Chapter 24 Flashcards

1) Use the following information to answer the question.

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, they produce young whose appearance is intermediate between the two parents. These offspring will breed with each other or with birds from either parent population, and all offspring of these pairings appear intermediate to various degrees.

What keeps the two populations separate?

1. A) temporal reproductive isolation
2. B) lack of hybrid viability
3. C) behavior isolates reproductive activities
4. D) habitat isolation

2) If biological species are defined in terms of reproductive compatibility, the formation of a new species hinges on ________.

1. A) gene flow
2. B) reproductive isolation
3. C) hybrid formation
4. D) gene pool expansion

3) Which of the following statements describes mechanical isolation prezygotic barrier?

1. A) two species live in different habitats
2. B) two species mate at different times
3. C) two species share courtship activities
4. D) two snails have shells that spiral in different directions

4) Three populations of crickets look very similar, but the males have courtship songs that sound different. What function would this difference in song likely serve if the populations came in contact?

1. A) a temporal reproductive isolating mechanism
2. B) a postzygotic isolating mechanism
3. C) a behavioral reproductive isolating mechanism
4. D) a gametic reproductive isolating mechanism

5) Many songbirds breed in North America in the spring and summer, and then migrate to Central and South America in the fall. They spend the winter in these warmer areas where they feed and prepare for the spring migration north and another breeding season. Two hypothetical species of sparrow, A and B, overwinter together in mixed flocks in Costa Rica. In spring, species A goes to the east coast of North America, and species B goes to the west coast. What can you say about the isolating mechanisms of these two species?

1. A) They must have strong postzygotic isolating mechanisms to spend winter in such close proximity.
2. B) They must have strong prezygotic isolating mechanisms to spend winter in such close proximity.
3. C) These two species mate in different climates.
4. D) Reinforcement must be occurring when they winter together.

6) The peppered moth provides a well-known example of natural selection. The light-colored form of the moth was predominant in England before the Industrial Revolution. In the mid-19th century, a dark-colored form appeared. The difference is produced by a dominant allele of one gene. By about 1900, approximately 90% of the moths around industrial areas were dark colored, whereas light-colored moths were still abundant elsewhere. Apparently, birds could readily find the light moths against the soot-darkened background in industrial areas and, therefore, were eating more light moths. Recently, use of cleaner fuels has greatly reduced soot in the landscape, and the dark-colored moths have been disappearing. Should the two forms of moths be considered separate species?

1. A) Yes; natural selection has affected the frequency of the two different forms.
2. B) Yes; they have completely different coloration.
3. C) Yes; they are reproductively isolated based on habitat.
4. D) No; they still can interbreed.

7) Which statement describes unity within a species?

1. A) A species can be distinguished by body shape and other structural features.
2. B) Members have the potential to interbreed in nature and produce viable, fertile offspring.
3. C) A species is described in terms of its interaction with living and non-living environment.
4. D) The DNA sequence lacks similarities.

8) The common edible frog of Europe is a hybrid between two 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 are rarely successful in producing offspring. What can you infer from this information?

1. A) Postzygotic isolation exists between the two frog species.
2. B) Prezygotic isolation exists between the two frog species.
3. C) These two species are likely in the process of fusing back into one species.
4. D) The hybrids form a separate species under the biological species concept.

9) Macroevolution is ________.

1. A) the same as microevolution, but includes the origin of new species
2. B) evolution above the species level
3. C) defined as the evolution of microscopic organisms into organisms that can be seen with the naked eye
4. D) defined as a change in allele or gene frequency over the course of many generations

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

1. A) genetic
2. B) ecological
3. C) biological
4. D) morphological

11) There is still some controversy among biologists about whether Neanderthals should be placed within the same species as modern humans or into a separate species of their own. Most DNA sequence data analyzed so far indicate that there was probably little or no gene flow between Neanderthals and Homo sapiens. Which species concept describing species relationship between modern humans and Neanderthals is most applicable in these observations?

1. A) genetic
2. B) ecological
3. C) morphological
4. D) biological

12) You are confronted with a box of preserved grasshoppers of various species that are new to science and have not been described. Your assignment is to separate them into species. There is no accompanying information as to where or when they were collected. Which species concept will you have to use?

1. A) biological
2. B) genetic
3. C) ecological
4. D) morphological

13) Dog breeders maintain the purity of breeds by keeping dogs of different breeds apart when they are fertile. This kind of isolation is most similar to which of the following reproductive isolating mechanisms?

1. A) temporal isolation
2. B) behavioral isolation
3. C) habitat isolation
4. D) gametic isolation

14) Rank the following in order from most general to most specific.

1. gametic isolation
2. reproductive isolating mechanism
3. sperm-egg incompatibility in sea urchins
4. prezygotic isolating mechanism
5. A) 2, 3, 1, 4
6. B) 2, 4, 1, 3
7. C) 4, 1, 2, 3
8. D) 4, 2, 1, 3

15) Two species of frogs belonging to the same genus occasionally mate, but the embryos stop developing after a day and then die. These two frog species separate by ________.

1. A) reduced hybrid viability
2. B) hybrid breakdown
3. C) reduced hybrid fertility
4. D) gametic isolation

16) The production of sterile mules by interbreeding between female horses (mares) and male donkeys (jacks) is an example of ________.

1. A) reduced hybrid viability
2. B) hybrid breakdown
3. C) reduced hybrid fertility
4. D) mechanical isolation

17) Which postzygotic barriers prevent formation of hybrids beyond the first generations?

1. A) increased hybrid vulnerability
2. B) increased hybrid fertility
3. C) hybrid breakdown
4. D) hybrid gamete isolation

18) Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. Pollen grains (which contain sperm cells) from one species are unable to germinate and make pollen tubes on female ovules (which contain egg cells) of the other species. These two juniper species are kept separate by ________.

1. A) habitat isolation
2. B) temporal isolation
3. C) gametic isolation
4. D) behavioral isolation

19) What does the biological species concept use as the primary criterion for determining species boundaries?

1. A) geographic isolation
2. B) niche differences
3. C) gene flow
4. D) morphological similarity

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

1. A) a population
2. B) a species
3. C) the entire range of a genus
4. D) the hybrid zone

21) Use the following information to answer the question.

About 3 million years ago, the Isthmus of Panama (a narrow strip of land connecting North and South America) formed, dividing marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sides of the isthmus. Based on the morphological species concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus, were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. (Reference: Y. Kondo and A. Kashiwagi. 2004. Experimentally induced autotetraploidy and allotetraploidy in two Japanese pond frogs. Journal of Herpetology 38(3):381-92.)

If the isthmus formed gradually rather than suddenly, what pattern of genetic divergence would you expect to find in these species pairs?

1. A) similar percentages of difference in DNA sequence between all pairs of sister species
2. B) greater percentage of difference in DNA sequence between species that inhabit deep water than between species that inhabit shallow water
3. C) greater percentage of difference in DNA sequence between species that inhabit shallow water than between species that inhabit deep water
4. D) smaller percentage of difference DNA sequence between species that inhabit than between shallow water

22) Which of the following describes the most likely order of events in allopatric speciation?

1. A) genetic drift, genetic isolation, divergence
2. B) genetic isolation, divergence, genetic drift
3. C) divergence, genetic drift, genetic isolation
4. D) genetic isolation, genetic drift, divergence

23) You want to study divergence of populations, and you need to maximize the rate of divergence to see results within the period of your grant funding. You will form a new population by taking some individuals from a source population and isolating them so the two populations cannot interbreed. What combination of characteristics would maximize your chance of seeing divergence in this study?

1. Choose a random sample of individuals to form the new population.
2. Choose individuals from one extreme to form the new population.
3. Choose a species to study that produces many offspring.
4. Choose a species to study that produces a few, large offspring.
5. Place the new population in the same type of environment as the source population.
6. Place the new population in a novel environment compared to that of the source population.
7. A) 1, 3, and 6
8. B) 1, 4, and 6
9. C) 2, 3, and 5
10. D) 2, 3, and 6

24) Which of these animals could overcome the geographic barrier of water that causes allopatric speciation?

1. A) birds
2. B) pollen
3. C) small rodents
4. D) mountain lions

25) How are two different species most likely to evolve from one ancestral species?

1. A) sympatrically, by a point mutation affecting morphology or behavior
2. B) sympatrically, due to extensive inbreeding
3. C) allopatrically, due to extensive inbreeding
4. D) allopatrically, after the ancestral species has split into two populations

26) House finches were found only in western North America until 1939, when a few individuals were released in New York City. These individuals established a breeding population and gradually expanded their range. The western population also expanded its range somewhat eastward, and the two populations have recently come in contact. If the two forms were unable to interbreed when their expanding ranges met, it would be an example of ________.

1. A) prezygotic isolation
2. B) reinforcement
3. C) allopatric speciation
4. D) sympatric speciation

27) Most causes of speciation are relatively slow in that they may take many generations to see changes, with the exception of ________.

1. A) polyploidy
2. B) reinforcement
3. C) colonization
4. D) natural selection

28) Two researchers experimentally formed tetraploid frogs by fertilizing diploid eggs from Rana porosa brevipoda with diploid sperm from Rana nigromaculata. When they mated these tetraploid frogs with each other, most of the offspring that survived to maturity were tetraploid, with chromosome sets of both diploid parent species. Based on these results, if this type of tetraploid formed in the wild, what would be the result? (Reference: Y. Kondo and A. Kashiwagi. 2004. Experimentally induced autotetraploidy and allotetraploidy in two Japanese pond frogs. Journal of Herpetology 38(3):381−92.)

1. A) The two parent species would interbreed and fuse into one species.
2. B) The two parent species would recognize each other as mates.
3. C) The tetraploids would be reproductively isolated from both parent species.
4. D) The tetraploids would be selected against.

29) How can reproductive barriers form sympatric populations while their members remain in the same geographic area?

1. A) increased gene flow
2. B) polyploidy
3. C) decreased sexual selection
4. D) habitat sharing

30) Two species of tree frogs that live sympatrically in the northeastern United States differ in ploidy: Hyla chrysoscelis is diploid, and Hyla versicolor is tetraploid. The frogs are identical in appearance, but their mating calls, which females use to find mates, differ. Which difference most likely evolved first?

1. A) polyploidy
2. B) difference in mating calls
3. C) habitat differentiation
4. D) Polyploidy and different mating calls must have evolved at the same time.

31) In a hypothetical situation, a certain species of flea feeds only on pronghorn antelopes. In the western United States, pronghorns and cattle often associate with one another in the same open rangeland. Some of these fleas develop a strong preference for cattle blood and mate only with other fleas that prefer cattle blood. The host mammal can be considered as the fleas' habitat. If this situation persists, and new species evolve, this would be an example of ________.

1. A) sympatric speciation and habitat isolation
2. B) sympatric speciation and temporal isolation
3. C) allopatric speciation and habitat isolation
4. D) allopatric speciation and gametic isolation

32) The difference between geographic isolation and habitat differentiation (isolation) is the ________.

1. A) relative location of two populations as speciation occurs
2. B) speed (tempo) at which two populations undergo speciation
3. C) amount of genetic variation that occurs among two gene pools as speciation occurs
4. D) identity of the kingdom or domain in which these phenomena occur

33) Among known plant species, which of these have been the two most commonly occurring phenomena that have led to the origin of new species?

1. A) allopatric speciation and sexual selection
2. B) allopatric speciation and polyploidy
3. C) sympatric speciation and sexual selection
4. D) sympatric speciation and polyploidy

34) Beetle pollinators of a particular plant are attracted to its flowers' bright orange color. The beetles not only pollinate the flowers, but they mate while inside of the flowers. A mutant version of the plant with red flowers becomes more common with the passage of time. A particular variant of the beetle prefers the red flowers to the orange flowers. Over time, these two beetle variants diverge from each other to such an extent that interbreeding is no longer possible. What kind of speciation has occurred in this example, and what has driven it?

1. A) allopatric speciation; ecological isolation
2. B) sympatric speciation; habitat differentiation
3. C) allopatric speciation; behavioral isolation
4. D) sympatric speciation; allopolyploidy

35) Use the following description to answer the question.

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila yakuba inhabits the island's lowlands and is also found on the African mainland, located about two hundred miles away. At higher elevations, and only on Sao Tomé, is found the very closely related Drosophila santomea. The two species can hybridize, though male hybrids are sterile. A hybrid zone exists at middle elevations, though hybrids there are greatly outnumbered by D. santomea. Studies of the two species' nuclear genomes reveal that D. yakuba on the island is more closely related to mainland D. yakuba than to D. santomea (2n = 4 in both species). Sao Tomé rose from the Atlantic Ocean about 14 million years ago.

Using only the information provided in the paragraph, which of the following is the best initial hypothesis for how D. santomea descended from D. yakuba?

1. A) allopolyploidy
2. B) autopolyploidy
3. C) habitat differentiation
4. D) sexual selection

36) Use the following description to answer the question.

On the Bahamian island of Andros, mosquitofish populations live in various, now-isolated freshwater ponds that were once united. Currently, some predator-rich ponds have mosquitofish that can swim in short, fast bursts; other predator-poor ponds have mosquitofish that can swim continuously for a long time. When placed together in the same body of water, the two kinds of female mosquitofish exhibit exclusive breeding preferences.

Which two of the following have operated to increase divergence between mosquitofish populations on Andros?

1. improved gene flow
2. bottleneck effect
3. sexual selection
4. founder effect
5. natural selection
6. A) 1 and 3
7. B) 2 and 3
8. C) 2 and 4
9. D) 3 and 5

37) Use the following description to answer the question.

In the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. The oceans were completely separated by the isthmus about 3 million years ago.

In the figure, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1-5), with 1 being the shallowest.

Why should deepwater shrimp on different sides of the isthmus have diverged from each other earlier than shallow-water shrimp?

1. A) They have been geographically isolated from each other for a longer time.
2. B) Cold temperatures, associated with deep water, have accelerated the mutation rate, resulting in faster divergence in deepwater shrimp.
3. C) The rise of the land bridge was accompanied by much volcanic activity. Volcanic ash contains heavy metals, which are known mutagens. Ash fall caused high levels of heavy metals in the ocean sediments underlying the deep water, resulting in accelerated mutation rates and faster divergence in deepwater shrimp.
4. D) Fresh water entering the ocean from the canal is both less dense and cloudier than seawater. The cloudy fresh water interferes with the ability of shallow-water shrimp to locate mating partners, which reduces the frequency of mating, thereby slowing the introduction of genetic variation.

38) Use the following description to answer the question.

In the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. The oceans were completely separated by the isthmus about 3 million years ago.

In the figure, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1-5), with 1 being the shallowest.

In which habitat should one find snapping shrimp most closely related to shrimp that live in habitat A4?

1. A) A3
2. B) A5
3. C) B4
4. D) either A3 or A5

39) Use the following description to answer the question.

In the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. The oceans were completely separated by the isthmus about 3 million years ago.

In the figure, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1-5), with 1 being the shallowest.

Which of these habitats is likely to harbor the most recently diverged species?

1. A) A5
2. B) B4
3. C) A3
4. D) A1

40) Use the following description to answer the question.

In the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. The oceans were completely separated by the isthmus about 3 million years ago.

In the figure, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1-5), with 1 being the shallowest.

Which habitats should harbor snapping shrimp species with the greatest degree of genetic divergence from each other?

1. A) A1 and A5
2. B) A1 and B5
3. C) A5 and B5
4. D) Both A1/A5 and B1/B5 should have the greatest, but equal amounts of, genetic divergence

41) Use the following description to answer the question.

In the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. The oceans were completely separated by the isthmus about 3 million years ago.

In the figure, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1-5), with 1 being the shallowest.

Which factor is most important for explaining why there are equal numbers of snapping shrimp species on either side of the isthmus?

1. A) the relative shortness of time they have been separated
2. B) the depth of the sea
3. C) the number of actual depth habitats between the surface and the sea floor
4. D) the elevation of the isthmus above sea level

42) Use the following description to answer the question.

In the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. The oceans were completely separated by the isthmus about 3 million years ago.

In the figure, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1-5), with 1 being the shallowest.

The Panama Canal was completed in 1914, and its depth is about 50 feet. After 1914, snapping shrimp species from which habitats should be most likely to form hybrids as the result of the canal?

1. A) A5 and B5
2. B) A3 and B3
3. C) A1 and B1
4. D) A1-A3 and B1-B3 have equal likelihoods of harboring snapping shrimp species that can

43) Plant species A has a diploid 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 ________.

1. A) 14
2. B) 16
3. C) 28
4. D) 56

44) A small number of birds arrive on an island from a neighboring larger island. This small population begins to adapt to the new food plants available on the island, and their beaks begin to change. About twice a year, one or two more birds from the neighboring island arrive. These new arrivals ________.

1. A) speed up the process of speciation
2. B) tend to promote adaptation to the new food plants
3. C) tend to slow adaptation to the new food plants
4. D) represent a colonizing event response

45) How do hybrid zones slow reproductive isolation?

1. A) species with incomplete mating barriers
2. B) decreased embryonic mortality
3. C) increased gene flow
4. D) morphologic abnormalities

46) What happens to the hybrid zone when gene flow is established?

1. A) A population merges with another population.
2. B) Hybrids cease to be formed.
3. C) weakening of reproductive barriers
4. D) continued production of hybrids

47) Reinforcement is most likely to occur when ________.

1. A) the environment is changing
2. B) hybrids have lower fitness than either parent population
3. C) prezygotic isolating mechanisms are in place
4. D) gene flow is low

48) The phenomenon of fusion is likely to occur when, after a period of geographic isolation, two populations meet again and ________.

1. A) an increasing number of infertile hybrids is produced over the course of the next 100 generations
2. B) no reproduction occurs in the hybrid zone
3. C) an increasing number of viable, fertile hybrids is produced over the course of the next 100 generations
4. D) a decreasing number of viable, fertile hybrids is produced over the course of the next 100 generations

49) A hybrid zone is properly defined as ________.

1. A) an area where the ranges of two closely related species overlap but do not interbreed
2. B) an area where mating occurs between members of two closely related species, producing viable offspring
3. C) a zone where sterile hybrids form, kept separate by postzygotic barriers
4. D) an area where members of two closely related species intermingle, but gene flow is prevented by prezygotic barriers

50) In hybrid zones where reinforcement is occurring, we should see a decline in ________.

1. A) gene flow between distinct gene pools
2. B) speciation
3. C) the genetic distinctness of two gene pools
4. D) mutation rates

51) Other than predation by introduced Nile perch, the most likely explanation for the recent decline in cichlid species diversity in Lake Victoria is ________.

1. A) reinforcement
2. B) fusion
3. C) stability
4. D) polyploidy

52) A narrow hybrid zone separates the toad species Bombina bombina and Bombina variegata. What is true of those alleles that are unique to the parental species?

1. A) Such alleles should be absent.
2. B) Their allele frequency should be nearly the same as the allele frequencies in toad populations distant from the hybrid zone.
3. C) The alleles heterozygosity should be higher among the hybrid toads than in toad populations distant from the hybrid zone.
4. D) Their allele frequency on one edge of the hybrid zone should roughly equal their frequency on the opposite edge of the hybrid zone.

53) Use the following description to answer the question.

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila yakuba inhabits the island's lowlands and is also found on the African mainland, located about two hundred miles away. At higher elevations, and only on Sao Tomé, is found the very closely related Drosophila santomea. The two species can hybridize, though male hybrids are sterile. A hybrid zone exists at middle elevations, though hybrids there are greatly outnumbered by D. santomea. Studies of the two species' nuclear genomes reveal that D. yakuba on the island is more closely related to mainland D. yakuba than to D. santomea (2n = 4 in both species). Sao Tomé rose from the Atlantic Ocean about 14 million years ago.

The observation that island D. yakuba are more closely related to mainland D. yakuba than island D. yakuba are to D. santomea is best explained by proposing that D. santomea ________.

1. A) descended from a now-extinct, non-African fruit fly
2. B) arrived on the island before D. yakuba
3. C) descended from a single colony of D. yakuba, which had been introduced from elsewhere, with no subsequent colonization events
4. D) descended from an original colony of D. yakuba, of which there are no surviving members. The current island D. yakuba represent a second colonization event from elsewhere

54) Use the following description to answer the question.

On the Bahamian island of Andros, mosquitofish populations live in various, now-isolated freshwater ponds that were once united. Currently, some predator-rich ponds have mosquitofish that can swim in short, fast bursts; other predator-poor ponds have mosquitofish that can swim continuously for a long time. When placed together in the same body of water, the two kinds of female mosquitofish exhibit exclusive breeding preferences.

What is the best way to promote fusion between two related populations of mosquitofish, one of which lives in a predator-rich pond and the other of which lives in a predator-poor pond?

1. A) Build a canal linking the two ponds that permits free movement of mosquitofish, but not of predators.
2. B) Transfer only female mosquitofish from a predator-rich pond to a predator-poor pond.
3. C) Perform a reciprocal transfer of females between predator-rich and predator-poor ponds.
4. D) Remove predators from a predator-rich pond and transfer them to a predator-poor pond.

55) Suppose that a group of male pied flycatchers migrated from a region where there were no collared flycatchers to a region where both species were present. Assuming events like this are very rare, which of the following scenarios is least likely?

1. A) Migrant pied males would produce fewer offspring than would resident pied males.
2. B) Pied females would rarely mate with collared males.
3. C) Migrant males would mate with collared females more often than with pied females.
4. D) The frequency of hybrid offspring would decrease.

56) The following question refers to this hypothetical situation.

A female fly, full of fertilized eggs, is swept by high winds to an island far out to sea. She is the first fly to arrive on this island and the only fly to arrive in this way. Thousands of years later, her numerous offspring occupy the island, but none of them resembles her. There are, instead, several species, each of which eats only a certain type of food. None of the species can fly and their balancing organs (halteres) are now used in courtship displays. The male members of each species bear modified halteres that are unique in appearance to their species. Females bear vestigial halteres. The ranges of all of the daughter species overlap.

Fly species W, found in a certain part of the island, produces fertile offspring with species Y. Species W does not produce fertile offspring with species X or Z. If no other species can hybridize, then which of the following statements about species W and Y are true?

1. I) Species W and Y have genomes that are still similar enough for successful meiosis to occur in hybrid flies.
2. II) Species W and Y have more genetic similarity with each other than either did with the other two species.

III) Species W and Y may fuse into a single species if their hybrids remain fertile over the course of many generations.

1. A) Only I is correct.
2. B) Only II is correct.
3. C) Only III is correct.
4. D) I, II, and III are correct.

57) According to the concept of punctuated equilibrium, the "sudden" appearance of a new species in the fossil record means that ________.

1. A) the species is now extinct
2. B) speciation occurred in one generation
3. C) speciation occurred rapidly in geologic time
4. D) the species will consequently have a relatively short existence compared with other species

58) How is length of time for speciation estimated?

1. A) genetic evidence indicates that species originate
2. B) time that elapses when populations of a newly formed species diverge
3. C) time it takes for speciation to be complete
4. D) speciation precedes divergence

59) Speciation ________.

1. A) occurs at such a slow pace that no one has ever observed the emergence of new species
2. B) occurs only by the accumulation of small genetic changes over vast expanses of time
3. C) must begin with the geographic isolation of a small, frontier population
4. D) can involve changes to a single gene

60) According to the biological species concept, for speciation to occur, ________.

1. A) the number of chromosomes in the gene pool must change
2. B) changes to centromere location or chromosome size must occur
3. C) large numbers of genes that affect numerous phenotypic traits must change
4. D) at least one gene, affecting one reproductive barrier, must change

61) The question refers to the following evolutionary tree, in which the horizontal axis represents time (present time is on the far right), and the vertical axis represents morphological change.

Which conclusion can be drawn from this evolutionary tree?

1. A) A single clade (that is, a group of species that share a common ancestor) can include species that formed by gradualism and other species that formed by punctuated equilibrium.
2. B) A single clade (that is, a group of species that share a common ancestor) will either include species that formed by gradualism or species that formed by punctuated equilibrium.
3. C) Assuming that the tip of each line represents a species, there are five extant (that is, not extinct) species resulting from the earliest common ancestor.
4. D) Species X and Z best represent species that evolved by punctuated equilibrium.