GENETIC EQUILIBRIUM I Types of Selection pp. 321-325

WHAT IS EQUILIBRIUM? No net change in the population Evolution is likely not occurring

Hardy-Weinberg Principles To stay in equilibrium: No natural selection No mutations No gene flow (no migration) Infinitely large population Mating is random

Most traits follow a normal distribution curve with the average being the peak in the population.

WHAT PUSHES A POPULATION OUT OF EQUILIBRIUM?

I. Natural selection Acts on physical manifestation of trait or behaviors Organisms best suited to their environment live to reproduce and pass on their genes Organisms that reproduce the most offspring have the greatest fitness Varying types of selection

Directional selection: individuals with a more extreme form of trait have higher fitness

Stabilizing selection: having average form of trait has highest fitness

Disruptive selection: individuals with any extreme trait has a higher fitness

Sexual selection: choose mates based on specific traits and those traits increase in the population

Artificial selection