Chapter 17: Speciation

Which of the following is least likely to lead to allopatric isolation? A. A hill dividing a population of desert-dwelling mice B. A deep gorge dividing a population of slow-moving snails C. A land bridge dividing a population of tuna D. A river dividing a population of small crickets E. A small lake dividing a population of butterflies

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 A. allopatric speciation. B. the early stages of extinction. C. sympatric speciation. D. the formation of new species by polyploidy. E. speciation due to directional selection.

Which statement about polyploidy in plants is true? A. Polyploid plants are usually less vigorous than diploid plants of the same species. B.Tetraploid and diploid plants of a given species can mate to produce viable triploid offspring. C. Allopolyploids are hybrid plants that result from the mating of two closely related species. D. Tetraploid plants can mate with other tetraploid plants of the same species, but not with themselves. E. Polyploidy is rare in plants.

Darwin's finches on the Galápagos Islands have diverged primarily via _______ speciation, and exhibit diverse morphologies owing to differences in ________. A. sympatric; predation pressures B. allopatric; predation pressures C. sympatric; their diets D. allopatric; their diets E. allopatric; drought tolerance adaptations

Prezygotic isolating mechanisms can arise from all of the following except A. mate selection behaviors. B. evolution of the structure of sexual organs. C. differences in mating periods. D. specific interactions of plants with insect pollinators. E. low fertility of hybrids.

Which species concept most emphasizes the evolutionary history of species? A. The morphological species concept B. The cryptic species concept C. Mayr's biological species concept D. The polyploidy species concept E. The lineage species concept

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 A. aabb. B. aaBb. C. aaBB. D. Aabb. E. AaBb.

The distinction between prezygotic and postzygotic isolation is whether A. polyploidy is involved. B. reinforcement is involved. C. selection directly favors the reproductive isolation. D. the isolation occurs before or after fertilization. E. the isolation occurs before or after mating.

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 _______. A. more; increase; gametic isolation B. less; increase; gametic isolation C. more; decrease; gametic isolation D. more; increase; reinforcement E. less; decrease; reinforcement

Which sequence of events is most likely in allopatric isolation? A. Geographic barrier, reproductive isolation, genetic divergence B. Geographic barrier, genetic divergence, reproductive isolation C. Reproductive isolation, genetic divergence, geographic barrier D. Genetic divergence, reproductive isolation, geographic barrier E. Genetic divergence, geographic barrier, reproductive isolation

Which statement is true? - Ernst Mayr's biological species concept A. is based only on morphological characters. B. applies only to groups of organisms living in the same areas. C. applies only to animals. D. applies to all organisms. E. does not apply to organisms that reproduce asexually.

The Dobzhansky-Muller model A. is based on the morphological species concept. B. cannot be applied to chromosomal rearrangements. C. cannot be applied to cryptic species. D. emphasizes gene interaction. E. is an explanation for the origin of physical barriers that separate species.

Two populations that were once isolated come into contact. Which of the following statements about what might happen after contact is false? A. If hybrids are unfit, then prezygotic barriers would not be reinforced. B. Hybrid zones that last for long periods of time could develop. C. Hybrids, if fit, could spread through both populations, resulting in gene flow between them. D. If reproductive isolation had been established before contact, the two populations could not interbreed. E. If reproductive isolation is not complete, the two populations could interbreed.

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? A. Eventually, all members of both populations would be hybrids. B. Because their hybrid offspring are not reproductively fit, reinforcement could strengthen postzygotic barriers. C. Because their hybrid offspring are not reproductively fit, reinforcement could strengthen prezygotic barriers. D. The hybrid offspring would mate with other hybrid offspring to produce viable offspring. E. The hybrid offspring (mules) would become widespread and mate with members of both populations.

Geographic isolation A. is required for speciation. B. may decrease the probability, over time, that members of two separated populations can mate. C. has the same effects on all organisms. D. always results in reproductive isolation. E. always results in the formation of new species.

Which is least likely to evolve via direct natural selection?A. Hybrid infertility B. Behavioral isolation C. Mechanical isolation D. Habitat isolation E. Temporal isolation

All of the following statements about speciation are true except A. the Dobzhansky-Muller model is based on a minimum of two gene loci. B. gene flow within a population must be interrupted for speciation to occur. C. chromosomal rearrangements can lead to speciation. D. evolution always results in speciation. E. reproductive isolation may take millions of years.

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. A. behavioral B. habitat C. temporal D. gametic E. mechanical

Which statement about the morphological species concept is true? A. It is easily applicable to cryptic species. B. Linneaus used one. C. It is most applicable when there is variation within species. D. It emphasizes the potential to interbreed. E. It emphasizes ancestor-descendant relationships.

Persistent hybrid zones, like those found in Bombina frogs in Europe, stay narrow due to A. hybrid infertility. B. low hybrid adult viability. C. habitat isolation. D. behavioral isolation. E. temporal isolation.