vault backup: 2026-11-13 14:33:23

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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.                                                                                                                                                                                     |
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+[[Unit 3 (TBD)]]
+Natural selection is situational. It requires heritable variation, competition, and selective pressures.
+==Selective pressure== are environmental conditions pressuring traits.
+==Selective advantage== is a genetic advantage.
+
+Sexual selection is mate selection for a particular phenotype. It may affect fitness.
+Females choose their mates.
+Good genes hypothesis: Females choose mates on traits that improve chance of survival.
+Runaway hypothesis: Females choose on basis of traits that improve male appearance.
+Sexual dimorphism: Different characteristics between male and females to the point that they appear to be separate species.
+Intersexual selection: Females choose mates based on appearance/phenotype/behavior.
+Intrasexual selection: Competition between the same sex of same species to pass on DNA.
+
+Stabilizing selection: The intermediate phenotype is favored.
+Directional selection: Favors phenotypes at an extreme of the range, resulting in the curve being shifted towards that extreme.
+Disruptive selection: Both extremes are favored at the same time. Can eliminate the intermediate phenotype, resulting in speciation.
+![[Pasted image 20261113110619.png]]