Lectures 22-24.Speciation Study Questions.2013

In particular explain how the phylogenetic

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Unformatted text preview: ater lake cichilds BIS 2B, Spring 2013 Speciation Page 4 _____________________________________________________________________________________ _____________________________________________________________________________________ STUDY QUESTIONS _____________________________________________________________________________________ 1. What is the biological species concept, and what are its main criteria for defining a species? 2. Explain why application of the biological species concept is difficult or impossible in each of the following situations: (a) examples of natural hybridization, (b) the existence of strictly asexual organisms, and (c) disjunct (allopatric) distributions of species. 3. Two closely related grasshopper species occur sympatrically. No hybrids have been reported in nature. However, when an evolutionary biologist brings the two species into the lab, she discovers that they can hybridize to produce fertile offspring. How can you explain these observations? Should the grasshoppers be considered separate species? 4. How does natural selection versus genetic drift act to promote the evolution of intrinsic barriers to gene exchange in allopatric (both vicariance and dispersal modes) versus parapatric versus sympatric models of speciation? 5. Why have island archipelagoes played such an important role in the development of the science of speciation? What lessons have we learned from studies of speciation in places like the Hawaiian Islands? 6. Why do most evolutionary biologists agree that allopatric speciation is common but sympatric speciation is not? Focus your discussion on the fundamental difference between these two alternatives, and why that difference is likely to be important for divergence and the evolution of reproductive isolation. 7. Sympatric speciation is generally thought to be a rare event because sympatry should promote gene flow. Explain clearly the evidence that speciation occurred sympatrically in the crater lake cichilid fish inhabiting Barombi Mbo in Cameroon. In particular, explain how the phylogenetic relationships of the 11 species of cichlids in this lake support the argument for sympatric speciation. How does this contrast with the phylogenetic evidence for vicariant allopatric speciation in snapping shrimp? 8. Compare and contrast, using a phylogeny from lecture or the book, the differences be...
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