natrual selection and genetic variation
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Natural selection cannot work without genetic variation. Variation is introduced at the molecular level through mutation, it takes shape at the cellular level through meiosis and fertilization, and it is expressed at the individual level through protein synthesis. However, which genotypes and phenotypes confer high fitness will depend upon the environment and it's specific selective pressures.
Charles Darwin discovered the theory of natural selection, after years of research and observation. Natural selection is defined as "The mechanism of evolutionary change; referring to genetic change, or changes in the frequencies of certain traits in populations due to differential reproductive success between individuals"(Jurmain et al. 401). Darwin realized that selection was key to evolution, that in the struggle for existence those individuals with favorable variations would survive and reproduce, and those with unfavorable variations would not. There are three main parameters for natural selection: A trait must be inherited to have importance in natural selection. Selection can only work where variations previously existed. And finally, fitness will change as the environment changes...