Biological evolution

# Biological evolution - Chapter 3 Evolutionary Forces...

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Chapter 3: Evolutionary Forces Biological evolution = genetic change over time Microevolution = changes in frequency of alleles from one generation to next Breeding population = a group of organisms that tend to choose mates within the group. *Problems: Percentage of people married to each other in town varies / subjective as to how to define a true “breeding population” Determining difference between total census population / breeding population After population is defined, determine genotype/allele frequencies Genotype frequency: Measure of relative proportions of different genotypes within population Number of people w/ each genotype ___________________________________________ = Frequency Total Number of People E.G. 18 people with genotype NN in population of 200 18/200 = . 009 = frequency Frequencies = proportions Total frequency of all genotypes add up to 1 Allele frequency: Measure of relative proportions of different alleles within population. Number of each allele _____________________________ = Allele frequency Total number of alleles E.G. In Example, total number of alleles is 400 b/c each person has 2 alleles. Number of alleles for each genotype (x) number of people within genotype = Number of M alleles for each genotype E.G. 2 (x) 98 = 196 M Alleles, etc. for all frequencies. Then divide total number by 400. All alleles also add up to 1 If man with genotype MN mates with woman with genotype MN 25% offspring = MM, 50% = MN, 25% = NN Hardy –Weinberg equilibrium = relates allele frequencies in population to expected genotypes in next generation

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