March 1, 2021

natural selection

Natural selection conveniently describes how individual traits become more or less common in a population. As such, natural selection is statistical, as we’re primarily interested in the population moreso than individuals within the population.

Two things need to be present for natural selection to take place. First, there must be genetic variation within a population. Second, there must be inheritance of genes between generations.

Random mutations already exist in a population, generating variations. The question, then, is how these random mutations pass into the next generation. Some of these mutations have marginal effect on the organism’s ability to survive and reproduce.; these neutral mutations may pass freely, and randomly, into offspring (see allele flow). Some mutations may help increase reproducibility or survival of offspring. As we’ll see, it’s not always true that deleterious mutations die out and beneficial mutatoins reproduce widely.

Since there are many non-genetic constraints on population survival – eg. food supply, predation, ecological events, disease – as well as non-random reproductive habits, a “selection” of sub-populations occurs. Over a large enough number of generations, these sub-populations can become distinct species. Distinct species are unable to contribute their portion of genetic variations back into the ancestral population (eg., zerbras cannot contribute the genes for stripes back into the horse species).

Content by © Jared Davis 2019-2020

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