AP Biology Chapter 24 Flashcards

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

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

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

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

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

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

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 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.

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 overlap.
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
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

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.

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila
yakuba inhabits the islandʹs 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 speciesʹ
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

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila
yakuba inhabits the islandʹs 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 speciesʹ
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.

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila
yakuba inhabits the islandʹs 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 speciesʹ
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

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila
yakuba inhabits the islandʹs 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 speciesʹ
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

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila
yakuba inhabits the islandʹs 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 speciesʹ
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)?

On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly exist. Drosophila
yakuba inhabits the islandʹs 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 speciesʹ
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.

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 bridgeʹs 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.

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 bridgeʹs 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.

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 species.
C) Given enough time, most existing species will gradually evolve into new species.
D) Natural selection is unimportant as a mechanism of evolution.

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.

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.