Deck 24: The Origin of Species

Question 1

The questions below are based on the following description.
Several closely related frog species of the genus Rana are found in the forests of the southeastern United States. The species boundaries are maintained by reproductive barriers. In each case, match the various descriptions of frogs below with the appropriate reproductive barrier listed.
Females of one species choose mates based on song quality; females of another species choose mates on the basis of size.

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

Answer 1

A

Question 2

A biologist discovers two populations of wolf spiders whose members appear identical. Members of one population are found in the leaf litter deep within the woods. Members of the other population are found in the grass at the edge of the woods. The biologist decides to designate the members of the two populations as two separate species. Which species concept is this biologist most closely utilizing?

A)ecological
B)biological
C)morphological
D)phylogenetic

Answer 2

A

Question 3

Rank the following from most general to most specific: 1. gametic isolation
2) reproductive isolating mechanism
3) pollen-stigma incompatibility
4) prezygotic isolating mechanism

A)2, 3, 1, 4
B)2, 4, 1, 3
C)4, 1, 2, 3
D)4, 2, 1, 3
E)2, 1, 4, 3

Answer 3

B

Question 4

Two species of frogs belonging to the same genus occasionally mate, but the offspring fail to develop and hatch. What is the mechanism for keeping the two frog species separate?

A)the postzygotic barrier called hybrid inviability
B)the postzygotic barrier called hybrid breakdown
C)the prezygotic barrier called hybrid sterility
D)gametic isolation
E)adaptation

Question 5

The questions below are based on the following description.
Several closely related frog species of the genus Rana are found in the forests of the southeastern United States. The species boundaries are maintained by reproductive barriers. In each case, match the various descriptions of frogs below with the appropriate reproductive barrier listed.
Males of one species sing only when its predators are absent; males of another species sing only when its predators are present.

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

Question 6

What was the species concept most used by Linnaeus?

A)biological
B)morphological
C)ecological
D)phylogenetic

Question 7

Which species concept is currently most popular among most biologists?

A)phylogenetic
B)ecological
C)biological
D)morphological

Question 8

Theoretically, the production of sterile mules by interbreeding between female horses and male donkeys should

A)result in the extinction of one of the two parental species.
B)cause convergent evolution.
C)strengthen postzygotic barriers between horses and donkeys.
D)weaken the intrinsic reproductive barriers between horses and donkeys.
E)eventually result in the formation of a single species from the two parental species.

Question 9

Which of the following statements about species, as defined by the biological species concept, is (are)correct?
I) Biological species are defined by reproductive isolation.
II) Biological species are the model used for grouping extinct forms of life.
III) The biological species is the largest unit of population in which successful reproduction is possible.

A)I only
B)II only
C)I and III
D)II and III
E)I, II, and III

Question 10

The questions below are based on the following description.
Several closely related frog species of the genus Rana are found in the forests of the southeastern United States. The species boundaries are maintained by reproductive barriers. In each case, match the various descriptions of frogs below with the appropriate reproductive barrier listed.
One species mates at the season when daylight is increasing from 13 hours to 13 hours, 15 minutes; another species mates at the season when daylight is increasing from 14 hours to 14 hours, 15 minutes.

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

Question 11

The questions below are based on the following description.
Several closely related frog species of the genus Rana are found in the forests of the southeastern United States. The species boundaries are maintained by reproductive barriers. In each case, match the various descriptions of frogs below with the appropriate reproductive barrier listed.
One species lives only in tree holes; another species lives only in streams.

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

Question 12

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

A)phylogenetic
B)ecological
C)biological
D)morphological

Question 13

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?

A)biological
B)phylogenetic
C)ecological
D)morphological

Question 14

The questions below are based on the following description.
Several closely related frog species of the genus Rana are found in the forests of the southeastern United States. The species boundaries are maintained by reproductive barriers. In each case, match the various descriptions of frogs below with the appropriate reproductive barrier listed.
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?

A)reduced hybrid fertility
B)hybrid breakdown
C)mechanical isolation
D)habitat isolation
E)gametic isolation

Question 15

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 is most applicable in this example?

A)phylogenetic
B)ecological
C)morphological
D)biological

Question 16

The questions below are based on the following description.
Several closely related frog species of the genus Rana are found in the forests of the southeastern United States. The species boundaries are maintained by reproductive barriers. In each case, match the various descriptions of frogs below with the appropriate reproductive barrier listed.
Males of one species are too small to perform amplexus (an action that stimulates ovulation)with females of all other species.

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

Question 17

Races of humans are unlikely to evolve extensive differences in the future for which of the following reasons?
I) The environment is unlikely to change.
II) Human evolution is complete.
III) The human races are incompletely isolated.

A)I only
B)III only
C)I and II only
D)II and III only
E)I, II, and III

Question 18

The biological species concept is inadequate for grouping

A)plants.
B)parasites.
C)asexual organisms.
D)animals that migrate.
E)sympatric populations.

Question 19

Which example below will most likely guarantee that two closely related species will persist only as distinct biological species?

A)colonization of new habitats
B)convergent evolution
C)hybridization
D)geographic isolation from one another
E)reproductive isolation from one another

Question 20

What is generally True of two very closely related species that have diverged from each other quite recently?

A)They shared a common ancestor recently in evolutionary time.
B)Genes are unable to pass from one species' gene pool to the other's gene pool.
C)They are unable to produce hybrid offspring upon interbreeding.
D)Their reproductive isolation from each other is complete.

Question 21

The following questions refer to the description below.
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 200 miles away. At higher elevations, and found 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.
Which of these reduces gene flow between the gene pools of the two species on Sao Tomé, despite the existence of hybrids?

A)hybrid breakdown
B)hybrid inviability
C)hybrid sterility
D)temporal isolation
E)a geographic barrier

Question 22

The following questions refer to the description below.
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 200 miles away. At higher elevations, and found 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 these is the best initial hypothesis for how D. santomea descended from D. yakuba?

A)geographic isolation
B)autopolyploidy
C)habitat differentiation
D)sexual selection
E)allopolyploidy

Question 23

A rapid method of speciation that has been important in the history of flowering plants is

A)genetic drift.
B)a mutation in the gene controlling the timing of flowering.
C)behavioral isolation.
D)polyploidy.

Question 24

The most likely explanation for the high rate of sympatric speciation that apparently existed among the cichlids of Lake Victoria in the past is

A)sexual selection.
B)habitat differentiation.
C)polyploidy.
D)pollution.
E)introduction of a new predator.

Question 25

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

A)their chromosomes are no longer homologous enough to permit meiosis.
B)a constant number of viable, fertile hybrids is produced over the course of generations.
C)the hybrid zone is inhospitable to hybrid survival.
D)an increasing number of viable, fertile hybrids is produced over the course of generations
E)a decreasing number of viable, fertile hybrids is produced over the course of generations.

Question 26

The following questions refer to the description below.
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 200 miles away. At higher elevations, and found 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.
If a speciation event occurred on Sao Tomé, producing D. santomea from a parent colony of D. yakuba, then which terms apply?
I) macroevolution
II) allopatric speciation
III) sympatric speciation

A)I only
B)II only
C)I & II
D)I & III

Question 27

The constantly changing nature of the Appalachian ground crickets (Allonemobius fasciatus and Allonemobius socius)hybrid zone favors

A)no gene flow between the two gene pools.
B)little gene flow between the two gene pools.
C)increased levels of gene flow between the two gene pools.
D)extinction of both species as the hybrids persist.

Question 28

Which of these should decline in hybrid zones where reinforcement is occurring?

A)gene flow between distinct gene pools
B)speciation
C)the genetic distinctness of two gene pools
D)mutation rate
E)hybrid sterility

Question 29

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?

A)allopatric speciation, ecological isolation
B)sympatric speciation, habitat differentiation
C)allopatric speciation, behavioral isolation
D)sympatric speciation, sexual selection
E)sympatric speciation, allopolyploidy

Question 30

In a hypothetical situation, a certain species of flea feeds only on pronghorn antelopes. In rangelands of the western United States, pronghorns and cattle often associate with one another. If some of these fleas develop a strong preference, instead, for cattle blood and mate only with fleas that, likewise, prefer cattle blood, then over time which of these should occur, if the host mammal can be considered as the fleas' habitat?
1) reproductive isolation
2) sympatric speciation
3) habitat isolation
4) prezygotic barriers

A)1 only
B)2 and 3
C)1, 2, and 3
D)2, 3, and 4
E)1 through 4

Question 31

The origin of a new plant species by hybridization, coupled with accidents during nuclear division, is an example of

A)allopatric speciation.
B)sympatric speciation.
C)autopolyploidy.
D)habitat selection.

Question 32

A hybrid zone is properly defined as

A)an area where two closely related species' ranges overlap.
B)an area where mating occurs between members of two closely related species, producing viable offspring.
C)a zone that features a gradual change in species composition where two neighboring ecosystems border each other.
D)a zone that includes the intermediate portion of a cline.
E)an area where members of two closely related species intermingle, but experience no gene flow.

Question 33

Among known plant species, which of these have been the two most commonly occurring phenomena leading to the origin of new species?
1) allopatric speciation
2) sympatric speciation
3) sexual selection
4) polyploidy

A)1 and 3
B)1 and 4
C)2 and 3
D)2 and 4

Question 34

The most likely explanation for the recent decline in cichlid species diversity in Lake Victoria is

A)reinforcement.
B)fusion.
C)stability.
D)geographic isolation.
E)polyploidy.

Question 35

The difference between geographic isolation and habitat differentiation is the

A)relative locations of two populations as speciation occurs.
B)speed (tempo)at which two populations undergo speciation.
C)amount of genetic variation that occurs among two gene pools as speciation occurs.
D)identity of the phylogenetic kingdom or domain in which these phenomena occur.
E)the ploidy of the two populations as speciation occurs.

Question 36

Two closely related populations of mice have been separated for many generations by a river. Climatic change causes the river to dry up, thereby bringing the mice populations back into contact in a zone of overlap. Which of the following is not a possible outcome when they meet?

A)They interbreed freely and produce fertile hybrid offspring.
B)They no longer attempt to interbreed.
C)They interbreed in the region of overlap, producing an inferior hybrid. Subsequent interbreeding between inferior hybrids produces progressively superior hybrids over several generations.
D)They remain separate in the extremes of their ranges but develop a persistent hybrid zone in the area of overlap.
E)They interbreed in the region of overlap, but produce sterile offspring.

Question 37

The following questions refer to the description below.
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 200 miles away. At higher elevations, and found 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.
Which of these evolutionary trees represents the situation described in the paragraph above (NOTE: yakuba (I)represents the island population, and yakuba (M)represents the mainland population)?

A)
B)
C)
D)

Question 38

A defining characteristic of allopatric speciation is

A)the appearance of new species in the midst of old ones.
B)asexually reproducing populations.
C)geographic isolation.
D)artificial selection.
E)large populations.

Question 39

In the narrow hybrid zone that separates the toad species Bombina bombina and Bombina variegata, what is True of those alleles that are unique to the parental species?

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

Question 40

The following questions refer to the description below.
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 200 miles away. At higher elevations, and found 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

A)descended from a now-extinct, non-African fruit fly.
B)arose de novo; that is, had no ancestors.
C)descended from a single colony of D. yakuba, which had been introduced from elsewhere, with no subsequent colonization events.
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.

Question 41

The following questions refer to the evolutionary tree below, whose horizontal axis represents time (present time is on the far right) and whose vertical axis represents morphological change.
Figure 24.1
Which of these five species is the extant (i.e., not extinct)species that is most closely related to species X, and why is this so?

A)V; shared a common ancestor with X most recently
B)W; shared a common ancestor with X most recently
C)Y; arose in the same fashion (i.e., at the same tempo)as X
D)Z; shared a common ancestor with X most recently, and arose in the same fashion as X
E)This tree does not provide enough information to answer this question.

Question 42

Males of different species of the fruit fly Drosophila that live in the same parts of the Hawaiian islands have different elaborate courtship rituals that involve fighting other males and stylized movements that attract females. What type of reproductive isolation does this represent?

A)habitat isolation
B)temporal isolation
C)behavioral isolation
D)gametic isolation
E)postzygotic barriers

Question 43

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

A)population.
B)species.
C)genus.
D)hybrid.
E)phylum.

Question 44

The following questions refer to the paragraph and graphs below.
In a hypothetical situation, the National Park Service, which administers Grand Canyon National Park in Arizona, builds a footbridge over the Colorado River at the bottom of the canyon. The footbridge permits interspersal of two closely related antelope squirrels. Previously, one type of squirrel had been restricted to the terrain south of the river, and the other type had been restricted to terrain on the north side of the river. Immediately before and ten years after the bridge's completion, ten antelope squirrels from both sides of the river were collected, blood samples were taken, and frequencies of alleles unique to the two types of antelope squirrels were determined (see graphs below).


Which of the following statements about speciation is correct?

A)The goal of natural selection is speciation.
B)When reunited, two allopatric populations will not interbreed.
C)Natural selection chooses the reproductive barriers for populations.
D)Prezygotic reproductive barriers usually evolve before postzygotic barriers.
E)Speciation is a basis for understanding macroevolution.

Question 45

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?

A)The two forms interbreed often in nature, and their offspring have good survival and reproduction.
B)The two forms live in similar habitats.
C)The two forms have many genes in common.
D)The two forms have similar food requirements.
E)The two forms are very similar in coloration.

Question 46

The following questions refer to the evolutionary tree below, whose horizontal axis represents time (present time is on the far right) and whose vertical axis represents morphological change.
Figure 24.1
Which of these five species originated earliest and appeared suddenly in the fossil record?

A)V
B)W
C)X
D)Y
E)Z

Question 47

The following questions refer to the paragraph and graphs below.
In a hypothetical situation, the National Park Service, which administers Grand Canyon National Park in Arizona, builds a footbridge over the Colorado River at the bottom of the canyon. The footbridge permits interspersal of two closely related antelope squirrels. Previously, one type of squirrel had been restricted to the terrain south of the river, and the other type had been restricted to terrain on the north side of the river. Immediately before and ten years after the bridge's completion, ten antelope squirrels from both sides of the river were collected, blood samples were taken, and frequencies of alleles unique to the two types of antelope squirrels were determined (see graphs below).


According to the concept of punctuated equilibrium,

A)natural selection is unimportant as a mechanism of evolution.
B)given enough time, most existing species will branch gradually into new species.
C)a new species accumulates most of its unique features as it comes into existence.
D)evolution of new species features long periods during which changes are occurring, interspersed with short periods of equilibrium, or stasis.
E)transitional fossils, intermediate between newer species and their parent species, should be abundant.

Question 48

The following questions refer to the paragraph and graphs below.
In a hypothetical situation, the National Park Service, which administers Grand Canyon National Park in Arizona, builds a footbridge over the Colorado River at the bottom of the canyon. The footbridge permits interspersal of two closely related antelope squirrels. Previously, one type of squirrel had been restricted to the terrain south of the river, and the other type had been restricted to terrain on the north side of the river. Immediately before and ten years after the bridge's completion, ten antelope squirrels from both sides of the river were collected, blood samples were taken, and frequencies of alleles unique to the two types of antelope squirrels were determined (see graphs below).


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

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

Question 49

The following questions refer to the paragraph and graphs below.
In a hypothetical situation, the National Park Service, which administers Grand Canyon National Park in Arizona, builds a footbridge over the Colorado River at the bottom of the canyon. The footbridge permits interspersal of two closely related antelope squirrels. Previously, one type of squirrel had been restricted to the terrain south of the river, and the other type had been restricted to terrain on the north side of the river. Immediately before and ten years after the bridge's completion, ten antelope squirrels from both sides of the river were collected, blood samples were taken, and frequencies of alleles unique to the two types of antelope squirrels were determined (see graphs below).


In order for speciation to occur, what is True?

A)The number of chromosomes in the genome must change.
B)Changes to centromere location or chromosome size must occur within the genome.
C)Large numbers of genes that affect a single phenotypic trait must change.
D)Large numbers of genes that affect numerous phenotypic traits must change.
E)At least one gene, affecting at least one phenotypic trait, must change.

Question 50

The following questions refer to the paragraph and graphs below.
In a hypothetical situation, the National Park Service, which administers Grand Canyon National Park in Arizona, builds a footbridge over the Colorado River at the bottom of the canyon. The footbridge permits interspersal of two closely related antelope squirrels. Previously, one type of squirrel had been restricted to the terrain south of the river, and the other type had been restricted to terrain on the north side of the river. Immediately before and ten years after the bridge's completion, ten antelope squirrels from both sides of the river were collected, blood samples were taken, and frequencies of alleles unique to the two types of antelope squirrels were determined (see graphs below).


The results depicted in the graphs above are best accounted for by which of the following facts?

A)The Colorado River has been an effective geographic barrier to these two types of squirrels for several million years.
B)There is more white fur on the tails of the northern squirrels than on the tails of the southern squirrels.
C)Both types of squirrel subsist largely on a diet of pine nuts and juniper seeds in this ecosystem.
D)Both types of squirrel share the same common ancestor.
E)Both types of squirrel are active during the day.

Question 51

The following questions refer to the paragraph and graphs below.
In a hypothetical situation, the National Park Service, which administers Grand Canyon National Park in Arizona, builds a footbridge over the Colorado River at the bottom of the canyon. The footbridge permits interspersal of two closely related antelope squirrels. Previously, one type of squirrel had been restricted to the terrain south of the river, and the other type had been restricted to terrain on the north side of the river. Immediately before and ten years after the bridge's completion, ten antelope squirrels from both sides of the river were collected, blood samples were taken, and frequencies of alleles unique to the two types of antelope squirrels were determined (see graphs below).


Upon undergoing change, which of these genes is most likely to result in speciation while a geographic barrier separates two populations of a flowering-plant species?

A)one that affects the rate of chlorophyll a synthesis
B)one that affects the amount of growth hormone synthesized per unit time
C)one that affects the compatibility of male pollen and female reproductive parts
D)one that affects the average depth to which roots grow down through the soil
E)one that affects how flexible the stems are

Question 52

The following questions refer to the evolutionary tree below, whose horizontal axis represents time (present time is on the far right) and whose vertical axis represents morphological change.
Figure 24.1
Which conclusion can be drawn from this evolutionary tree?

A)Gradualistic speciation and speciation involving punctuated equilibrium are mutually exclusive concepts; only one of them can occur.
B)Eldredge and Gould would deny that the lineages labeled X, Y, and Z could represent True species.
C)Assuming that the tip of each line represents a species, there are five extant (i.e., not extinct)species resulting from the earliest common ancestor.
D)A single clade (i.e., a group of species that share a common ancestor)can exhibit both gradualism and punctuated equilibrium.
E)V and W shared a common ancestor more recently than any of the other species.

Question 53

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

A)A population becomes geographically isolated from the parent population.
B)The separated population is small, and genetic drift occurs.
C)The isolated population is exposed to different selection pressures than the ancestral population.
D)Different mutations begin to distinguish the gene pools of the separated populations.
E)Gene flow between the two populations is extensive.

Question 54

The following questions refer to the description below.
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 200 miles away. At higher elevations, and found 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.
If the low number of hybrid flies in the hybrid zone, relative to the number of D. santomea flies there, is due to the fact that hybrids are poorly adapted to conditions in the hybrid zone, and if fewer hybrid flies are produced with the passage of time, this is most likely to lead to

A)fusion.
B)reinforcement.
C)stability.
D)further speciation events.

Question 55

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

A)12.
B)14.
C)16.
D)28.
E)56.

Question 56

The following questions refer to the evolutionary tree below, whose horizontal axis represents time (present time is on the far right) and whose vertical axis represents morphological change.
Figure 24.1
Which of these five species (V-Z)in the evolutionary tree would likely have fossil records indicating that punctuated equilibrium was an important part of their evolutionary history?

A)V and W
B)V and Y
C)X and Y
D)W, Y, and Z
E)X, Y, and Z

Question 57

The following questions refer to the paragraph and graphs below.
In a hypothetical situation, the National Park Service, which administers Grand Canyon National Park in Arizona, builds a footbridge over the Colorado River at the bottom of the canyon. The footbridge permits interspersal of two closely related antelope squirrels. Previously, one type of squirrel had been restricted to the terrain south of the river, and the other type had been restricted to terrain on the north side of the river. Immediately before and ten years after the bridge's completion, ten antelope squirrels from both sides of the river were collected, blood samples were taken, and frequencies of alleles unique to the two types of antelope squirrels were determined (see graphs below).


The data in the graphs above indicate that

A)a hybrid zone was established after the completion of the bridge.
B)no interspersal of the two types of squirrel occurred after the completion of the bridge.
C)gene flow occurred from one type of squirrel into the gene pool of the other type of squirrel.
D)2-way migration of squirrels occurred across the bridge, but without hybridization.
E)some northern squirrels migrated south, but no southern squirrels migrated north across the bridge.

Question 58

The following questions refer to the paragraph and graphs below.
In a hypothetical situation, the National Park Service, which administers Grand Canyon National Park in Arizona, builds a footbridge over the Colorado River at the bottom of the canyon. The footbridge permits interspersal of two closely related antelope squirrels. Previously, one type of squirrel had been restricted to the terrain south of the river, and the other type had been restricted to terrain on the north side of the river. Immediately before and ten years after the bridge's completion, ten antelope squirrels from both sides of the river were collected, blood samples were taken, and frequencies of alleles unique to the two types of antelope squirrels were determined (see graphs below).


Speciation

A)occurs at such a slow pace that no one has ever observed the emergence of new species.
B)occurs only by the accumulation of genetic change over vast expanses of time.
C)must begin with the geographic isolation of a small, frontier population.
D)proceeds at a uniform tempo across all taxa.
E)can involve changes involving a single gene.

Question 59

According to the punctuated equilibria model,

A)natural selection is unimportant as a mechanism of evolution.
B)given enough time, most existing species will branch gradually into new species.
C)most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.
D)most evolution occurs in sympatric populations.
E)speciation is usually due to a single mutation.

Question 60

The following questions refer to the paragraph and graphs below.
In a hypothetical situation, the National Park Service, which administers Grand Canyon National Park in Arizona, builds a footbridge over the Colorado River at the bottom of the canyon. The footbridge permits interspersal of two closely related antelope squirrels. Previously, one type of squirrel had been restricted to the terrain south of the river, and the other type had been restricted to terrain on the north side of the river. Immediately before and ten years after the bridge's completion, ten antelope squirrels from both sides of the river were collected, blood samples were taken, and frequencies of alleles unique to the two types of antelope squirrels were determined (see graphs below).


Which of the following would be a position held by an adherent of the punctuated equilibrium theory?

A)A new species forms most of its unique features as it comes into existence and then changes little for the duration of its existence.
B)One should expect to find many transitional fossils left by organisms in the process of forming new species.
C)Given enough time, most existing species will gradually evolve into new species.
D)Natural selection is unimportant as a mechanism of evolution.