Biosphere

BIOSPHERE (from Greek bios-life and sphaira-sphere). The Earth and the layers surrounding it represent a series of concentric shells of a definite average chemical composition. The outer gas shell is called the atmosphere, the following liquid shell is the hydrosphere, and finally the solid one is the lithosphere. The masses of substance constituting them are in a dynamic equilibrium, which depends on pressure and temperature. The area of the entire hydrosphere and parts of the atmosphere and lithosphere, in which organisms live or can live, are conditionally distinguished as a special shell—the B. (Suss, 1875). The upper boundary of the B. occupies up to 9–10 km in the atmosphere, in the hydrosphere it descends to 10 km below sea level, and in the lithosphere its thickness does not exceed 100 m. In places, 'living matter' is collected into huge permanent accumulations, characterizing the face of the earth throughout the course of geological time (tropical forests, taiga, soils with their population, in the sea—bottom and plankton films, coastal accumulations, swamps with their population, etc.). 'Living matter,' which now constitutes the known 500,000 species of animals and 175,000 species of plants, forms in the B. a mass of about 10²¹ g, constituting a layer with a thickness of about 60 km, i.e., 0.1% of the entire earth's crust (Vernadsky). Living beings, accumulating certain chemical elements in their bodies, in the process of vital activity release them outward, noticeably influencing, in this way, the distribution of chemical elements in the B. 'Living matter' is thus a special form of occurrence of chemical elements, and in all the most important physicochemical processes occurring in the earth's crust, it takes a very prominent part. The entire gas regime of the planet, the formation of silt, muds, deposits of fossil coals, oil, silica, limestones, directly depend on the activity of 'living matter' constituting macro- and microorganisms. The direct connection of 'living matter' with the inanimate nature is carried out in the processes of respiration, upon the absorption of oxygen, the release of carbon dioxide and other gases, upon the nutrition with salt solutions, etc. In their totality these processes put into motion huge masses of chemical compounds, and thanks to them and the part of the continuous movement of chemical elements within the B., which is known under the name of 'biogenic migration of elements,' is carried out. Each organism is characterized by a certain dynamic equilibrium of its chemical composition, but, in connection with diverse ecological relations, dynamic-equilibrium systems of a higher order are established between various organisms or groups of organisms, which are the source of the corresponding biogenic migrations. Such relations are observed in cases of parasitism, symbiosis, intraspecific and interspecific struggle for existence, etc. These relations are well illustrated by certain 'food chains' arising from one organism eating another, for example: plants-insects-birds-man, or-algae-fish-mammals. Ultimately, biogenic migration, as well as the entire circulation of matter in general, is supported by the influx of cosmic energy from outside, mainly in the form of solar energy (about 1% of which is absorbed and transformed by green plants), and atomic or radioactive energy of the earth's crust. The organic compounds formed, both in plants and in animals, are stable only within the organism, i.e., in the thermodynamic field of 'living matter,' and are destroyed, releasing the energy contained in them, as soon as they enter the field of the B. Part of them is spent in the processes of nutrition, the other is destroyed after the death of living organisms. Thus, the B. is a place of accumulation of energy released by 'living matter,' not counting the energy contained in the deposits of biogenic origin. BIOTYPE: a) a term introduced (1903) by Johannsen to denote all individuals having the same genotypic composition, i.e., possessing completely identical hereditary predispositions; thus, the concept of the B. coincides with the concept of 'pure line'; in self-pollinating plants the B. will be all individuals obtained from one self-pollinating specimen under the condition of its complete homozygosity; b) the lowest taxonomic unit within the so-called elementary species.