1. End Show Slide 1 of 33 Copyright Pearson Prentice Hall Biology

2. End Show Slide 2 of 33 Copyright Pearson Prentice Hall 16-3 The Process of Speciation

3. End Show 16-3 The Process of Speciation Slide 3 of 33 Copyright Pearson Prentice Hall 16-3 The Process of Speciation Natural selection and chance events can change the relative frequencies of alleles in a population and lead to speciation. Speciation is the formation of new species. A species is a group of organisms that breed with one another and produce fertile offspring.

4. End Show 16-3 The Process of Speciation Slide 4 of 33 Populations share a common gene pool. A genetic change occurring in a single individual can spread through a population as individuals and their offspring reproduce. If genetic change is beneficial, increasing fitness, that gene will eventually be found in many individuals within the population. (remember the lizards from section 2) Copyright Pearson Prentice Hall

5. End Show 16-3 The Process of Speciation Slide 5 of 33 Copyright Pearson Prentice Hall Isolating Mechanisms What factors are involved in the formation of new species? The gene pools of two populations must become separated for them to become new species.

6. End Show 16-3 The Process of Speciation Slide 6 of 33 Copyright Pearson Prentice Hall Isolating Mechanisms As new species evolve, populations become reproductively isolated from each other. When the members of two populations cannot interbreed and produce fertile offspring, reproductive isolation has occurred.

7. End Show 16-3 The Process of Speciation Slide 7 of 33 Reproductive Isolation can develop in a variety of ways –Behavioral Isolation –Geographic Isolation –Temporal Isolation Copyright Pearson Prentice Hall

8. End Show 16-3 The Process of Speciation Slide 8 of 33 Copyright Pearson Prentice Hall Isolating Mechanisms Behavioral Isolation Behavioral isolation occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior.

9. End Show 16-3 The Process of Speciation Slide 9 of 33 Ex: Eastern and Western Meadowlarks in the US. –Similar birds whose habitat overlaps but they do not mate because they use different songs to attract males. Copyright Pearson Prentice Hall

10. End Show 16-3 The Process of Speciation Slide 10 of 33 Copyright Pearson Prentice Hall Isolating Mechanisms Geographic Isolation Geographic isolation occurs when two populations are separated by geographic barriers such as rivers or mountains. Abert Kaibab

11. End Show 16-3 The Process of Speciation Slide 11 of 33 Ex.: about 10,000 years ago the Colorado River separated the Abert squirrels creating two separate populations. –Created 2 gene pools. –Genetic changes in one group did not occur in the other –Natural selection work separately on each group which led to the formation of a distinct subspecies, the Kaibab squirrel. Copyright Pearson Prentice Hall

12. End Show 16-3 The Process of Speciation Slide 12 of 33 Geographic barriers do not guarantee the formation of a new species –If 2 species are separated, then rejoined and they can still interbreed they remain a single species. –A large river may separate small land animals but would not isolate a bird population. Copyright Pearson Prentice Hall

13. End Show 16-3 The Process of Speciation Slide 13 of 33 Copyright Pearson Prentice Hall Isolating Mechanisms Temporal Isolation Temporal isolation occurs when two or more species reproduce at different times.

14. End Show 16-3 The Process of Speciation Slide 14 of 33 Copyright Pearson Prentice Hall Testing Natural Selection in Nature Studies showing natural selection in action involve descendants of the finches that Darwin observed in the Galápagos Islands. The finches Darwin saw were different, but he hypothesized that they had descended from a common ancestor.

15. End Show 16-3 The Process of Speciation Slide 15 of 33 Copyright Pearson Prentice Hall Testing Natural Selection in Nature

16. End Show 16-3 The Process of Speciation Slide 16 of 33 Copyright Pearson Prentice Hall Testing Natural Selection in Nature

17. End Show 16-3 The Process of Speciation Slide 17 of 33 Copyright Pearson Prentice Hall Testing Natural Selection in Nature Peter and Rosemary Grant tested Darwin’s hypothesis, which relied on two testable assumptions: For beak size and shape to evolve, there must be enough heritable variation in those traits to provide raw material for natural selection. Differences in beak size and shape must produce differences in fitness, causing natural selection to occur.

18. End Show 16-3 The Process of Speciation Slide 18 of 33 Copyright Pearson Prentice Hall Testing Natural Selection in Nature When food was scarce, individuals with large beaks were more likely to survive.

19. End Show 16-3 The Process of Speciation Slide 19 of 33 Copyright Pearson Prentice Hall Speciation in Darwin's Finches Speciation in the Galápagos finches occurred by: founding of a new population geographic isolation changes in new population's gene pool reproductive isolation ecological competition

20. End Show 16-3 The Process of Speciation Slide 20 of 33 Copyright Pearson Prentice Hall Speciation in Darwin's Finches Founders Arrive A few finches— species A—travel from South America to one of the Galápagos Islands. There, they survive and reproduce.

21. End Show 16-3 The Process of Speciation Slide 21 of 33 Copyright Pearson Prentice Hall Speciation in Darwin's Finches Geographic Isolation Some birds from species A cross to a second island. The two populations no longer share a gene pool.

22. End Show 16-3 The Process of Speciation Slide 22 of 33 Copyright Pearson Prentice Hall Speciation in Darwin's Finches Changes in the Gene Pool Seed sizes on the second island favor birds with large beaks. The population on the second island evolves into population B, with larger beaks.

23. End Show 16-3 The Process of Speciation Slide 23 of 33 Copyright Pearson Prentice Hall Speciation in Darwin's Finches Reproductive Isolation If population B birds cross back to the first island, they will not mate with birds from population A. Populations A and B are separate species.

24. End Show 16-3 The Process of Speciation Slide 24 of 33 Ecological competition –When 2 species live in the same environment, they compete with each other for available seeds. –More specialized birds have less competition for certain kinds of food and the competition decrease for other birds. Over time species will evolve in a way that increases their differences Copyright Pearson Prentice Hall

25. End Show - or - Continue to: Click to Launch: Slide 25 of 33 Copyright Pearson Prentice Hall 16-3

26. End Show Slide 26 of 33 Copyright Pearson Prentice Hall 16-3 When two species do not reproduce because of differences in mating rituals, the situation is referred to as a.temporal isolation. b.geographic isolation. c.behavioral isolation. d.reproductive isolation.

27. End Show Slide 27 of 33 Copyright Pearson Prentice Hall 16-3 The most important factor involved in the evolution of the Kaibab and Abert squirrels of the American Southwest appears to be a.temporal isolation. b.geographic isolation. c.behavioral isolation. d.different food sources.

28. End Show Slide 28 of 33 Copyright Pearson Prentice Hall 16-3 One finding of the Grants' research on generations of Galápagos finches was that a.natural selection did not occur in the finches b.natural selection can take place often and very rapidly. c.beak size had no effect on survival rate of the finches. d.natural selection was slow and permanent.

29. End Show Slide 29 of 33 Copyright Pearson Prentice Hall 16-3 All of the following played a role in speciation of Galápagos finches EXCEPT a.no changes in the gene pool. b.separation of populations. c.reproductive isolation. d.natural selection.

30. End Show Slide 30 of 33 Copyright Pearson Prentice Hall 16-3 Beak size in the various groups of Galápagos finches changed primarily in response to a.climate. b.mating preference. c.food source. d.availability of water.

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