21_MicroevolutionFinal

21_MicroevolutionFinal - Microevolution The X-Men are...

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The X-Men are fictional products of microevolution. Mutation is just one of the forces of microevolution. Microevolution
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Microevolution Click here to go back to LOM Evolution via natural selection results from a population of individuals interacting with their environment. Individuals best adapted to the environment are more likely to survive and reproduce and pass on the genetic traits that allowed them to be successful to the next generation. Passing on traits means that mating is required since that is how the next generation is produced. Because of the requirement for reproduction, evolution takes place at the level of populations, not species or individuals. The definition of an individual is self-explanatory while a population is a group of individuals that are likely to interbreed due to living in close proximity to one another. A species can then be thought of as a collection of populations. Using humans as an example, you are an individual, the people of San Diego represent a population, and the human species consists of all the humans in the world. Humans living in San Diego are more likely to mate with one another than with humans living in say, Istanbul, and thus they represent a population. Populations are the functional unit of evolution because reproduction is required to pass along genes to future generations. In the previous e-module, evolution was described as descent with modification. Passing on favorable traits means passing on favorable genes or more specifically favorable versions of each gene called alleles . Every individual in a population has the same genes in their genome but each individual has different alleles. Remember that each individual has
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Click here to go back to LOM Click here to go back to LOM two alleles of every gene (one contributed by the mother and one contributed by the father). The particular alleles that an individual has varies within a population which creates variety in the genotypes and thus in the phenotypes of a population. Evolution of a population leads to changes in allele frequencies in a population's gene pool from generation to generation. This is called microevolution . A gene pool is all the alleles of all the genes found in a population while allele frequency refers to how common a particular allele is in a population's gene pool. Scientists calculate allele frequencies to determine how populations are evolving over time. To determine allele frequency, divide the number of times an allele of interest appears in the gene pool by the total number of alleles for that gene in the gene pool. Let's consider the gene zee, which has two alleles, Z and z. We find there are 60 Z alleles and 40 z alleles present in our population of 50 individuals. What is the allele frequency of Z? There are 60 Z alleles and 100 total alleles (60 + 40) so the allele frequency of Z is 60/100 or 0.60. Since the total frequency of all the alleles in a population's gene pool must be 1, we can calculate the frequency of the other allele, z, by
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This note was uploaded on 04/21/2008 for the course BIOL 100 taught by Professor Lee during the Winter '07 term at San Diego State.

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21_MicroevolutionFinal - Microevolution The X-Men are...

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