4.5 KiB
4.5 KiB
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. Variation: Must be heritable variation. Selective pressures: Environmental conditions that select for certain characteristics against others. Selective advantage: Genetic advantage that improves chance of survival. Fitness: Struggle to survive. Those that survive and reproduce. Examples: - In 1848, 2% black moths as trees were covered in light colored lichen. - 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. Provides new alleles and therefore new sources of variation in a population. Might not immedietly affect phenotype. 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. Can increase genotypic frequencies/homozygous traits. Sexual selection: Selection by mating partners. Artificial selection: Humans selecting favorable traits. 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. 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. Larger effect on small populations. Founder's/Founder effect: A small group leaves the original population, and by change the allele frequency of the group differs. Bottleneck effect: Original population decreases in population size. Survivors represent a small fraction of the alleles that were present before the population decline. |