Evolution and Speciation

1. Evolution and Speciation

2. Gene Flow • Gene flow- allele frequencies are changed by organisms migrating in and out of populations

3. Genetic Drift • Genetic drift- chance events that change allele frequencies (2 types) • Bottle Neck affect- a sudden random event in the environment can cause the population size to drop

4. Genetic Drift • Founder affect- a small portion of the populations is isolated and starts a new gene pool

5. Mutations • Mutations- random changes in DNA can change allele frequencies**

6. Speciation -speciation- the evolution of a new species -species- organisms capable of interbreeding and producing healthy, fertile offspring

7. Speciation Categories • Allopatric Speciation- speciation due to geographic isolation (most common) • Sympatric Speciation- speciation, despite living in the same geographic area

8. Speciation -geographic isolation- when a physical barrier divides a population, creating a new species. (ex. Lava, earthquakes, etc)

9. Speciation • Reduced Hybrid Fertility- Two species can mate, but offspring are not capable of reproduction. (sterile)

10. Speciation • Behavioral Isolation- behaviors such as different courtship rituals prevent two species from mating

11. Speciation -mechanical isolation- morphological differences prevent species from reproducing

12. Speciation • Temporal Isolation- The time line of breeding prevents species from mating. They mate during different times of day or seasons.

13. Speciation • Gametic Isolation – Incompatible gametes prevent two species from mating. (internal conditions vary, or gamete proteins don’t recognize one another)

14. Speciation • Reduced Hybrid Viability- Two species can mate, but offspring are not healthy and die.

15. Speciation • Hybrid Breakdown- Two species can mate, but when the Hybrids have offspring, the offspring are either sterile or unhealthy ( no grandkids)

16. Patterns of evolution Gradualism- evolution happens slowly over time Punctuated equilibrium- evolution happens in quick bursts with long periods of no evolution in between.

17. Patterns of Evolution Divergent evolution -(adaptive radiation)- species with a common ancestor become increasingly different (homologous)

18. Patterns of Evolution Convergent evolution- unrelated species become similar (analogous)

19. Patterns of Evolution Co-evolution- species evolve in response to each other