Fundamentals of Evolution - Korzh O.P. - 2006

Part I. MICROEVOLUTION

Chapter 4. Mutation Process as an Elementary Evolutionary Factor

4.1. Requirements for Elementary Evolutionary Factors

According to the Hardy-Weinberg principle, an infinitely large panmictic population stabilizes quite rapidly in terms of the quantitative ratios of its existing genes. For an elementary evolutionary event to occur—that is, prolonged and directional Changes in the genotypic composition of a population—certain factors must exert pressure upon it.

As noted previously, an elementary evolutionary phenomenon cannot yet be considered evolution proper, which is a directional process of changes in discrete forms of living organisms. However, it is a necessary prerequisite for any evolutionary changes, which necessitates identifying their underlying causes.

Elementary evolutionary factors must possess specific evolutionary significance, based on which certain requirements can be formulated for them. Triggering microevolutionary mechanisms requires at least Three types of factors that influence the population.

First of all, elementary evolutionary factors must supply the population with novel elementary evolutionary material, without which altering the population's genotypic composition—and consequently realizing an elementary evolutionary event—is entirely impossible. The Introduction/43.html">Action of Certain factors must also cause the original single population to split into two or more new populations, isolated from one another by barriers of any kind. We have already discussed differences in the genotypic composition of various populations; here it should be added that such barriers allow them to embark on independent evolutionary paths of development.

And finally, the action of factors capable of directing the overall evolutionary movement is required. Only in this case can we expect modifications in living organisms, an elevation of their Organization, and the acquisition of new adaptive traits. The combined influence of all the aforementioned types of factors is a mandatory prerequisite for speciation. Today, it is generally accepted to distinguish four elementary evolutionary factors: two of which supply elementary evolutionary material, one creates intrapopulation barriers, and the final one directs the evolutionary process.