bio23

Biology, 6th Edition

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Greg Steinberg AP Biology Chapter 23 The Evolution of Populations A. Population Genetics a. Darwin and Mendel meet i. Darwin considered his observations to be quantitative, and rested upon the conclusions made by the observations of organisms in a specific population. ii. We now know that quantitative characters are reliant on genetic loci, but early geneticists could only compare obvious “either … or” traits. iii. Population genetics helped provide evidence for Darwin’s theory. 1. Population Genetics emphasizes genetic variation within populations. iv. The genetic variation and natural selection were united during about the 1930’s. v. Modern Synthesis united the theory of evolution with many fields of biology. Among the people who developed this was Dobzhanksy, Wright, Mayr, Simpson, and Stebbins. b. Allele Frequencies i. A population is a localized group of organisms of the same species. ii. A particular species may be spread over a large area, but sections of this area are still populations. Usually islands or such. 1. Members of the same population are more likely to breed with members of the same population, rather than neighboring populations, although breeding may occur. iii. The gene pool of a species is the total sum of the species genes at that given time. iv. For diploid organisms, each gene is represented twice. c. I don’t like the follow stuff i. In a population of x diploid organisms, the total gene copy of a particular gene is 2x. ii. 2x(For Homozygous) + x (For Heterozygous) = y iii. y / 2x = z% d. Hardy-Weinberg i. Hardy-Weinberg theorem explains non-evolving populations. ii. The shuffling of genetic traits has no effect on the gene pool. e. Hardy-Weinberg Equilibrium i. No matter how many times the genes are split up, the results are always the same. You put in what you get. ii. There is always something that alters the results, but if using a large enough population, the variation won’t be noticeable.
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f. Hardy-Weinberg Equation i. (p + q = 1) = (q = 1-p) = (p = 1-q) ii. Homozygous Dominant of offspring = p^2 iii. Homozygous Recessive of offspring = q^2 iv. Heterozygous = 2pq v. p^2 + 2pq + q^2 = 1 vi. This allows us to calculate the frequencies of alleles in a gene pool if we know the frequency of a genotype.
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