Patterns of selection - Stabilizing selection, Directional selection & Disruptive selection

Example of Disruptive Selection

- Insects that live on plants with dark green or light green leaves - Medium green insects will be noticed and eaten by predators.

Types of Patterns of Selections

1- Stabilizing Selection 2- Directional Selection 3- Disruptive Selection

Example of Stabilizing Selection

Brown mice selected for, white and black selected against - White and black are more likely to be noticed and eaten by predators. - Over time the population will have mostly brown mice.

Example of Directional Selection

Insecticide use will select for individuals that are resistant. - Originally there were probably only a few resistant individuals. - After several generations, the population will contain mostly resistant individuals.

Disruptive Selection

Occurs when both extremes of a range of characteristic is selected for. The intermediate is selected against.

Stabilizing Selection

Occurs when individuals at the extremes of the range of characteristic are selected against. This means that the "average" individuals are selected for.

Directional Selection

Occurs when individuals of one extreme of the range of characteristic are selected for. Usually occurs when the environment is changing