The Process of Speciation

1. The Process of Speciation Objectives: Define species and speciation. Explain 4 isolating mechanisms that result in speciation. Describe how natural selection has been tested in nature. Explain how the speciation of the Galapagos finches occurred.

2. Remember… • Natural selection and chance events can change the relative frequencies of alleles in a population.

3. But… • How does natural selection lead to speciation, the formation of a new species?

4. What’s a species? • A species is a group of organisms that can breed with each other and produce fertile offspring.

5. What must happen for a new species to evolve? • Populations of organisms must become reproductively isolated from each other. • Reproductive isolation is when the members of two populations cannot interbreed and produce fertile offspring.

6. Hybrid Animals…

7. Three ways in which reproductive isolation can occur… • Behavioral isolation • Geographic isolation • Temporal isolation

8. Behavioral Isolation • When two species are capable of interbreeding but have differences in behavior.

9. Behavioral Isolation • Eastern Meadowlark Western Meadowlark

10. Geographic Isolation • When populations are separated by geographic barriers such as rivers or mountains.

11. Geographic Isolation • Abert’s Squirrel Kaibab Squirrel

12. Temporal Isolation • When populations reproduce at different times.

13. Testing Natural Selection • Does natural selection really happen? • Can it actually lead to speciation?

14. Galapagos Finches

15. What do we need? • Natural Variation

16. Beak Size & Survival

17. Change over time • Increase in beak size during drought

18. Speciation in Galapagos Finches • Galapagos Islands South America

19. Speciation in Galapagos Finches