Lecture 20: Microevolution continued

Five Agents of Evolutionary Change

•Mutation

–Mutation rates are generally low

–Ultimate source of genetic variation.

•Gene Flow

–Movement of alleles from one population to another.

Five Agents of Evolutionary Change

•Non-Random Mating

–Inbreeding

•Genetic Drift

–Frequencies of particular alleles may change by chance alone.

•Important in small populations.

–Founder Effect - Few individuals found new population (Small allelic pool).

–Bottleneck Effect - Drastic reduction in population, and gene pool size.

Five Agents of Evolutionary Change

•Selection

–Artificial - Breeders exert selection.

–Natural - Nature exerts selection.

•Variation must exist among individuals.

•Variation must result in differences in numbers of viable offspring produced.

•Variation must be genetically inherited.

–Natural Selection is a process, and Evolution is an outcome.

Five Agents of Evolutionary Change

•Selection Pressures:

–Avoiding Predators

–Climate

–Pesticides