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Biology Chapter 16
Final Review
| Question | Answer |
|---|---|
| Two important factors Darwin was unable to explain w/o understanding of heredity | He did not know the source of variation central to his theory. He could not explain how traits were passed from one generation to the next. |
| Population | a collection of individuals of the same species in a given area |
| Gene pool | the combined genetic information of all members of a particular population. contains more than one allele for each inheritable trait. |
| Sources of genetic variation | mutations, gene shuffling |
| Mutation | any change in a sequence of DNA. They can be limited to a single DNA base, affect lengthy segments of a chromosome, affect an organism's phenotype and fitness. |
| Why do mutations occur? | Because of mistakes in the replication of DNA or from radiation or chemicals in the environment. |
| Gene shuffling | creates most inheritable difference. Due to chromosomes moving independently and crossing over. |
| Sexual reproduction | major source of variation, can produce many different phenotypes, can produce many different genetic combinations. However, it cannot change the relative frequency of alleles in populations - it just shuffles them up. |
| # of phenotypes for a trait depends on | how many genes control the trait. |
| Most traits are controlled by | multiple genes |
| Natural selection on single gene traits | can change allele frequencies |
| If a trait made an organism less likely to survive, it might... | disappear from the gene pool. |
| If a trait had no effect on an organism's fitness, then... | it would not be under pressure from natural selection, so its frequency would remain unchanged. |
| Natural selection can affect the distributions of phenotypes 3 ways | directional selection, stabilizing selection, disruptive selection |
| Directional selection | individuals at one end have higher fitness than those in the middle or the other end. graph shifts |
| Stabilizing selection | Individuals near the center of the curve have higher fintness than individuals at either end. Gets skinnier. |
| Disruptive selection | individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle. Graph bends or splits in middle. |
| Genetic drift | random change in allele frequencies in small populations |
| Founder effect | situation in which allele frequencies change as a result of the migration of a small subgroup of a population |
| Hardy-Weinberg principle | Allele frequencies in populations will stay the same unless something makes them change. |
| Genetic equilibrium | situation in which allele frequencies remain constant |
| 5 conditions reuired to maintain genetic equilibrium | random mating, large population, no movement in/out, no mutations, no natural selection |
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