1. CORNELL NOTES: Mechanisms of Evolution

2. Evolution Vocabulary:
Allele: different variations of a gene
Gene Pool: all the different alleles for a gene in a population
Allele Frequency: the number of each type of allele in a population
Genetic Equilibrium: populations that are not evolving

3. Causes of Evolution
1. Natural Selection: organisms with favorable traits for their environment survive and reproduce

4. Causes of Evolution
2. Non-random mating: organisms who choose their mates based on desirable/attractive traits, such as size, strength, or coloration

5. Causes of Evolution 3. Genetic Drift and Small Population Size:
Six-Finger Dwarfism in Old Amish
Causes of Evolution
3. Genetic Drift and
Small Population Size:
In small populations, individuals may leave more descendents than others, just by chance. Over time, these chance occurrences may cause an allele to become more or less common in the population.
How does Genetic Drift happen?
1. Bottleneck Effect: Survivors of a disaster or a disease carry different genes from the original population.
2. Founder Effect: When a few individuals colonize a new habitat they may carry different genes from the original population.

6. Causes of Evolution
4. Gene Flow: Immigration/Emigration: moving into an area/exiting an area and bringing/removing alleles from an area

7. Causes of Evolution
5. Mutations: Changes in a DNA sequence. These changes are favorable, so they get passed on throughout the population in the following generations

8. Mechanisms for Evolution: The Case of The Polydactyl Cats