The natural community (biocenosis) is the unification of live and inanimate nature which is formed in certain environmental conditions. In these communities each separate organism in a certain way influences all others and also is influenced by their influence. This existence is useful for all community and each separate look. Examples of natural communities - a meadow, the swamp, the steppe, the desert, the ocean.
Each of them is inhabited by the inhabitants. For example, only in the steppe the saiga, a gopher, a feather grass or kipchak meet. It is improbable to see forest animals in the ocean, and sea fishes will not be able to live in the freshwater lake. Each species of animals is adapted to accommodation in a certain natural community. There it finds enough food and a condition for normal activity. Communities are not accidental formations. Living beings and the environment surrounding them conduct constant exchange of substances and energy. They supply each other practically with all necessary for life. Interaction of types provides optimum use of resources of community, limits uncontrolled reproduction of any given organisms. Destroying disabled, sick animals, predators promote improvement of population. Thereby the special living system with own structure, relationship, development and functions is formed. The amounts of substance and energy necessary for living organisms are extremely high. The nutrients absorbed from the environment constantly come back, as a result of activity of organisms. They undergo various transformations, over time breaking up to simpler connections. In such look they can be acquired by plants. That is there is a steady circulation of substances. Each natural community is characterized by a certain set of types. Than the fauna is more favorable and magnificent vegetation of tropics is incomparable with monotonous flora and fauna of the tundra. Such communities are not isolated, they interact with others, forming together the complete systems of higher level of the organization — an ecosystem. All natural ecosystems are connected among themselves and form a live cover of Earth - the biosphere.