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Human Biology, Behavior, and Evolution Notes PART 4 [COMPLETE]: 90% on final!

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CAS AN 102
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Phylogenetics and Population Genetics Forces of Evolution: 1.Natural selection: variation, heritability, competition, differential reproductive success 2.Mutation: the ultimate source of variation 3.Gene flow: movement of genes between populations, migration 4.Genetic drift: random changes in gene frequency due to random factors like accidental death Mutation is the ultimate source of variation Gene flow caused by human migration Genetic drift independent of fitness Founder Effect: Intermarriage within a closed community -Founder of Pitcairn Island had blue eyes, has lots of children, and creates new population of blue eyes -Ellisvan creveled Syndrome in Amish (dwarfism, extra fingers) -Genetic bottleneck caused by migration or disease leads to less variation and changes in gene frequency (severely reduces population size and genetic diversity) Sampling variation Genotype frequency Allele frequency 20 BB .4 B = .6 (20x2 + 20 / 50x2) 20 Bb .4 b = .4 10 bb .2 Fixation: when one allele is lost (frequency reaches 1 or 0) Disruptive selection -The average is less fit so selection eliminates the average -Distribution shifts toward each extreme -Favors both homozygotes. Stabilizing/balancing selection -Selection for those in the middle -Eliminates non-average individuals -Favors heterozygote -Average is more fit -Bell-shapes curve. -Highest survival of babies with average birth weight Directional selection -Selection for one homozygote over the others. -Ex: higher hemoglobin concentration in blood for people in higher altitudes in Andes and Tibet Balanced polymorphism -Selection for heterozygotes -Sickle cell anemia and malaria correlation Hardy-Weinberg Equilibrium -Allows us to see if evolution is taking place -If no forces of evolution take place genotype frequencies will remain the same P^2 + 2Pq + q^2 = 1 P + q = 1 Phylogenetics: study of evolutionary relationships among a group of species Cladogram: Diagram of the evolutionary relationships of species Taxa: Group of cladogram Node: Species branch off from main line Monophyletic: The group includes the last common ancestor and all of its descendants Paraphyletic: The group includes the last common ancestor and some but not all of its descendants Polyphyletic: Group contains descendants but not common ancestor Qualitative traits: non-overlapping phenotype variants (hemophilia, ABO blood type, albinism) Quantitative variation: continuous variation, caused by polygenic traits, lot of people in middle and some at either end, bell shaped curve (weight, height, hair color, skin color) Polygenic traits: controlled by multiple genes -Influenced by alleles at two or more loci -Each allele contributes to phenotype Pleiotropy: one gene can have multiple effects (docility linked with white markings on face) Genes & environment (toxins, cultural norms, altitude, temperature, individual experience, nutrition) Modern Synthesis ⁃ From 1920-1950, academics collaborated to explain how transmission genetics fit with Darwin's evolutionary principles ⁃ Ernst Mayr: Biologist, explained speciation ⁃ Ronald Fisher: Statistician, introduced concept of having control ⁃ JBS Haldane: Geneticist, reintroduced Mendlian genetics ⁃ Sewall Wright: Geneticist, relatedness ⁃ Theodosius Dobzhansky: Geneticist, focused on fitness ⁃ George Simposon: Paleontologist, saw past populations as breeding populations ⁃ Established that the production of variation (via mutation) and the shaping of it (via selection) were both necessary to explain adaptation ⁃ Emphasized ma
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