Copyright Pearson Prentice Hall Biology Copyright Pearson Prentice Hall

16-3 The Process of Speciation Photo credit: ©MURRAY, PATTI/Animals Animals Enterprises Copyright Pearson Prentice Hall

16-3 The Process of Speciation Speciation is the formation of new species. Chance Natural selection A species is a group of organisms that breed with one another and produce fertile offspring. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Isolating Mechanisms Isolating Mechanisms As new species evolve, populations become reproductively isolated from each other (gene pools must be separated) When the members of two populations cannot interbreed and produce fertile offspring, reproductive isolation has occurred. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Isolating Mechanisms 1. Behavioral Isolation (sympatric)  Behavioral isolation occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Isolating Mechanisms 2. Geographic Isolation (allopatric) Geographic isolation occurs when two populations are separated by geographic barriers such as rivers or mountains. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Isolating Mechanisms 3. Temporal Isolation (sympatric)  Temporal isolation occurs when two or more species reproduce at different times. Copyright Pearson Prentice Hall

Testing Natural Selection in Nature Finches in the Galapagos Islands Honey Creepers in Hawaii Copyright Pearson Prentice Hall

Testing Natural Selection in Nature Detailed genetic studies have shown that these finches evolved from a species with a more-or-less general-purpose beak.  Copyright Pearson Prentice Hall

Testing Natural Selection in Nature Detailed genetic studies have shown that these finches evolved from a species with a more-or-less general-purpose beak.  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. Copyright Pearson Prentice Hall

Testing Natural Selection in Nature When food was scarce, individuals with large beaks were more likely to survive. This graph shows the survival rate of one species of ground-feeding finches, the medium ground finch.  Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 16-3 When two species do not reproduce because of differences in mating rituals, the situation is referred to as temporal isolation. geographic isolation. behavioral isolation. reproductive isolation. Copyright Pearson Prentice Hall

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 temporal isolation. geographic isolation. behavioral isolation. different food sources. Copyright Pearson Prentice Hall

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

Copyright Pearson Prentice Hall 16-3 All of the following played a role in speciation of Galápagos finches EXCEPT no changes in the gene pool. separation of populations. reproductive isolation. natural selection. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 16-3 Beak size in the various groups of Galápagos finches changed primarily in response to climate. mating preference. food source. availability of water. Copyright Pearson Prentice Hall

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