Microevolution


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microevolution

[¦mī·krō‚ev·ə′lü·shən]
(evolution)
Evolutionary processes resulting from the accumulation of minor changes over a relatively short period of time; evolutionary changes due to gene mutation.
Evolution of species.

Microevolution

 

the aggregate of the actuating evolutionary processes occurring within isolated or neighboring populations of a given species. (Populations here are considered as the elementary evolutionary structure; mutations—the basis for genetic variation—as the elementary evolutionary material; and the mutation process, the waves of life, various forms of isolation, and natural selection, as the elementary evolutionary factors.)

Under the pressure of evolutionary factors, change occurs in the genotypic composition of a population—the leading actuating mechanism of the evolutionary process. The term “micro-evolution,” as counterposed to macroevolution, was once used by certain evolutionists to mean variability and the development of forms within a species. Modern microevolutionary theory developed after the synthesis of genetics and classical Darwinism. The basis for the theory was laid by the Soviet geneticist S. S. Chetverikov in 1926 and the English geneticist R. A. Fisher in 1930. In the modern view (sometimes called the synthetic theory of evolution), all of the basic actuating mechanisms of evolution on all levels occur within species—that is, on the microevolutionary level. Microevolution culminates in species formation—in other words, in the appearance of species that are reproductively isolated from the original and all other closely related species. For this reason, there are no distinctions in principle between microevolution and macroevolution, which differ only in their temporal and spatial scale.

Successful research on the microevolutionary level necessitates the synthesis of populational-genetic experiments and quantitative descriptions of the processes of population dynamics and ecology, study of ethological phenomena, analytical application of the theoretical propositions of genetics, and mathematical models of intrapopulational and interpopulational processes.

REFERENCES

Chetverikov, S. S. “O nekotorykh momentakh evoliutsionnogo protsessa s tochki zreniia sovremennoi genetiki.” Zhurnal eksperimentaVnoi biologii, 1926, vol. 2, issue 1.
Timofeev-Resovskii, N. V. “Mikroevoliutsiia.” Botanicheskii zhurnal, 1958. vol. 43, no. 3.
Shmal’gauzen, I. I. Faktory evoliutsii, 2nd ed. Moscow, 1968.
Mayr, E. Zoologicheskii vid i evoliutsiia. Moscow, 1968. (Translated from English.)
Mayr, E. Printsipy zoologicheskoi sistematiki. Moscow, 1971. (Translated from English.)
Timofeev-Resovskii, N. V., N. N. Vorontsov, and A. V. lablokov. Kratkii ocherk teorii evoliutsii. Moscow, 1969.
Fisher, R. A. The Genetical Theory of Natural Selection. Oxford, 1930.
Huxley, J. Evolution: The Modern Synthesis, 2nd ed. London, 1963.

N. V. TIMOFEEV-RESOVSKII

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In the words of one of its main proponents (Mayr, 1963) the synthetic theory maintains that all evolution is due to the accumulation of small genetic changes guided by natural selection, and that transpecific evolution (macroevolution) is nothing more than an extrapolation and magnification of the events that take place within populations and species (microevolution).
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Such small changes are called "microevolution." The Macroevolution Conference of 1980, however, decided that, contrary to theory, microevolutionary changes did not add up to macroevolutionary changes.