1. Evolution as Genetic Change
Subtitle

2. Control of Natural Selection
Natural Selection can affect the distributions of phenotypes in any of three ways:
Directional selection
Stabilizing selection
Disruptive selection

3. Directional Selection
Evolution favors the most fit species.
Causes an increase in the number of individuals with favored trait to one end of a curve.

4. Stabilizing Selection
When individuals with the desirable traits are towards the center of the curve.
Major Point: The extremes don’t survive.

5. When the individuals at the extremes have the highest fitness.
Disruptive Selection
When the individuals at the extremes have the highest fitness.

6. Genetic Drift
In a smaller population, individuals that carry a particular allele may leave more descendants than other individuals, just by chance.
Over time, a series of chance occurrences of this type can cause an allele to become common in a population.
This can be caused by the bottle neck effect.

7. Four things that lead to speciation: Reproductive isolation
Behavioral isolation
Geographic isolation
Temporal isolation

8. Reproductive Isolation
When members of two populations cannot interbreed and produce fertile offspring.

9. Ex. Eastern Meadowlark/Western Meadowlark
Behavioral Isolation
When two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior.
Ex. Eastern Meadowlark/Western Meadowlark
Their songs are different and so don’t reproduce.

10. Two populations are separated by geographic barriers.
Geographic Isolation
Two populations are separated by geographic barriers.
Ex. Rivers, mountains, etc.

11. When two or more species reproduce at different times.
Temporal Isolation
When two or more species reproduce at different times.