1. Directional Selection Stabilizing Selection Disruptive Selection
Selection Pressures
Directional Selection
Stabilizing Selection
Disruptive Selection

2. Selection Pressures
Directional Selection – takes place when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end

3. Selection Pressures
Stabilizing Selection – takes place when individuals near the center of the curve have higher fitness than individuals at either end of the curve

4. Selection Pressures
Disruptive Selection – takes place when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle

5. So What is a Selection Pressure?
…a pressure that drives the variation in a population.