degeneration in biology

From Big Medical Encyclopedia

DEGENERATION in biology (Latin degenerare to degenerate) — process of simplification, involution.

Degeneration the general — simplification of the organization (according to A. N. Severtsov) — one of the directions of evolutionary process, implementation to-rogo along with increase in the organization (aromorphosis) and private changes (idioadaptation) provides biol, progress, i.e. increase in fitness in the course of evolution (see. Theory of evolution ). The degenerating animal species are, e.g., tunicates, tape-worms, usonogy crayfish at whom one systems of bodies (a reproductive system, protective bodies, etc.) develop towards progress, and others (a chord, muscular system, bodies of active food, etc.) — are in a condition of a partial or full reduction. Can be the general D.'s reasons transition from a mobile way of life to sedentary, adaptation to parasitic existence in an organism of the owner. At the same time studying of ecology of the sedentary (motionless) and parasitizing organisms shows that these animals, despite D.'s phenomenon in separate systems, develop on the way biol, progress — are presented by a large number of childbirth, types and versions, have a wide area of distribution etc.

Degeneration private — a reduction of the bodies which are normally developed at ancestors, but lost the functional value at descendants (e.g., loss of extremities at snakes, a rudimentation of muscles of an ear at the person, etc.). Private D. is followed by progressive changes of other systems and bodies; differs from the general D. in the fact that the structure of an organism as a whole does not become simpler.

Degeneration in morphology — process of an atrophy and destruction of separate cells or bodies in the course of their ontogenesis (e.g., disappearance of a tail at tadpoles at its transformation into a frog).

Degeneration in pathology. The term is entered by R. Virkhov allowing a possibility of «regeneration» of cells. This concept remained in cytology for designation of process of adjournment in cells of various substances causing loss by a cell of ability to normal functioning and division. These substances can be an endogenous origin and collect as a result of any patol, influence or an exogenous origin, being result of penetration into a cell of substances from the outside. The abnormal substances which are deposited in a cell happen various by the nature: lipids (fatty D.), pigments (pigmental D.), etc. (see. Cell ).

Bibliography: Palikar And. and Besse M. Elements of pathology of a cell, the lane with fr., M., 1970; Severtsov A. N. Main directions of evolutionary process, M., 1967, bibliogr.

T. A. Zaletayeva.