Introduction to Population and Evolutionary Genetics

Synthetic Theory of Evolution

• Described by Sewell Wright
• Attempts to explain evolution in terms of changes in gene frequencies
• Theory states:

A species evolves when gene frequencies changes and the species moves it to a higher level of adaptation for a specific ecological niche.

• Mutation of alleles and migration of individuals with those new alleles will create variation in the population. Selection will then chose the better adapted individuals and the population will have evolved.

Example: peppered moth in England

• The moth can be either dark or light colored.
• Prior to the industrialization of central England, the light-colored allele was most prevalent. The light-colored moths would hide on the white-barked trees and avoid bird predation.
• But the pollution generated by the new industries stained the light-colored trees dark.
• Gradually the light-colored moth was attacked and that allele became much less prevalent.
• In its place, the dark-colored allele became the most predominant allele because moths that carried that allele could camouflage themselves on the stained trees and avoid being eaten by their bird predators.
• The population had evolved to a higher adaptive condition.