Biome

Most biomes are delineated on the basis of their naturally occurring communities of plants, animals, and microorganisms. Exceptions are the so-called anthropogenic biomes, which are strongly influenced by humans and their activities, as in the case of cities and agroecosystems. However, it should be remembered that to some degree, all of Earth's biomes have been influenced by human activities. All organisms, for example, contain trace contaminations of certain organochlorine chemicals of human manufacture, such as DDT and PCBs.

Ecologists have used a number of systems to divide the biosphere into major biomes. A classification of global biomes, modified from one proposed by E.P. Odum, is described below: