• Species?do not exist by themselves in their own isolated environment; they?interact?with?other species, forming?communities
• A community can be defined as:

Multiple populations of different species living and interacting in the same area

• For example, a garden pond?community?is made up of populations of fish, frogs, newts, pond snails, damselflies and dragonflies and their larvae, pondweed, water lilies, and all other populations living in the pond

• Communities interact with the?non-living components?of the?environment?they live in, forming?ecosystems
• An ecosystem can be defined as:

A community and its interactions with the non-living parts of its environment

• Ecosystems are mostly?self-contained
• There is a?flow of energy?within an ecosystem and the?nutrients?within it are?recycled?(e.g. the carbon, nitrogen and phosphorus cycles)
• There are both?biotic?components and?abiotic?components within an ecosystem
• Ecosystems?vary greatly in size and scale
  • Both a small pond in a back garden and the open ocean could be described as ecosystems
  • A human being could also be described as an ecosystem (there are thousands of species of bacteria living on and in every person)
• Ecosystems?vary in complexity:
  • A desert is a relatively simple ecosystem
  • A tropical rainforest is a very complex ecosystem
• No ecosystem is completely self-contained,?as organisms from one ecosystem are often linked with another ecosystem somehow
  • For example, many birds species are able to migrate long distances to find food sources or breeding locations from multiple ecosystems

Example of an ecosystem

• A forest is an example of a complex ecosystem
• There is a large community of organisms including trees, birds, small and large mammals, insects and fungi
• The?abiotic components?of the ecosystem include the soil type, dead leaves, water from the rain and streams, the rocks, and any other physical or chemical factors
• The abiotic components of the ecosystem?influence?the?community?of organisms (e.g. by providing?habitat,?nutrients and other resources organisms need in order to survive and reproduce)

Levels of organisation in an ecosystem