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Evolutionary processes include natural selection

Evolutionary processes include natural selection - Personal...

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Personal Essay Response Evolution is the convergence of independent and random events that somehow result in the diversity if life that we see, each life form being suited to its unique environment. Natural selection and genetic drift, in combination with isolation of gene flow, can help to explain the diversity of species. Natural selection and genetic drift result in changes in allelic frequencies over time. They act on heritable variation in a population, which is introduced through mutation (Freeman, 2005). Through natural selection, differential reproductive success is based on heritable variation (Freeman, 2005). The traits that contribute to high reproductive success therefore increase in frequency in a population over time. Through genetic drift, the simple “chance” of random sampling can change the allelic frequencies in a population (Campbell, 1993). However, in order to result in diversity, the processes of natural selection and genetic drift must be combined with isolation of gene flow between two populations. Through gene flow, alleles can move between populations, decreasing differentiation among populations (Su et al., 2003). Therefore, speciation and diversity results when populations of the same species become genetically isolated by lack of gene flow. Then, genetic divergence can occur as natural selection, genetic drift, and mutation are allowed to proceed independently in the populations. Populations can become genetically isolated from each other if they occupy different geographic areas (allopatric speciation, Campbell, 1993), if they use different habitats within the same area (sympatric speciation, University of California, 2008), or if one population is polyploidy and cannot breed with the other (University of California, 2008). One example of evolution leading to speciation and diversity is the Galapagos Finches. As a result of a monsoon, an ancestral population split into separate populations occupying different islands (Alters, 2006). This resulted in isolation and a lack of gene flow. Then, mutation, natural selection, and genetic drift acted independently on the two populations. The descendent populations evolved in different environments, acquiring different characteristics through the selection of certain alleles. In one case, the availability of large seeds on the island conferred a reproductive advantage to finches with larger, deeper beaks (Alters, 2006). In 12 years, the average bill size in the new population of finches was much
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