From Big Medical Encyclopedia

HABITAT — a complex of the interconnected abiotic and biotic factors which are out of an organism and defining its life activity. Also volumetric factors of the environment can be abiotic various physical (temperature, humidity, pressure, etc.) (the atmospheres, soils, waters, etc.). Biotic factors of the environment are live organisms (plants, animals, microorganisms), with to-rymi this organism is in various relationship (food, competitive, symbiotic, etc.). Action of biotic factors is shown in the form of interference of the different organisms forming the interconnected links of uniform biocenosis (see).

Relationship in system an organism — the habitat has bilateral character. On the one hand, S. of the lake influences an organism (action), with another — the organism in the course of life activity changes Wednesday (reaction). On the nature of impact on an organism distinguish factors of direct action (the effective environment) and indirect, acting indirectly — through other factors of S. of the lake. Change of one factor of the environment causes change of others that leads to shifts in an ecological situation in general (see. Ecology ). The village of the lake it is dynamic; its changes can be periodic (seasonal, annual, long-term) and neperiodichesklsh. Frequency of changes of S. of the lake causes rhythm of a current of a row fiziol. and ekol. processes (see. Biological rhythms ).

The organism of an animal and the person is S. of the lake of the numerous and various organisms which are in various relationship (see. Symbiosis ). In an organism of the owner they test its direct (Wednesday of the first order) and indirect influence (Wednesday of the second order).

The environment — motive power of processes of speciation: under the influence of factors of the environment there is a selection from initially heterogeneous population of a look (see) the phenotypes adequate to these conditions. As a result the gene pool changes populations (see) that at preservation of these conditions of the environment, stability of population shifts in time and restriction of a panmixia causes divergence and leads to formation of a new look. On the other hand, S. of the lake, being one of factors of action of natural selection, can cause convergence — ecological and morfol. similarity of organisms of various systematic situation (see. Natural selection ).

For the person S. of the lake practically all is environment (see). Therefore these or those factors of the environment under certain conditions can serve as an origin various fiziol. reactions in an organism — from adaptation (see. Adaptation , Adaptation ) before development patol. states (see. Pathogeny , Aetiology ).

Live organisms not only adapt to S. of the lake, but also actively change it; therefore distinguish primary and secondary (transformed) habitats. In sovr. to the biosphere the huge role is played by processes of anthropogenous transformation of the environment. Activity of the person has global character, in terms of the scope of and to effects is comparable to geological processes. On this basis V. I. Vernadsky formulated ideas of a special cover of Earth — the noosphere connected directly with activity of the person.

See also Environmental control .

Bibliography: Kashkarov D. N. Wednesday and community (Bases of a synecology), M., 1933; Novikov G. A. Fundamentals of the general ecology and nature protection, JI., 1979; Odum Yu. Fundamentals of ecology, the lane with English, M., 1975; Sketches on stories of ecology, under the editorship of G. A. Novikov, etc., M., 1970; Pavlovsky E. N. Organizm as habitat, Nature, No. 1, page 80, 1934; Elton Ch. Zooecology, the lane with English, M. — JI., 1934.

V. Yu. Litvin.