How can artificial selection change a species
Selection (Latin selectio = choice) consists in a broad sense of three forms:
Natural selection: Living beings that are better adapted to their environment increase the likelihood of their genes being passed on than living beings that are less adapted (see explanation below).
Sexual selection: Internal selection of sexual partners resulting from the competition for reproductive partners. Sexual selection also explains numerous phenotypic characteristics that would actually be disadvantageous in terms of natural selection (e.g. the plumage of the peacock. This hinders the escape from predators, but is an important "courtship tool")
Artificial selection: Man-controlled selection to promote certain characteristics in animal and plant species (e.g. higher milk yield from cows, crop plants resistant to diseases such as wheat or small animal breeding)
The basic assumption of natural selection is the fact that individuals who live longer can pass on their genes more often. The better an organism is adapted to its natural environment, the more often it will be able to pass on its genes to the next generation. One also speaks of the term fitness.
Charles Darwin recognized this mechanism and spoke of the "survival of the fittest" in his work "On the Origin of Species". This phrase is often misunderstood and translated as "survival of the fittest". Darwin means the survival of the best adapted individual. It is not the strongest who bring their genes into the next generation, but those who are best adapted to the external environment. This inevitably leads to a longer lifespan and thus to more offspring (ideally). It does happen that even less well-adapted individuals reproduce and thus pass on their genes to the daughter generation. For this reason too, selection is a statistical probability process. Because an optimal adaptation to a habitat does not guarantee successful reproduction by a long way. Countless processes of an extra-specie and intraspecific nature play a role. That is why one has to look at the populations more as a whole when selecting them. Although less well adapted individuals also bring their genes into the gene pool of the next generation, statistically speaking, however, less often than those who are better adapted. In this way, favorable alleles become more common in the gene pool, while disadvantageous alleles become rarer.
At this point the concept of selection pressure should be briefly explained: Selection factors (see here abiotic selection factors; biotic selection factors) act on all living beings, which "press" on all populations and thus determine the direction of evolution. This does not happen in an active process, but passively. Populations are adapted to the surroundings through selection and do not adapt themselves.
The three selection types are presented below:
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