An ecosystem is a natural system consisting of all plants, animals and microorganisms (biotic factors) in an area functioning together with all the non-living physical (abiotic) factors of the environment.

Central to the ecosystem concept is the idea that living organisms are continually engaged in a set of relationships with every other element constituting the environment in which they exist.

A terrarium is another place where several populations will peacefully co-exist in the same habitat. Vivaria are habitats where several plant and animal populations live together. Within any shared habitat, behavior influences the survival of a species. Behavior can be instinctual or learned.

Biomes are ecosystems where several habitats intersect. The Earth itself is one large biome. Smaller biomes include desert, tundra, grasslands, and rainforest.