what can you tell me about its name?
The term "natural selection" is most often defined to operate on heritable traits, because these directly participate in evolution.
Natural selection
The term "natural selection" is most often defined to operate on heritable traits, because these directly participate in evolution. 
where does all the natural variation necessary for natural selection come from This occurs partly because random mutations arise in the genome of an individual organism, and their offspring can inherit such mutations. what is this all about? Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. were there any theories based on it? Yes, Darwin's theory. how is it classified? It can be classified in several different ways, such as by its effect on a trait, on genetic diversity, by the life cycle stage where it acts, by the unit of selection, or by the resource being competed for.
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Natural selection [SEP] Terminology
The term "natural selection" is most often defined to operate on heritable traits, because these directly participate in evolution. However, natural selection is "blind" in the sense that changes in phenotype can give a reproductive advantage regardless of whether or not the trait is heritable. Following Darwin's primary usage, the term is used to refer both to the evolutionary consequence of blind selection and to its mechanisms. It is sometimes helpful to explicitly distinguish between selection's mechanisms and its effects; when this distinction is important, scientists define "(phenotypic) natural selection" specifically as "those mechanisms that contribute to the selection of individuals that reproduce", without regard to whether the basis of the selection is heritable.