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AP Biology Chapter 24

The Origin of Species
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
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 speciesʹ gene pool to the otherʹs gene pool.
C) They are unable to produce hybrid offspring upon interbreeding.
D) Their reproductive isolation from each other is complete.
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
Which species concept is currently most popular among most biologists?
A) phylogenetic
B) ecological
C) biological
D) morphological
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
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
What was the species concept most used by Linnaeus?
A) biological
B) morphological
C) ecological
D) phylogenetic
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
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
One species lives only in tree holes; another species lives only in streams.
A) behavioral
B) gametic
C) habitat
D) temporal
E) mechanical
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
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
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
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
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
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
Theoretically, the production of sterile mules by interbreeding between female horses and male donkeys
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.
The biological species concept is inadequate for grouping
A) plants.
B) parasites.
C) asexual organisms.
D) animals that migrate.
E) sympatric populations.
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
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
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 fleasʹ 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
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.
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.
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
E) They interbreed in the region of overlap, but produce sterile offspring.
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.
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
Beetle pollinators of a particular plant are attracted to its flowersʹ 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
A) allopatric speciation, ecological isolation
B) sympatric speciation, habitat differentiation
C) allopatric speciation, behavioral isolation
D) sympatric speciation, sexual selection
E) sympatric speciation, allopolyploidy
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.
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.
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.
A hybrid zone is properly defined as
A) an area where two closely related speciesʹ 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.
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
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.
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.
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 allelesʹ 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.
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
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.
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
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
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.
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.
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.
According to the concept of punctuated equilibrium, the ʺsuddenʺ 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.
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.
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
C) Given enough time, most existing species will gradually evolve into new species.
D) Natural selection is unimportant as a mechanism of evolution.
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.
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.
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
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.
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
Which of these five species originated earliest and appeared suddenly in the fossil record?
A) V
B) W
C) X
D) Y
E) Z
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.
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.
The largest unit within which gene flow can readily occur is a
A) population.
B) species.
C) genus.
D) hybrid.
E) phylum.
Bird guides once listed the myrtle warbler and Audubonʹs 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.
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
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.
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.
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.