What natural factors isolate some populations of organisms from other populations of the same species?

Isolation (from French isolation – separation, separation) of a population from other populations of its species also serves as an elementary factor in evolution, since it complicates or precludes the free crossing of its individuals with individuals of other populations of the same species.
Usually isolation leads to the separation of intraspecific groups and the formation of new species.
Isolation does not create genetic changes in the population, but it reinforces and enhances genotypic diversity.
Isolation of a population from other populations of a species in nature can occur in various ways. Often this is served by insurmountable territorial-mechanical or geographical barriers (river, lake, mountain range, freeway, man-made landscape, etc.).
Populations of sedentary organisms can be isolated from each other with just a few meters of space.
Isolation can occur in the case of biological (reproductive) non-crossbreeding of individuals due to either behavioral differences or environmental characteristics (preference for different habitats, seasonal and temporary mismatches of breeding periods), morphophysiological (differences in the sizes and structures of organisms and individual organs), as well as genetic differences ( incompatibility of germ cells), etc. All these forms of isolation arise independently of each other and can manifest themselves in various combinations.
Prolonged isolation of a population can lead to the independence of its gene pool from the gene pool of other populations of the species, as a result of which the isolated population can become an independent new species.

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