1. Population Genetics The science of genetic change in population.
Population – all the members of a species that occupy a particular area at the same time
Gene Pool – all the genes in all the members of a population

2. Genes and Variation Genetics Joins Evolutionary Theory
Variation is the raw material for natural selection
Gene pool – consists of all the genes, including all the different alleles for each gene, that are present in a population
Relative frequency – the number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur
Therefore – evolution is any change in the relative frequency of alleles in the gene pool of a population over time
3 Sources of Genetic Variation
Mutations
Genetic Recombination in Sexual Reproduction (Ind assortment and crossing over)
Lateral Gene Transfer (conjugation)
Single-Gene (2 pheno) vs. Polygenic Traits (many pheno/bell curve)
***Natural Selection acts directly on PHENOTYPES not actual alleles*** some phenotypes are better suited to an environment than others and they will survive, reproduce and pass on their genes.

3. Evolution as Genetic Change in Populations
How Natural Selection Works – 3 Types
Stabilizing Selection
Individuals with the average form of a trait have the highest fitness
Represents the optimum for most traits
Results in a similar morphology between most members of the species
Directional Selection
Individuals that display a more extreme form of a trait have greater fitness than individuals with an average form of the trait
A shift in one direction
Peppered moth
Disruptive Selection
Individuals with either extreme variation of a trait have greater fitness than individuals with the average form of the trait
A shift in both direction, away from the center
Shell color (dark rocks and light sand)

5. Genetic Drift
Random changes in the frequency of a gene in the absence of natural selection  occurs because of CHANCE
Occurs efficiently in small populations because small changes affect more members
Two examples:
a. Bottleneck effect
b. Founder effect

6. a. Bottleneck Effect
Genetic drift (reduction of alleles in a population) resulting from a disaster that drastically reduces population size.
Examples:
1. Earthquakes
2. Volcano’s

7. b. Founder Effect
Genetic drift resulting from the colonization of a new location by a small number of individuals.
Results in random change of the gene pool.
Example:
1. Islands
(first Darwin finch)

8. Hardy-Weinberg Principle
Genetic Equilibrium – situation in which allele frequencies in the gene pool of a population remain constant
The concept that the shuffling of genes that occurs during sexual reproduction, by itself, cannot change the overall genetic makeup of a population.
Shows mathematically and theoretically that there are situations where evolution DOES NOT OCCUR
Seldom achieved in nature

9. Hardy-Weinberg Principle
This principle will be maintained in nature only if ALL five of the following conditions are met:
1. Very large population
2. Isolation from other populations
3. No net mutations
4. Random mating
5. No natural selection
Hardy-Weinberg Principle

10. Species
A group of populations whose individuals have the potential to interbreed and produce viable offspring.

11. Speciation
The evolution of new species. Species that occupy an otherwise unoccupied niche face no competition, they will therefore have a 100% success rate

12. Reproductive Isolation
Any mechanism that impedes two species from producing fertile and/or viable hybrid offspring -factor necessary for the formation of a new species.
Barriers:
1. Geographic (rivers, mountains)
2. Behavorial - differences in courtship behavior
3. Temporal - fertile periods (time)

13. Interpretations of Speciation
Two theories:
1. Gradualist Model (Neo-Darwinian):
Slow changes in species overtime.
2. Punctuated Equilibrium:
Evolution occurs in spurts of relatively rapid change.

14. Macroevolution
The origin of taxonomic groups higher than the species level.

15. Adaptive Radiation aka Divergent Evolution
Emergence of numerous species from a common ancestor introduced to new and diverse environments.
Example:
Darwin’s Finches

16. Darwin’s Finches an example of Adaptive Radiation

17. Convergent Evolution
Species from different evolutionary branches may come to resemble one another if they live in very similar environments.
Example:
1. Ostrich (Africa) and Emu (Australia).
2. Sidewinder (Mojave Desert) and
Horned Viper (Middle East Desert)
3. Shark and Dolphin

18. Coevolution
Evolutionary change, in which one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species.
Example:
1. Acacia ants and acacia trees
2. Humming birds and plants with flowers with long tubes