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17.1 Genes and Variation 2. Mendel’s work helped support evolution. 3. Variation is how natural selection happens. 3. Variation comes from mutations. 2. Genotype: combination of alleles (Aa) 2. Phenotype: Genotype + Environment 3. Epigenetics – Environments role 2. Population: group of individuals from a same species. 3. Gene Pool: all genes and alleles in a population 3. Allele frequency: # of times an allele occurs in a gene pool compared to total # of alleles in the pool for the same gene. (shown as a %) 4. Change in allele frequency = evolution Black (B) = 20 (40%) BB = 16% Brown (b) = 30 (60%) Bb = 48% bb = 36% 2. Populations evolve, not individuals 2. Mutations 3. Change in genetic material 3. Most neutral 2. Sexual Reproduction (Genetic Recombination) 3. Independent Assortment 3. Crossing Over 2. Lateral Gene Transfer 3. Can occur between same or different species of single-celled organisms. 3. “pick up genes” 2. single-gene trait = controlled by only one gene 3. only 1-2 phenotypes 2. polygenic traits = traits controlled by 2 or more genes Evolution as Genetic Change in Populations 2. Fitness: passing on alleles. 2. Single-gene allele frequencies change, phenotype changes. black color = absorb more light, heat up faster on colder days, move faster. Why would red be less common? 2. Polygenic traits produce shift in fitness. 3. Directional selection 4. Individuals on end of curve more fit than those in middle or other end 3. Stabilizing Selection 4. Individuals near center of curve more fit. 4. Bell curve narrows. 3. Disruptive Selection 4. Individuals on outer end of curve are most fit. 4. Two distinct phenotypes may form. 2. Series of chance occurrences can cause an allele to become more or less common in a population. 3. Faster if population is small 3. Genetic Drift: random change in allele frequency. 2. Disasters may kill many individuals. 3. Rapid change in allele frequency. 3. Bottleneck Effect: change in allele frequency after reduction in population. 2. Few inhabitants move to a new habitat. 3. Different alleles than main population. 3. Founders Effect: Allele frequency change because of migration of small subgroup. Polydactyly – more common in American Amish 2. Genetic Equilibrium: allele frequencies do not change in a population. 3. No evolution Can sexually reproducing organisms be in genetic equilibrium? Yes. Meiosis and fertilization shuffles. Does not change frequency. 2. Allele frequencies should remain constant unless a factor causes it to change. Frequency of AA + Frequency of Aa + Frequency of aa = 100 2. Five factors that disrupt genetic equilibrium: 3. Nonrandom mating 3. Small Population 3. Immigration or Emigration 3. Mutations 3. Natural Selection *If one or more of these is happening, evolution is happening* The Process of Speciation Turn to page 494 and define these terms. 1. Species 2. Speciation 3. Reproductive Isolation 4. Behavioral isolation 5. Geographic Isolation 6. Temporal isolation Each group must describe one of the events that occurred for the speciation of Darwin’s species. Class will then go around to fill in the rest of the notes. 2. Founders Arrive 3. 3. 2. Geographic Isolation 3. 3. 2. Changes in Gene Pool 3. 3. 2. Behavioral Isolation 3. 3. 2. Competition and Continued Evolution 3. 3.