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Mechanism of Microevolution.md
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[[Unit 3 (TBD)]]
| Mechanism | Description |
| ----------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Natural Selection | Process where the environment selects individuals in population with certain traits that make them better suited to survive and reproduce.<br>Variation: Must be heritable variation.<br>Selective pressures: Environmental conditions that select for certain characteristics against others.<br>Selective advantage: Genetic advantage that improves chance of survival.<br>Fitness: Struggle to survive. Those that survive and reproduce.<br><br>Examples:<br>- In 1848, 2% black moths as trees were covered in light colored lichen.<br>- In 1898, 95% black moths as the lichen was killed by air pollution resulting from the industrial revolution. |
| Mutation | Mutation are changes to the structure of DNA. Gene mutations are the change in the nucleotide sequence of an allele. Affects genotype frequency.<br>Provides new alleles and therefore new sources of variation in a population.<br>Might not immedietly affect phenotype.<br>If a mutation is harmful it's usually quickly eliminated from the population. |
| Non random mating | Individuals in a population select mates often on the basis of their phenotypes.<br>Can increase genotypic frequencies/homozygous traits.<br>Sexual selection: Selection by mating partners.<br>Artificial selection: Humans selecting favorable traits.<br>Inbreeding: Mating between relatives. |
| Gene flow | Transfer of alleles from one population to another. Individuals can move into or out of a population, which affects allele frequency in a population.<br>Can introduce new alleles to a gene pool of a population. |
| Genetic drift | Refers to changes in allele frequency due to random change alone. The change has nothing to do with their trait.<br>Larger effect on small populations.<br>Founder's/Founder effect: A small group leaves the original population, and by change the allele frequency of the group differs.<br>Bottleneck effect: Original population decreases in population size. Survivors represent a small fraction of the alleles that were present before the population decline. |