, animals, fungi and microbes. The non-living, or abiotic, parts are the physical surroundings: water, air, soil, sunlight, temperature and minerals. What makes it an ecosystem rather than just a list of things is that these parts interact. Plants need light and water; animals need plants and oxygen; and the organisms in turn affect the soil, air and water around them. The whole forms a single working system.
Communities, habitats and populations
Within an ecosystem, biologists use a few linked terms. A habitat is the place where an organism lives. A population is all the members of one species in an area. A community is all the different populations living and interacting in the same place. The ecosystem is the community plus its non-living environment. So the terms nest together: individuals make up populations, populations make up a community, and the community together with its physical surroundings makes up the ecosystem.
How ecosystems work
Two things flow through an ecosystem: energy and nutrients. Energy enters as sunlight, is captured by plants in photosynthesis, and passes along food chains and food webs from one organism to the next, with much lost at each step. Nutrients, such as carbon and nitrogen, are recycled: decomposers break down dead matter and return them to the soil for plants to reuse. A healthy ecosystem stays roughly in balance, but it can be disturbed — by the loss of a species, pollution or climate change — which can ripple through the whole system.
Key facts
At a glance
- Definition: living organisms plus their non-living environment, interacting
- Biotic parts: the living things — plants, animals, fungi, microbes
- Abiotic parts: the non-living surroundings — water, air, soil, light, temperature
- Community: all the populations living and interacting in an area
- Energy: flows in from sunlight, along food chains
- Nutrients: are recycled by decomposers
Common misconceptions
What people often get wrong
Often heard: An ecosystem is only the living animals and plants in an area.
Actually: An ecosystem includes both the living organisms and the non-living environment — water, air, soil, light and temperature. The non-living parts are essential, because the living things depend on and interact with them.
Often heard: Ecosystems are always very large, like a forest or ocean.
Actually: Ecosystems come in all sizes. A single pond, a rotting log or even a puddle can be an ecosystem, as long as living organisms interact with their non-living surroundings. Size is not what makes something an ecosystem.
Often heard: The parts of an ecosystem do not really affect each other.
Actually: The parts are closely linked and interdependent. A change to one part — losing a species, adding a pollutant — can ripple through the whole system. This interaction is exactly what makes it an ecosystem rather than a collection of separate things.
Going deeper
