Evolution and Speciation

1. Evolution and Speciation Biology Miss Schwippert Evolution

2. Definitions Chapter 16 16.1 Gene pool Relative frequency Single gene trait Polygenic trait 16.2 Directional selection Stabilizing selection Disruptive selection Genetic drift Founder effect Hardy- Weinberg principal Genetic equilibrium 16.3 Speciation Reproductive isolation Behavioral isolation Geographic isolation Temporal isolation

3. Speciation • Species- a group of individuals that breed and produce fertile offspring • What a about a Liger? A Mule?

4. What is Speciation • Speciation: is a lineage- splitting even that produces one or more new species • formation of new species

5. Causes of Speciation • As new species evolve, populations become reproductively isolated from each other • Reproductive isolation- occurrence in which the members of two populations cannot interbreed and produce fertile offspring • Populations have separate gene pools

6. Geographic Isolation • Geographic Isolation- two populations are separated by geographic barriers • i.e. rivers, mountains, or bodies of water • Kaibab and Albert squirrels (Colorado River) • May not isolate all species (bird populations) • Two populations can no longer interbreed • Genetic Divergence and differences occur

8. Causes of Speciation • Behavioral Isolation- occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior • Bird songs • Temporal Isolation- two or more species reproduce at different times • Orchid pollen release

9. Genetic Drift Natural selection is not the only source of evolutionary change Genetics controlled by laws of probability In smaller pops, the results may be further from laws of probability Genetic drift- random change in allele frequencies that occurs in small populations

10. Genetic Drift • By Chance- Certain individuals might leave more offspring (alleles that others) • Over Time- an allele can become more and more common • founder effect- a situation in which allele frequencies change as a result of the migration of a small subgroup of a population

11. Causes of Speciation • Selective Pressure: • Directional Selection • Stabilizing Selection • Disruptive Selection

12. Directional Selection • Directional selection- when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end • Results in directional change

13. Stabilizing Selection • Stabilizing selection- when individuals near the center of the curve have higher fitness than individuals at either end of the curve • When extremes are selected

14. Disruptive Selection • Disruptive selection- when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle • Extremes are selected for • Very uncommon

15. Adaptive Radiation • Individuals will diversify rapidly to fit a NITCH in the environment • Usually due to change in the environment • New Resources= new niches to fill

17. Convergent Evolution • Different Species Evolve similar ways • Example: analogous trait- Same function/ NOT related

18. Co evolution • TWO or more populations that evolve together over an extended period of time • They adapt with each other • Usually work together

19. Phylogeny • Evolutionary “Tree” of a species • Shows Branching • Shows Common Ancestors!

20. Cladogram • Based on relations • Not a tree because it does NOT show a common ancestor • The further from divergence, the less relates • Who is the most commonly related here?

21. Rates of Evolution • Gradualism- gradual change over a long period of time eventually forms a new species • Isolationism or gradual climate change

22. Rate of Evolution • Punctuated equilibrium- periods of rapid change, separated by periods of little or no change • Extinction • Catastrophic events