Exam 24: Species and Speciation

Which of the following factors is most likely to produce a reproductive barrier in a single population?

Which of the following characteristics is a postzygotic barrier that prevents hybrids between two species from producing offspring?

Which of the following factors would not contribute to allopatric speciation?

A female fly, full of fertilized eggs, is swept by high winds to an island far from the mainland. She is the first, and only, fly to arrive on this island. Thousands of years later, her numerous offspring occupy the island, but none of them resembles her. There are, instead, several species and their geographic ranges overlap. Each species eats a different kind of food. None of the species can fly and the balancing organs of males differ among species and are now used in courtship displays. Fly species W produces fertile offspring with species Y, but not with species X or Z. Furthermore, X and Z do not hybridize. Which of the following statements about species W and Y is most likely to be accurate?

Which of the following conditions is most likely to reinforce isolating mechanisms between two species that occasionally hybridize?

Almost all peppered moths in England were light colored before the Industrial Revolution. However, some dark forms were collected-the dark color is determined by a single, dominant allele of one gene. The bark of trees became darker during the Industrial Revolution in areas where heavy coal use in factories caused pollution. By about 1900, approximately 90% of the moths around industrial areas were dark, whereas light-colored moths were still abundant elsewhere. Apparently, birds could readily find the light moths against the dark trees in industrial areas and, therefore, were eating more light moths. Recently, use of cleaner fuels has resulted in tree bark becoming lighter again and the dark-colored moths have been disappearing. Which of the following statements best explains whether we should consider the forms different species?

Which of the following factors is the primary criterion for determining species boundaries when applying the biological species concept?

Which of the following factors most likely accounts for the fact that polyploids are much more common in plants than in animals?

Which of the various species concepts distinguishes two species based on the degree of genetic exchange between their gene pools?

Two species of frogs belonging to the same genus occasionally mate, but the embryos stop developing after a day and then die. Which of the following mechanisms keep the species separate?

The common edible frog of Europe is a hybrid between two named species, Rana lessonae and Rana ridibunda. The hybrids were first described in 1758 and have a wide distribution, from France across central Europe to Russia. Both male and female hybrids exist, but when they mate among themselves, they rarely produce offspring. Which of the following statements is the best inference about the two Rana species?

The largest unit within which gene flow can readily occur is a ________.

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?

Which of the following statements is the best definition of a hybrid zone?

Two populations of birds with somewhat different coloration live on opposite sides of a peninsula. The habitat between the populations is not suitable for these birds. When birds from the two populations are brought together in captivity, they interbreed and produce fertile young whose appearance is intermediate between the two parents. In the wild, the two populations remain separate as a result of which of the following factors?

If biological species are defined in terms of reproductive compatibility, which of the following factors determines the formation of a new species?

According to the punctuated equilibria model, ________.

Plant species A has a diploid chromosome number of 12. Plant species B has a diploid number of 16. A new species, C, arises as an allopolyploid from A and B. The diploid number for species C would probably be ________.

Which of the following outcomes is most likely in hybrid zones where reinforcement of isolating mechanisms is occurring?

In the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp, 15 species on the Pacific side and 15 different species on the Atlantic side. Species live at different water depths. Morphological and genetic data show that Atlantic and Pacific species that live at similar depths are sister species. The sister species on each side of the isthmus cannot interbreed because the water in the canal is fresh water, not salt water, and provides a barrier to reproduction. A sea-level, salt-water canal between the two oceans has been proposed to make transport across the isthmus easier. Which of the following outcomes is the most likely result if such a canal were built?