1. Add to table of contents
Speciation graphs Pg. 66
Speciation Pg. 67

2. Speciation Pg. 67 1. Speciation – the formation of a new species.

3. A. Geographic isolation – a physical barrier stops species from interbreeding. Ex. Grand Canyon squirrels. Desert tortoise and a new freeway

4. B. Reproductive isolation – 2 groups within a population become genetically different so they can’t interbreed.
Ex. Frogs that mate at different times.

5. 2. Population Genetics: the study of evolution from a genetic viewpoint.
Most populations have variation amongst their traits.
i.e. different heights, skin color, etc.
If graphed, looks like a bell

6. . Natural Selection can cause a shift in traits within a population.
Depends on which traits are favorable in that environment.
Those traits will increase over time.

7. 4 Different Effects:
A. Stabilizing selection – individuals with the average form have the highest fitness.
ex. Fur color

8. B. Directional selection – individuals with 1 extreme variation have greater fitness than the others.

9. C. Disruptive selection – individuals with either extreme variation have greater fitness than an average.
Can lead to a new species.

10. D. Sexual selection- when female organisms select a mate based on phenotype-May require extreme male traits.
i.e. bright colors, unique mating calls, etc.

11. Go over homework -

13. Rates of speciation:
A. Gradualism – speciation gradually and at a stable rate.

14. Rates of speciation:
B. Punctuated Equilibrium– speciation occurs suddenly, then not at all. Usually due to natural disasters.