ARTIFICIAL SELECTION

From Big Medical Encyclopedia

ARTIFICIAL SELECTION — the choice on desirable signs of animals, plants or microorganisms for their further cultivation. The term «artificial selection» is introduced by Ch. Darwin who divided this form of selection into two look for the first time - unconscious (spontaneous) and methodical (purposeful). The deputy found broad application in medical and laboratory practice, in particular at removal of new grades of medicinal plants, pure lines of laboratory animals, in a gnotobiologiya etc.

the Deputy was applied by the person in an extreme antiquity and consisted in cultivation perhaps of the best individuals among the cultivated animal and tame plants (the unconscious Deputy). From this form of selection there is a modern mass Deputy going on external signs (phenotype) of an organism. At the same time efficiency of the Deputy depends on degree of heritability of signs. E.g., the size of a yield of milk at cows is characterized by small heritability and therefore the most intensive selection on this sign cannot significantly influence the size of a yield of milk of descendants of this individual. On the other hand, a zhirnomolochnost — the sign which is characterized by high hereditary conditionality and selection on this sign is rather effective. The methodical selection which is carried out much quicker is based on individual assessment of posterity of a separate individual that gives the chance to estimate to some extent genetic features of parent forms (see. Genotype ). A basis for action of the Deputy is hereditary heterogeneity on this sign or property of the individuals making breed or a grade. There are special methods of increase in this hereditary heterogeneity which in the general form are coming down to different forms hybridizations (see) and artificial calling of mutations usually radiation or chemical mutagens (see. Mutation ). In posterity of this or that sign apply closely related crossing and cultivation to fixing (inbreeding in livestock production, inbreeding in crop production). To prevent degeneration of posterity as a result of the closely related crossing which is characterized by the lowered viability in economy apply interpedigree and interstrain crossing (outbreeding). Inbreeding, outbreeding and selection as methods of selection mutually supplement each other and give the chance of removal of modern highly productive plant varieties and breeds of animals. A special case of the Deputy is the linear selection characteristic of populations of plants self-pollinators, and the clonal selection taking place at the organisms capable to asexual reproduction (it is widely applied in mikrobiol, the industries).

Studying of practice of crop production and livestock production on use of the principles of the Deputy helped Ch. Darwin to open patterns natural selection (see) as main motive power of evolutionary process (see. Darwinism , Theory of evolution ). Despite external similarity between processes of the Deputy and natural selection, they are essentially various: The deputy always has a definite purpose, i.e. is aimed at the development in posterity only of separate qualities, valuable to economy (actually selection); natural selection is connected with maintenance of the general high viability of this population and by the nature is statistichny. By means of the methodical Deputy almost all modern grades of cultivated plants and domestic animals are removed. It is necessary to emphasize that the methods of evidence-based selection developed for vegetable and animal organisms cannot be transferred to human society as it sometimes became (see. Racism ).


Bibliography: Darwin H. Compositions, the lane with English, t. 3, M. — L., 1939; Lerner I. M. and Donald X. P. Modern achievements in animal husbandry, the lane with English, M., 1970; Lobashov M. E. Genetics, M., 1970, bibliogr.; Shmalgauzen I. I. Problems of Darwinism, L., 1969, bibliogr.

A. V. Yablokov.

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