IV.6 Population genetics often studies the effects of selection on models of a panmictic population with unlimited growth, exposed to hard frequency-independent selection.

Population geneticists were long concerned primarily with the study of natural selection.Consequently, a great many conclusions on the functioning of natural selection were related only to specific situations that are studied by population genetics.

            Real natural populations can have very varied structures and can be the subject of various types of regulation.Population genetics sees evolutionary processes as a shift in the frequency of the various alleles of individual genes in the gene pool.The majority of phenomena in population genetics have been studied genetically on the model of large panmictic, i.e. randomly cross-bred, populations of diploidal organisms that reproduce only sexually under conditions of hard, frequency-independent selection, with unlimited growth.In the individual models, the overall size of the population is mostly considered to be constant; however, the constant nature of this parameter is achieved rather artificially.The frequency of the individual variants is calculated in relative units, obscuring the fact that the relevant population would either have to grow or be artificially reduced to the original size in each generation (Kimura 1978).In real populations, constant population size is ensured by quite different mechanisms, through chemostatic and turbidostatic regulation.The fact that population geneticists mostly completely ignored these ecological aspects of the structure and the behaviour of real populations substantially affected the conclusions that they reached.

            Classical evolutionary models of population genetics can be basically divided into two groups.Models in the first group are concerned with changes in the frequencies of the individual alleles of the individual genes, while models in the second group study changes in the frequencies of the individual phenotypes, the evolution of quantitative traits determined by the simultaneous action of a great many genes.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.