Evolution in Action

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. Variations • Remember Variations are from: • Mutation – main source of creating unique genes • Gene Shuffling (why you and your siblings may not look alike)

4. 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

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

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

7. 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

8. 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

9. Patterns of Evolution • Divergent Evolution – descendants of a common ancestor evolve in separate species to fit different parts of the enivronment • 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

10. 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

11. 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

12. 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)

13. 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

14. 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!

15. 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.

16. 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