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Bio ch 23
| Question | Answer |
|---|---|
| natural selection acts on what? evolution acts on what? | natural selection acts on individuals (phenotypes) evolution act on populations (allele frequencies) |
| what's microevolution | change in allele frequencies in a population over generations |
| what's macroevolution | broad evolutionary patterns above the species level (speciation, extinction) |
| 3 main mechanisms of microevolution. which one increases adaptation | natural selection, genetic drift, gene flow natural selection increases adaptation |
| what happens if there's no genetic variation | evolution cannot occur, no raw material for change |
| what's a cline | gradual change in a trait across a variable (geographic gradient) |
| how do mutations affect variation | creates new alleles, increasing genetic diversity |
| how does sexual reproduction increase variation | crossing over, independent assortment, random fertilization |
| how does rapid reproduction increase genetic variation | more generations in less time causes more mutations to accumulate = faster evolution |
| what's the hardy Weinberg prinicple | no evolution= allele frequencies stay constant |
| 5 conditions for hardy-weinberg equilibrium. what happens if one condition is violates | no mutations random mating no natural selection large population no gene flow if one is violated evolution occurs |
| what's natural selection | differential success in survival and reproduction can cause adaptive change where certain alleles are passed to the next generation |
| genetic drift/ when is it strongest | random change in allele frequencies (due to chance events) founder/bottleneck effects strongest in small populations |
| founder effect | a new population started by a few individuals causes low variation |
| bottleneck effect | sudden reduction in population size causes loss in variation |
| gene flow | movement of alleles between populations |
| what differential selection | favors one extreme |
| what's stabilizing selections | favors intermediate traits |
| disruptive selection | favors both extremes |
| what's relative fitness | contribution an individual makes to the gene pool compared to others |
| whats sexual selection | selection for mating success |
| whats sexual dimorphism | differences in characteristics between males and females |
| intrasexual selection | competition within the same sex (male vs male) |
| intersexual success | mate choice (usually female chooses) |
| how does diploidy preserve variation | by allowing individuals to carry 2 diff alleles for each genes, it hides recessive alleles from natural selection |
| what's balancing selection | maintains multiple alleles, allows multiple phenotypes to be advantageous in an environment |
| heterozygote advantage | heterozygotes have higher fitness than both homozygotes |
| why can't natural selection create perfect organisms | works on traits that already exist historical constraints (structures from ancestors come even if not ideal) trade offs (a trait may be beneficial in one way but harmful in another way) random events (what's perfect today isn't tomorrow) |
| which mechanism leads to adaptation in an population | natural selection, increases beneficial traits |
| how can gene flow increase fitness in a population | it introduces new alleles which causes an increase in genetic variation which can improve survival and reproduction |
Created by:
Lilyhowes