How Populations Evolve: Microevolution

1. Mutations
2. Nonrandom mating
3. Natural Selection
4. Genetic Drift
5. Genetic Flow

1. If individuals differ in their survival and reproductive success natural selection will alter their allele frequencies
2. Can only act on existing variation
3. Cannot conjure up new beneficial alleles
4. Acts on the individual level

1. A change in the gene pool of a population due to chance
2. In a small population chance events may lead to the loss of genetic diversity
3. Bottle-neck effect
4. Founder effect

Mechanism of genetic drift that leads to a loss of diversity when a population in greatly reduced

Mechanism of genetic drift that occurs when a few individuals colonize a new habitat
2. The smaller the group the more different the gene pool of the new population will be from the original population
3. E.g. Darwin's finches; Ellis-van Creveld syndrome

1. The movement of individuals or gametes/spores between populations
2. Can alter allele frequencies in a population
3. Spreads advantageous alleles through the species
4. Helps maintain the organisms over a large area as one species
5. Isolation of populations may lead to speciation

1. The contribution it makes to the gene pool of the next and subsequent generations
2. Fittest individuals are those that pass on the most genes to the next generation

1. Direction selection
2. Stabilizing selection
3. Disruptive selection

1. Favors individuals who possess a trait at one extreme of the range of traits
2. When natural selection moves a character towards one of its extreme
3. ex. insecticide resistance in insects and beak size in Darwin's finches

1. Favors individuals who possess an average value for a trait
2. Intermediate forms of a given characteristic are favored over extremes

1. Favors individuals who possess traits at either extreme of a range of traits
2. When natural selection moves a character toward both of its extremes

1. May lead to phenotypic differences between males and females
2. Sexual dimorphism
3. Intrasexual competition
4. Intersexual competition

When males and females in a species show distinctly different appearances

Involves competition for mates usually by males

When individuals of one sex, usually females, are choosy in picking their mates, often selecting flashy or colorful mates