Introduction to Population and Evolutionary
Synthetic Theory of Evolution
Described by Sewell Wright
Attempts to explain evolution in terms of changes in gene frequencies
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
Gradually the light-colored moth was attacked and that allele became much
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.