There are three main types of natural selection: stabilizing selection, directional selection, and disruptive selection. Stabilizing selection favors average traits so that medium-sized or medium-weight individuals are most likely to survive. Directional selection favors individuals with one extreme trait, like long-necked giraffes or large horses. Disruptive selection favors individuals with opposite extreme traits, so average or intermediate individuals die out while the extremes survive, like with camouflaged light or dark rabbits.

1. Types of Selection (Stabilizing, Directional, Disruptive)

2. Natural Selection Animals adapting to environment Advantaged animals survive and reproduce

3. Stabilizing Selection Most Common Average survives

4. Stabilizing Selection Examples: Short flowers die: No sunlight Medium flowers live: Perfect conditions Tall Flowers die: Wind damage Lightweight babies have higher mortality rate: weaker Average weight babies survive more often: healthy Heavyweight babies have higher mortality rate: when being born

5. Directional Selection One extreme trait is favoured

6. Directional Selection Examples… A long time ago… Short neck giraffes died: could not reach leaves on tree Medium neck giraffes died: could not reach leaves on tree Long neck giraffes prospered: leaves were reachable A long time ago… Small horses died: very disadvantageous Medium horses died: disadvantageous Large horses prospered: advantageous

7. Disruptive Selection Opposite extreme traits are favoured Average trait is eliminated

8. Disruptive Selection Examples… In an environment with black and white rocks… White rabbit lives: Camouflaged Grey rabbit dies: Seen by predator Black rabbit lives: Camouflaged In an environment with deep and shallow flowers… Short beak hummingbird lives: can get pollen from flower Medium beak hummingbird dies: cannot get pollen from flower Long beak hummingbird lives: can get pollen from flower

9. Video on Types of Selection

11. Works Cited