1. Evolution in Action

2. Vocab to start
Gene Pool: consists of all genes including all of the different alleles present in a population
Relative Frequency: how often that allele appears in a population (expressed as a percentage)
* EVOLUTION IS A CHANGE IN THE GENE FREQUENCY*

3. Genetic Equilibrium
Allele frequencies will remain constant unless factors cause it to change
Factors to keep frequencies constant:
Random Mating (all members have equal chances)
Large Populations (small populations undergo genetic drift)
No immigration or emigration (moving into or out of the population)
No mutations (that would make new alleles!)
No natural selection (all should have equal chance of survival!)
Genetic Equilibrium-CONSTANT!!!!...NO Evolution

4. Disrupting Equilibrium
Mutations – Create unique new genes
Gene Flow – genes move from one population to another because mating happens between them

5. Disrupting Equilibrium Cont’d
Genetic Drift – Allele frequencies change as a result of random events or chance (in small populations, one organism not reproducing can have a large effect!)

6. Disrupting Equilibrium Cont’d
Non- Random Mating
Mating with a related organism
Assortive mating – mating with an organism that has similar traits
Sexual Selection – females choose mates based on certain traits

7. Patterns of Evolution
Convergent Evolution – Different species evolve similar traits
Come from different ancestors
Similar adaptations for similar environments
Example: Anole Lizards in Caribbean – all species that live on twigs had thin bodies – DNA shows they do not have a common ancestor

8. Patterns of Evolution
Divergent Evolution – descendants of a common ancestor evolve in separate species to fit different parts of the environment
Come from common ancestors
Example: Anoles on the same island that are closely related but have differences because come live on land (small toe pads and quick) and some in trees (large toe pads but slow)
Adaptive Radiation – a new population in a new environment undergoes divergent evolution until it fills the different niches of the environment
Example: Darwin’s Finches

9. Patterns of Evolution
Coevolution- Two organisms that have a close ecological relationship affect the evolution of each other
Example: Plants and Pollinators, Humans and antibiotic resistant bacteria

10. Types of Selection on Polygenic Traits
Stabilizing Selection
Nature favors the average trait and chooses against the extremes
Disruptive Selection
Nature favors both extremes but not the average trait.
Directional Selection
Nature favors one of the extremes

11. Speciation!
Species = similar group of organisms that can reproduce and create fertile offspring.
Speciation = creating a new species
Ways to become reproductively isolated (can’t breed!):
Behavioral
Geographic
Temporal (time)

12. Behavioral Reproductive Isolation
Capable of interbreeding but differences in courtship or reproductive strategies
Examples: Eastern and Western Meadow Larks use different songs to attract mates so they will never breed together

13. Geographic Reproductive Isolation
Species can’t mate because they are separated by barriers like mountains or rivers.
Example: Kaibab and Abert squirrels are separated by the Grand Canyon and have many different features.
Finches as well!

14. Temporal Reproductive Isolation
Species can’t mate because reproduction happens at different times of the year.
Example: Orchids in the rain forest where flowers only last a day and wither all flower at separate times.

15. Rate of Speciation
Gradualism – speciation occurs at a regular or gradual rate
Punctuated Equilibrium – speciation happens in bursts – everything is in equilibrium for a while and then short periods of time show rapid change