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Chapter 16: Mechanisms of Speciation

Chapter Study Questions

Chapter Study Questions


This activity contains 11 questions.

	Match the key terms in this chapter listed below with the phrase that is the best match for it. Using the pull-down menus, match each item in the left column to the corresponding item in the right column. reinforcement cryptic species biological species concept morphospecies concept species phylogenetic species concept 1.1 the smallest evolutionarily independent unit A B C D E F 1.2 a concept of distinguishing species based on their phenotypes A B C D E F 1.3 a concept of distinguishing species based on whether or not they interbreed regularly with each other A B C D E F 1.4 a concept of distinguishing species by finding the smallest monophyletic group on a phylogeny A B C D E F 1.5 species that are evolutionarily independent from each other, but are not distinguishable based on morphology A B C D E F 1.6 selection for reproductive isolation by means of reduced fitness of hybrids A B C D E F

	Briefly describe the classic view of how speciation occurs. What three things have to happen for one species to split into two? Do these three steps always occur separately and in the same order?   To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

	The most important evolutionary force causing genetic divergence of separated populations is _________.   natural selection genetic drift mutation

	Apple maggot flies (Rhagoletis) have recently evolved an "apple race" that has distinctive alleles related to the timing of apple fruiting. What statement below can also factually be stated about apple maggot flies?   They have recently divided into two populations which still experience some gene flow. They probably are evolving by the process of genetic drift. They are an example of allopatric speciation in action. They probably are dividing into two populations because they are highly sedentary and incapable of flying between different trees. They originally evolved on apple trees, but have recently adapted to use hawthorn trees.

	Describe the unusual mating behavior of Drosophila heteroneur. Why are these species thought to have diverged via sexual selection, rather than via natural selection? What is the evidence that sexual selection has played a role? Could natural selection also have played a role?   To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

	Which of the following statements regarding reinforcement are correct?   It is not supported by many field studies or genetic models. It is supported by Coyne & Orr's Drosophila studies showing that prezygotic isolation evolves more rapidly in sympatric than in allopatric species. It can occur when closely related species come back into contact and hybridize, and when hybrids have reduced fitness. It is supported by laboratory research showing that Australian fruit flies evolve differences in mating pheromones when they are kept in close contact with each other. It is essential for speciation.

	Suppose you are studying two related species of lizards, one of which lives in warm lowland deserts and the other in forested mountains. You discover that where the two species' ranges meet, in low-lying, lightly forested woodland, they hybridize. Can you predict the likely evolutionary fate of hybrids, and the parental species? How could you test your ideas?   To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

	Give an example of a particular gene that is known to be linked to a phenotypic trait involved in a natural speciation event.   To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

	Historically, North America has been home to at least two species of large canid. The gray wolf, Canis lupus, existed in forests throughout most of North America, where they preyed on large ungulates such as elk and moose. A second species, the much smaller coyote (Canis latrans), was restricted to the plains and deserts of central North America, where they fed on much smaller prey. Coyotes and wolves were easily and unambiguously distinguishable by morphology. Since 1900, wolves have been almost completely extirpated in the United States, though populations still exist in Canada. Coyotes, in response, enormously increased their range northward and eastward, inhabiting areas that had formerly been inhabited by wolves, and also taking advantage of deforestation and agriculture that turned forested areas into a more open habitat. In 2003, a research team announced the startling discovery that mitochondrial DNA from two old wolf skins - two wolves that were killed in New York State and Maine in the 1800's - did not match mitochondrial DNA of known gray wolves. Both of these animals had mtDNA more similar to that of coyotes than of gray wolves. The mtDNA of the New York wolf nested within coyotes; but the mtDNA of the Maine wolf was on a deep branch near the split of gray wolves and coyotes. Yet the skins, morphologically, appeared unambiguously those of wolves, not coyotes. Part I: What is your interpretation of the results describing wolves in North America above? Part II: Today, due to the scarcity of their own species and the arrival of coyotes, the few wolves left in eastern North America often hybridize with coyotes. As a result, many wolves in eastern North America carry a confusing mixture of wolf and coyote alleles. Similar patterns are seen in another unusual population, the highly endangered "red wolf" of the southeastern United States. Thus, there appears to be a large amount of hybridization occurring in the few surviving wolf populations of North America. In the United States, hybrids are not protected under the endangered species Act. In Ontario, hybrids are given the same protection status as their parent species. Which do you think is the better policy? Part III: Before these genetic discoveries, conservation biologists had been pursuing plans to reintroduce the gray wolf to Maine. Do you think they should proceed with this course of action?   To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

	The diagram below represents the ranges of 3 species (A, B, and C), which are separated by a mountain range and river. Jane B. Geographer has hypothesized that these three species arose via vicariance. Specifically, she has proposed that the area was originally occupied by a single species. Its range was split first by the mountain range. Later, the river formed, separating populations on the eastern side of the mountains. If her hypothesis is correct, phylogenetic analysis should reveal that   All three species are equally related. Species A and C are each other's closest relatives. Species B and C are each other's closest relatives. Species B and A are each other's closest relatives.

	The diagram below represents the ranges of 3 species (A, B, and C), which are separated by a mountain range and river. Joe B. Geographer (Jane's brother) has hypothesized that these species descended from a common ancestor via dispersal. Specifically, he has proposed that the original species was confined to the western side of the mountains. One dispersal event brought individuals around the northern end of the mountains; the river prevented them from dispersing farther south. Some time later, a second dispersal event brought individuals around the southern end of the mountains; dispersal of these individuals was also stopped by the river. If Joe's hypothesis is correct, phylogenetic analysis should reveal that   Species B and C are each other's closest relatives. All three species are equally closely related. Species A and B are each other's closest relatives. Species A and C are each other's closest relatives.

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