One way to group together areas that share characteristics is to look at the ecosystem of the area. An ecosystem is a group of living organisms interacting with the non-living parts of an environment. Ecosystems can vary in size, eg a single hedgerow or a whole rainforest.
The type of plants and animals found in each ecosystem depends on the type of climate and soils. The harsh conditions of an extreme environment mean that only plants and animal species that have adapted are able to survive in the area. The vegetation, climate and soils are closely linked with one another.
A large ecosystem is called a biome. A biome contains particular plant and animal groups, which are adapted to that particular environment.