Chapter 23: The Evolution of Populations

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Chapter 23: The Evolution of Populations. Population Genetics. microevolution change in genetic makeup of a population from generation to generation. macroevolution evolutionary change above the species level. - PowerPoint PPT Presentation

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<ul><li><p>Chapter 23:The Evolution of Populations</p></li><li><p>Population Genetics</p><p>microevolution change in genetic makeup of a population from generation to generation</p></li><li><p> macroevolution evolutionary change above the species level</p></li><li><p> population group of individuals of the same species living in the same area</p></li><li><p> gene pool all the genes in a given population at a given time</p></li><li><p>allele frequency proportion of an allele in a gene pool</p><p>p = dominant alleleq = recessive allele</p><p>f (p) = frequency of the dominant allelef (q) = frequency of the recessive allele</p></li><li><p>Calculating allele frequency:</p></li><li><p>Genotype# of IndividualsGenotypic frequenciesMM1787MM = 1787/6129 = 29%MN3039MN = 3039/6129 = 50%NN1303NN = 1303/6129 = 21%Total6129</p></li><li><p>Hardy-Weinberg Theoremhelps measure changes in allele frequencies over timeprovides an ideal population to use as a basis of comparison</p></li><li><p>Conditions for Hardy-Weinberg Equilibrium:</p><p>Large populationNo gene flowNo mutationsRandom matingNo natural selection hypothetical population that is not evolving rarely met in nature</p></li><li><p>Mutation and sexual recombination only sources of new variations</p><p>mutation changes in nucleotide sequence in DNA</p></li><li><p>point mutations change in one nucleotide</p></li><li><p>gene duplication duplication of a chromosome segment </p></li><li><p>sexual recombination crossing over, shuffling of genes during meiosis</p></li><li><p>Genetic Drift change in allele frequencies due to chanceusually in smaller populationsreduces genetic variation</p></li><li><p>bottleneck effect when a population has been dramatically reduced, and the gene pool is no longer reflective of the original populations</p></li><li><p>Human actions can create a genetic bottleneck</p></li><li><p>founder effect when a small number of individuals colonize a new area; new gene pool not reflective of original population</p></li><li><p>The Fugate family Kentucky's Troublesome Creek</p></li><li><p> gene flow when a population gains or loses alleles</p><p>a movement of fertile individuals leaving/arriving a reduces differences between populations</p></li><li><p> genetic variation heritable variations in a population</p></li><li><p>discrete characteristics are all one discrete variety</p></li><li><p>quantitative characteristics vary along a continuum, usually due to influence of two or more genes</p></li><li><p>average heterozygosity measure of polymorphism in a population</p></li><li><p>geographic variation difference in variation between population subgroups in different areas</p></li><li><p>cline a graded change in a trait along a geographic axis</p></li><li><p> Evolutionary Fitness</p><p> fitness contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals</p><p>(the more offspring that you have that survive = more fit you are)</p></li><li><p>relative fitness fitness of a particular genotype</p></li><li><p>Types of selectiondirectional selection shift toward a favorable variation</p></li><li><p>disruptive selection favors the extremes</p></li><li><p>stabilizing selection favors the mean</p></li><li><p>Heterozygous Advantage when individuals heterozygous Recessive allele is maintained in the population</p></li><li><p>Example: sickle-cell anemia</p><p>prevelence of malaria sickle-cell disease</p></li><li><p>Sexual selection a natural selection for mating success </p></li><li><p>Sexual dimorphism differences between the sexes in secondary sexual characteristics</p></li><li><p>Not necessarily better adaptations; example mane on lion very hot, feathers on peacock very expensive to make</p></li><li><p>Common misconceptions:Natural selection acts on phenotype, not genotype!</p><p>Natural selection does not create more perfect organisms! (what is perfect in one environment may not be perfect in another) </p></li></ul>

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