12
Use the following description to answer the question(s) below.
On the Bahamian island of Andros, mosquitofish populations live in various, now-isolated,
freshwater ponds that were once united. Currently, some predator-rich ponds have mosquitofish
that can swim in short, fast bursts; other predator-poor ponds have mosquitofish that can swim
continuously for a long time. When placed together in the same body of water, the two kinds of
female mosquitofish exhibit exclusive breeding preferences.
35) 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 5
Use the following description to answer the question(s) below.
In the ocean, on either side of the Isthmus of Panama, are thirty species of snapping shrimp;
some are shallow-water species, others are adapted to deep water. There are fifteen species on
the Pacific side and fifteen different species on the Atlantic side. The Isthmus of Panama started
rising about ten million years ago. The oceans were completely separated by the isthmus about
three million years ago.
In the following figure, the isthmus separates the Pacific Ocean on the left (side A) from the
Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into
five depth habitats (1-5), with 1 being the shallowest.
36) 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.
37) 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
38) Which of these habitats is likely to harbor the most recently diverged species?
A) A5
B) B4
C) A3
D) A1
39) 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) A5 and B5
D) Both A1/A5 and B1/B5 should have the greatest, but equal amounts of, genetic divergence.
40) 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
41) The Panama Canal was completed in 1914, and its depth is about fifty 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) A1-A3 and B1-B3 have equal likelihoods of harboring snapping shrimp species that can
hybridize.
42) 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) 14
B) 16
C) 28
D) 56
43) A small number of birds arrive on an island from a neighboring larger island. This small
population begins to adapt to the new food plants available on the island, and their beaks begin to
change. About twice a year, one or two more birds from the neighboring island arrive. These
new arrivals _____.
A) speed up the process of speciation
B) tend to promote adaptation to the new food plants
C) tend to retard adaptation to the new food plants
D) represent a colonizing event
44) Male frogs give calls that attract female frogs to approach and mate. Researchers examined
mating calls of closely related tree frogs in South America. If reinforcement is occurring, what
would you expect if you compare the calls of the two species in zones of sympatry versus zones
of allopatry?
A) Calls would be about the same in both areas.
B) Calls would be more similar in areas of sympatry.
C) Calls would be more different in areas of sympatry.
45) Male frogs give calls that attract female frogs to approach and mate. Researchers examined
mating calls of closely related but separate species of tree frogs in South America. What
outcomes could possibly occur where the ranges of two species overlap?
I) The species will interbreed, eventually fusing over time.
II) A stable hybrid zone will form if hybrids are better adapted to the area of overlap than either
parent species is.
III) Species will continue to diverge and be isolated by behavioral or genetic mechanisms.
A) I
B) II
C) III
D) I, II, and III
46) Reinforcement is most likely to occur when _____.
A) the environment is changing
B) hybrids have lower fitness than either parent population
C) prezygotic isolating mechanisms are in place
D) gene flow is low
47) The phenomenon of fusion is likely to occur when, after a period of geographic isolation,
two populations meet again and _____.
A) an increasing number of infertile hybrids is produced over the course of the next one hundred
generations
B) no reproduction occurs in the hybrid zone
C) an increasing number of viable, fertile hybrids is produced over the course of the next one
hundred generations
D) a decreasing number of viable, fertile hybrids is produced over the course of the next one
hundred generations
48) A hybrid zone is properly defined as _____.
A) an area where the ranges of two closely related species overlap, but do not interbreed
B) an area where mating occurs between members of two closely related species, producing
viable offspring
C) a zone where sterile hybrids form, kept separate by postzygotic barriers
D) an area where members of two closely related species intermingle, but gene flow is prevented
by prezygotic barriers
49) In hybrid zones where reinforcement is occurring, we should see a decline in _____.
A) gene flow between distinct gene pools
B) speciation
C) the genetic distinctness of two gene pools
D) mutation rates
50) Other than predation by introduced Nile perch, the most likely explanation for the recent
decline in cichlid species diversity in Lake Victoria is _____.
A) reinforcement
B) fusion
C) stability
D) polyploidy
51) A narrow hybrid zone separates the toad species Bombina bombina and Bombina variegata.
What is true of those alleles that are unique to the parental species?
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 than in toad populations
distant from the hybrid zone.
D) Their allele frequency on one edge of the hybrid zone should roughly equal their frequency
on the opposite edge of the hybrid zone.
Use the following description to answer the question(s) 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 two hundred miles away. At higher elevations, and only on Sao Tomé, is found the
very closely related Drosophila santomea. The two species can hybridize, though male hybrids
are sterile. A hybrid zone exists at middle elevations, though hybrids there are greatly
outnumbered by D. santomea. Studies of the two species’ nuclear genomes reveal that D. yakuba
on the island is more closely related to mainland D. yakuba than to D. santomea (2n = 4 in both
species). Sao Tomé rose from the Atlantic Ocean about fourteen million years ago.
52) 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) arrived on the island before D. yakuba
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.
Use the following description to answer the question(s) below.
On the Bahamian island of Andros, mosquitofish populations live in various, now-isolated,
freshwater ponds that were once united. Currently, some predator-rich ponds have mosquitofish
that can swim in short, fast bursts; other predator-poor ponds have mosquitofish that can swim
continuously for a long time. When placed together in the same body of water, the two kinds of
female mosquitofish exhibit exclusive breeding preferences.
53) What is the best way to promote fusion between two related populations of mosquitofish, one
of which lives in a predator-rich pond and the other of which lives in a predator-poor pond?
A) Build a canal linking the two ponds that permits free movement of mosquitofish, but not of
predators.
B) Transfer only female mosquitofish from a predator-rich pond to a predator-poor pond.
C) Perform a reciprocal transfer of females between predator-rich and predator-poor ponds.
D) Remove predators from a predator-rich pond and transfer them to a predator-poor pond.
54) Suppose that a group of male pied flycatchers migrated from a region where there were no
collared flycatchers to a region where both species were present. Assuming events like this are
very rare, which of the following scenarios is LEAST likely?
A) Migrant pied males would produce fewer offspring than would resident pied males.
B) Pied females would rarely mate with collared males.
C) Migrant males would mate with collared females more often than with pied females.
D) The frequency of hybrid offspring would decrease.
The following questions refer to this hypothetical situation.
A female fly, full of fertilized eggs, is swept by high winds to an island far out to sea. She is the
first fly to arrive on this island and the only fly to arrive in this way. Thousands of years later,
her numerous offspring occupy the island, but none of them resembles her. There are, instead,
several species, each of which eats only a certain type of food. None of the species can fly and
their balancing organs (halteres) are now used in courtship displays. The male members of each
species bear modified halteres that are unique in appearance to their species. Females bear
vestigial halteres. The ranges of all of the daughter species overlap.
55) Fly species W, found in a certain part of the island, produces fertile offspring with species Y.
Species W does not produce fertile offspring with species X or Z. If no other species can
hybridize, then which of the following statements about species W and Y are true?
I) Species W and Y have genomes that are still similar enough for successful meiosis to occur
in hybrid flies.
II) Species W and Y have more genetic similarity with each other than either did with the other
two species.
III) Species W and Y may fuse into a single species if their hybrids remain fertile over the course
of many generations.
A) Only I is correct.
B) Only II is correct.
C) Only III is correct.
D) I, II, and III are correct.
56) 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 in one generation
C) speciation occurred rapidly in geologic time
D) the species will consequently have a relatively short existence, compared with other species
57) 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 gradually give rise to 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
58) 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 small genetic changes over vast expanses of time
C) must begin with the geographic isolation of a small, frontier population
D) can involve changes to a single gene
59) According to the biological species concept, for speciation to occur, _____.
A) the number of chromosomes in the gene pool must change
B) changes to centromere location or chromosome size must occur within the gene pool
C) large numbers of genes that affect numerous phenotypic traits must change
D) at least one gene, affecting at least one phenotypic trait, must change
The questions below refer to the following evolutionary tree, in which the horizontal axis
represents time (present time is on the far right) and the vertical axis represents morphological
change.
60) Which conclusion can be drawn from this evolutionary tree?
A) A single clade (that is, a group of species that share a common ancestor) can include species
that formed by gradualism and other species that formed by punctuated equilibrium.
B) A single clade (that is, a group of species that share a common ancestor) will either include
species that formed by gradualism or species that formed by punctuated equilibrium.
C) Assuming that the tip of each line represents a species, there are five extant (that is, not
extinct) species resulting from the earliest common ancestor.
D) Species X and Z best represent species that evolved by punctuated equilibrium.