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Evolutionary Forces (Mutation•ultimate source of new variation in…
Evolutionary Forces
Mutation, Gene Flow, Genetic Drift, Natural Selection, and Interaction of Forces
Mutation•ultimate source of new variation in DNA•change in the genetic code•random•new combinations of nucleotide bases (point; frameshift)
For evolutionary importance,the mutation must occur in the DNA in a gamete.
example of a mutation leading to more complex brains:primates have complex, folded brains, including humans (most extreme)•other mammals, e.g., mice, do not have the folds / complexity•insertion of human brain gene (ARHGP11B) into mouse brain
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It is the result of a single nucleotide base mutation (C to G) that caused a frameshift in how ARHGP11A was read by mRNA
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Gene flow is one reason why humans today are all one species.•humans tend to be highly mobile•migration to other areas increases gene flow between populations•majority of genes flowing into a population are from nearby areas
Genetic Drift: Random factors cause allele frequencies to either increase or decrease over time in a population.
If no other evolutionary processes are operating & there is enough time, eventually an allele will become fixed at either 0.0 (absent) or 1.0 (100%).
Given enough time, genetic drift reduces variation in a population.
Bottleneck Effect: a type of sampling error•in a relatively small population, if some individuals are removed by random chance, then the genetic material they carry also is removed from the gene pool
Founder Effect: a type of sampling error•a group of people move to another place, such as an island•they carry only a partial representation of the genetic variation in the gene pool of the population from which they came
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Interaction of Forces - Evolutionary forces can be acting at the same time in populations, with mutations providing new variation
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