Unit 3: Evolution : Chapter 17: Speciation Essay

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Ernst Mayr’s biological species concept
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does not apply to organisms that reproduce asexually.
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Which statement about the morphological species concept is true?
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Linneaus used one.
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Which species concept most emphasizes the evolutionary history of species?
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The lineage species concept
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The Dobzhansky-Muller model
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emphasizes gene interaction.
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In the Dobzhansky-Muller model, an ancestral population (aabb) splits into two lineages. Different mutations produce different new alleles in each population (Aabb in one population, aaBb in the other). All of the following genotypes would be viable except
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AaBb
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All of the following statements about speciation are true except
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chromosomal rearrangements can lead to speciation. gene flow within a population must be interrupted for speciation to occur. reproductive isolation may take millions of years. the Dobzhansky-Muller model is based on a minimum of two gene loci. *evolution always results in speciation.*
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Which of the following is least likely to lead to allopatric isolation?
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A small lake dividing a population of butterflies
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Geographic isolation
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May decrease the probability that two species can mate over time
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Which sequence of events is most likely in allopatric isolation?
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Geographic barrier, genetic divergence, reproductive isolation
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Darwin’s finches on the GalĂĄpagos Islands have diverged primarily via _______ speciation, and exhibit diverse morphologies owing to differences in ________.
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allopatric; their diets
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A butterfly is separating into two different groups—one that lays eggs in the understory of bushes and the other that lays eggs in the tops of bushes. This butterfly species is most likely experiencing
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sympatric speciation.
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Which statement about polyploidy in plants is true?
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Allopolyploids are hybrid plants that result from the mating of two closely related specie
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The distinction between prezygotic and postzygotic isolation is whether
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the isolation occurs before or after fertilization.
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Two geographically separated populations of butterflies begin to diverge in the time of day they are active. One group is active earlier in the day, and the other is active later. If this separation were to continue, it would most likely contribute to _______ isolation.
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temporal
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Prezygotic isolating mechanisms can arise from all of the following except
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low fertility of hybrids.
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Refer to the figure below, which shows the frequencies of mating calls in two frogs in areas where they are in sympatry and areas where they are in allopatry. The mating calls are ______ diverged in regions of sympatry. Based on this result, one might predict that there has been selection to _______ prezygotic isolation in regions of sympatry, a phenomenon known as _______.
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more; increase; reinforcement
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Suppose that the natural ranges of horses and donkeys were to overlap. Which of the following statements best describes what would likely happen to the populations over time?
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The hybrid offspring would mate with other hybrid offspring to produce viable offspring. Because their hybrid offspring are not reproductively fit, reinforcement could strengthen prezygotic barriers.
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wo populations that were once isolated come into contact. Which of the following statements about what might happen after contact is false?
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If reproductive isolation is not complete, the two populations could interbreed. Hybrid zones that last for long periods of time could develop. *If hybrids are unfit, reinforcement of prezygotic barriers would be disfavored.* Hybrids, if fit, could spread through both populations, resulting in gene flow between them. If reproductive isolation had been established before contact, the two populations could not interbreed.
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Which is least likely to evolve via direct natural selection?
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Hybrid infertility
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Persistent hybrid zones, like those found in Bombina frogs in Europe, stay narrow due to
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low hybrid adult viability.

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