Chapter 16 Evolution of Populations

1. Chapter 16Evolution of Populations Section 16-3The Process of Speciation

2. 16-3 The Process of Speciation • Speciation • The Formation of New Species • Species • A Group of Organisms That Breed With One Another And Produce Fertile Offspring • Individuals In The Same Species Share A Common Gene Pool

3. Isolating Mechanisms Key Concept: As New Species Evolve, Populations Become More Reproductively Isolated From Each Other

4. Isolating Mechanisms ReproductiveIsolation • When Members Of Two Populations Cannot Interbreed And Produce Fertile Offspring • The Populations Have Separate Gene Pools

5. Reproductive Isolation Can Occur Through: • Behavioral Isolation • Geographic Isolation • Temporal Isolation

6. Behavioral Isolation Two or More Populations Are Capable of Interbreeding But Don’t Due To: • Behavior Differences e.g. • Different Courtship Rituals • Other Types of Behavior • Courtship Songs • Courtship Behavior • Sleep/Wake Cycles, etc.

7. Behavioral Isolation Populations May Share Overlapping Territories Eastern Meadowlark WesternMeadowlark Each Species Has Separate Mating Song

8. Geographic Isolation Populations Are Separated By Geographic Barriers e.g. Rivers Mountains Bodies of Water Deserts

9. Geographic Isolation • Grand Canyon Squirrels • Colorado River Formation Of The Grand Canyon Separated Populations Of Abert Squirrels About 10,000 Years Ago. • Separate species – The Kaibab Squirrel Developed

10. Kaibab Abert

11. Temporal Isolation Two Or More Species Reproduce At Separate Times • Three species of Orchids Each Release Pollen On Different Days • Frogs in same pond breed in different months

12. Testing Natural Selection In Nature • Galapagos Finches • Darwin’s Radiation Theory Proven By Peter & Rosemary Grant of Princeton University • Required • Variation • Beak Size Must Change Fitness

13. Testing Natural Selection In Nature Grants Realized Darwin’s Hypothesis Relied On Two Testable Assumptions: • Inheritable Variation Must Be Present In Current Population • Variations Must Produce Enough Differences In Fitness That Natural Selection Will Occur

14. Variation On A Single Island Grant’s Mapped: Populations Breeding Success Wing, Leg, Beak Length Beak Depth & Color Feather Colors Bird Mass They Verified Genetic Variation

15. Natural Selection The Grant's studied finches on Daphne Major, a small island (800 sq. yd) In 1977 island had only 2mm of rain instead of normal 130mm... The drought resulted in a loss of 84% of medium ground finch population. Most died of starvation!

17. Rapid Evolution They Were Able To Document Several Incidences of Rapid Evolution On Daphne Major Over Several Decades

18. Speciation In Darwin’s Finches Key Concept Speciation In The Galapagos Finches Occurred By Founding Of A New Population, Geographic Isolation, Changes In The New Populations Gene Pool, Reproductive Isolation, And Ecological Competition

19. Speciation In Darwin’s Finches

20. Speciation In Darwin’s Finches

21. Speciation In Darwin’s Finches

22. Speciation In Darwin’s Finches A & B Don’t Mate

23. Speciation In Darwin’s Finches

24. Speciation In Darwin’s Finches