This area is a relatively thin layer of seas, lakes, streams, land to soil depth of a few meters, and atmosphere to an altitude of a few kilometers.
Solar energy drives nearly all ecosystems.
Availability of light can determine habitat. Animal and plant behavior is often sensitive to photoperiods. Physical structure, pH, and mineral composition of soil limit distribution of plants and hence animals that feed on them. May be patchy, with several communities represented in one biome. Prevailing climate, particular temperature and rainfall, is most important factor in determining what kind of biome develops.