1. Biology Chapter 11 Notes

2. Gene pool- the combined alleles of all the individuals in a population Allele frequency- a measure of how common a certain allele is in the population Genetic variation

3. Phenotypes near the middle of the range tend to be more common, while the extremes are less common. Normal distribution

4. A type of selection that favors phenotypes at one extreme of a trait’s range. Ex: low drug resistant bacteria to high drug resistant bacteria Directional selection

5. The intermediate phenotype is favored and becomes more common in the population. Ex: wasps feed on small gall flies and woodpeckers feed on large gall flies Stabilizing selection

6. When both extreme phenotypes are favored by selection Ex: blue- blue brown- dull brown lazuli buntings Blue is dominant and see the other blue & blue brown as threats, leave the dull brown alone Disruptive selection

7. Gene flow- the movement of alleles from one population to another Genetic drift- changes in allele frequency that are due to chance Mechanisms of evolution

8. Genetic drift that occurs after an event greatly reduces the size of a population Ex: over hunting Bottleneck effect

9. Genetic drift that occurs after a small number of individuals colonize a new area. Ex: dwarfism in old order Amish communities Founder effect

10. Reproductive isolation occurs when members of different populations can no longer mate successfully with one another. Speciation is the rise of two or more species from one existing species Speciation through Isolation

11. Courtship dances, chemical scents, and courtship songs are signals for mating between populations Behavioral isolation is caused by differences in these behaviors Behavioral isolation

12. Other isolations

13. Different species often must adapt to similar environments. Evolution toward similar characteristics in unrelated species is called convergent evolution. Convergent evolution

14. When closely related species evolve in different directions. Divergent evolution

15. Episodes of speciation occur suddenly in geologic time and are followed by long periods of little evolutionary changes Punctuated equilibrium