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, these conditions will most likely lead
to
A) fusion.
B) reinforcement.
C) stability.
D) further speciation events.

reinforcement.

Which type of reproductive isolation operates to keep the mosquitofish isolated, even when
fish from different ponds are reunited in the same body of water?
A) behavioral isolation
B) habitat isolation
C) temporal isolation
D) mechanical isolation
E) gametic isolation

behavioral isolation

In which habitat should one find snapping shrimp most closely related to shrimp that live in
habitat A4?
A) A3
B) A5
C) B4
D) either A3 or A5
E) any species from any one of the side A habitats

B4

Which of these habitats is likely to harbor the youngest species?
A) A5
B) B4
C) A3
D) B2
E) A1

A1

Which habitats should harbor snapping shrimp species with the greatest degree of genetic
divergence from each other?
A) A1 and A5
B) A1 and B5
C) B5 and B1
D) A5 and B5
E) Both A1/A5 and B1/B5 should have the greatest, but equal amounts of, genetic divergence.

A5 and B5

Which factor is most important for explaining why there are equal numbers of snapping
shrimp species on either side of the isthmus?
A) the relative shortness of time they have been separated
B) the depth of the ocean
C) the number of actual depth habitats between the surface and the sea floor
D) the elevation of the isthmus above sea level
E) the depth of the canal

the relative shortness of time they have been separated

There are currently two large, permanent bridges that span the Panama Canal. The bridges are
about 8 miles apart. If snapping shrimp avoid swimming at night and avoid swimming under
shadows, then what do these bridges represent for the snapping shrimp?
A) sources of refuge
B) geographic barriers
C) sources of a hybrid zone between the two bridges
D) sources for increased gene flow

geographic barriers

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?
A) A5 and B5
B) A3 and B3
C) A1 and B1
D) either A1 and A2, or B1 and B2
E) A1–A3 and B1–B3 have equal likelihoods of harboring snapping shrimp species that can
hybridize.

A1 and B1

The data in these graphs indicate that
A) a hybrid zone was established after the completion of the bridge.
B) there was no migration between the two squirrel populations after the bridge was completed.
C) gene flow occurred from one type of squirrel into the gene pool of the other type of squirrel.
D) two-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.

two-way migration of squirrels occurred across the bridge, but without hybridization.

Which species is most closely related to species W?
A) V is most closely related to species W.
B) X is most closely related to species W.
C) Y and Z are equally closely related to W.
D) It is not possible to say from this tree.

V is most closely related to species W.

Which species is least expected to have a good record of transitional fossils; in other words,
which species' fossils, if present at all, are expected only in relatively superficial (i.e., shallow)
strata?
A) V
B) W
C) X
D) Y
E) Z

V

Which of these five species originated earliest and appeared suddenly in the fossil record?
A) V
B) W
C) X
D) Y
E) Z

W

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.

A single clade (i.e., a group of species that share a common ancestor) can exhibit both
gradualism and punctuated equilibrium.

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.

V; shared a common ancestor with X most recently

Which type of reproductive isolation operates to keep the mosquitofish isolated, even when
fish from different ponds are reunited in the same body of water?
A) behavioral isolation
B) habitat isolation
C) temporal isolation
D) mechanical isolation
E) gametic isolation

behavioral isolation

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
A) 1 and 3
B) 2 and 3
C) 2 and 4
D) 3 and 4
E) 3 and 5

3 and 5

Why should deepwater shrimp on different sides of the isthmus have diverged from each
other earlier than shallow-water shrimp?
A) They have been geographically isolated from each other for a longer time.
B) Cold temperatures, associated with deep water, have accelerated the mutation rate, resulting
in faster divergence in deepwater shrimp.
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.
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.

They have been geographically isolated from each other for a longer time.

The predatory fish rely on visual cues and speed to capture mosquitofish. Mosquitofish rely
on speed and visual cues to avoid the predatory fish. Which adaptation(s) might help the
predators survive in ponds that are home to faster mosquitofish?
1. directional selection for increased speed
2. stabilizing selection for speed that matches that of the mosquitofish
3. change in hunting behavior that replaces reliance on visual cues with reliance on tactile cues,
which can be used to hunt at night
4. change in hunting behavior that eliminates speed in favor of better camouflage, which permits
an ambush strategy
A) 1 only
B) 2 only
C) either 1 or 3
D) either 2 or 3
E) 1, 3, or 4

1, 3, or 4

The largest unit within which gene flow can readily occur is a
A) population.
B) species.
C) genus.
D) hybrid.
E) phylum.

species.

Males of different species of the fruit fly Drosophila that live in the same parts of the
Hawaiian Islands have different elaborate courtship rituals. These rituals involve fighting other
males and making 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

behavioral isolation

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.

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.

Bird guides once listed the myrtle warbler and Audubon’s warbler as distinct species.
Recently, these birds have been reclassified 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 survive and reproduce well.
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.

The two forms interbreed often in nature, and their offspring survive and reproduce well.

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.

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.

28.