Evolution of Populations: Part I

Gene Pools Gene Pool: combined genetic information of all members of a particular population. Relative Frequency of an Allele = number of times that allele occurs in a gene pool

2 Main Sources of Genetic Variation 1. mutations 2. Genetic Shuffling during sexual reproduction

Single-Gene Vs. Polygenic Traits Many Possible Phenotypes Trait controlled by two or more genes Two or more alleles 2 Distinct Phenotypes Trait controlled by one gene Two possible alleles

Natural Selection and Phenotypes Natural Selection can affect the distribution of phenotypes in three ways: 1. Directional Selection 2. Stabilizing Selection 3. Disruptive Selection

Directional selection: Individuals at one end of the curve have higher fitness than individuals in the middle or at the end.

Stabilizing Selection: When individuals near the center of the curve have higher fitness than individuals at either end of the curve.

Disruptive Selection: When individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle.