43) Which section of sea-floor crust should have the thickest layer of overlying sediment, assuming a
continuous rate of sediment deposition?
A) A
B) B
C) C
D) D
E) E
44) If a particular marine organism is fossilized in the sediments immediately overlying the igneous rock
at the arrow labeled “II,” at which other location, labeled A—E, would a search be most likely to find
more fossils of this organism?
A) B only
B) C only
C) D only
D) B and C
E) C and D
45) How many other bands of sea-floor crust in Figure 25.1 have the same magnetic polarity as the crust
that directly straddles the rift valley?
A) two bands
B) four bands
C) six bands
D) eight bands
E) ten bands
46) Assuming that the rate of sea-floor spreading was constant during the 1-million-year period depicted
above, what should be the approximate age of marine fossils found in undisturbed sedimentary rock
immediately overlying the igneous rock at the arrow labeled “II”?
A) 10,000 years
B) 250,000 years
C) 400,000 years
D) 1,000,000 years
The following questions refer to the paragraph below.
A sediment core is removed from the floor of an inland sea. The sea has been in existence, off and on,
throughout the entire time that terrestrial life has existed. Researchers wish to locate and study the
terrestrial organisms fossilized in this core. The core is illustrated as a vertical column, with the top of
the column representing the most recent strata and the bottom representing the time when land was first
colonized by life.
Figure 25.2
47) If arrows indicate locations in the column where fossils of a particular type (see key above) first
appear, then which core in Figure 25.2 has the most accurate arrangement of fossils?
A) core A
B) core B
C) core C
D) core D
48) Which of the following reasons may explain why the sediment core lacks fossils of dragonflies with
3-feet wingspans?
1. This particular sediment core includes the correct stratum, but the part of the stratum captured by the
core lacks such fossils.
2. The sea was not present at this site during the time that 3-feet dragonflies existed.
3. Dragonflies have no hard parts, such as exoskeletons, to fossilize.
4. The sediments containing these fossils at this site may have been eroded away during a time when the
sea had receded from this site.
5. Dragonflies are terrestrial; therefore, fossils of terrestrial organisms should not be expected in the
sediments of seas.
A) 1 only
B) 3 only
C) 5 only
D) 2 or 4
E) 1, 2, or 4
49) In order to properly interpret sediment cores, it is necessary to apply the principle of
A) catastrophism.
B) superposition.
C) punctuated equilibrium.
D) uniformitarianism.
E) gradualism.
50) Assuming the existence of fossilized markers for each of the following chemicals, what is the
sequence in which they should be found in this sediment core, working from ancient sediments to recent
sediments?
1. chitin coupled with protein
2. chlorophyll
3. bone
4. cellulose
A) 2, 4, 3, 1
B) 2, 4, 1, 3
C) 4, 2, 1, 3
D) 4, 2, 3, 1
51) In order to assign absolute dates to fossils in this sediment core, it would be most helpful if
A) we knew the order in which the fossils occurred in the core.
B) the sediments had not been affected by underwater currents during their deposition.
C) volcanic ash layers were regularly interspersed between the sedimentary strata.
D) metamorphic rock strata alternated with sedimentary rock strata.
E) fossils throughout the column had equal ratios of a parental radioisotope to its daughter isotope.
Figure 25.3
52) According to the theory of sea-floor spreading, oceanic islands, such as the Hawaiian Islands
depicted in Figure 25.3, form as oceanic crustal plates move over a stationary “hot spot” in the mantle.
Currently, the big island of Hawaii is thought to be over a hot spot, which is why it is the only one of the
seven islands that has active volcanoes. What should be true of the island of Hawaii?
1. Scientists in search of ongoing speciation events are more likely to find them here than on the other
six islands.
2. Its species should be more closely related to those of nearer islands than to those of farther islands.
3. It should have a rich fossil record of terrestrial organisms.
4. There is a good chance of finding endemic species on this island.
5. On average, it should have fewer species per unit surface area than the other six islands.
A) 1, 2, and 3
B) 1, 2, and 5
C) 1, 2, 3, and 4
D) 1, 2, 4, and 5
E) 2, 3, 4, and 5
53) Hawaii is the most southeastern of the seven islands and is also closest to the sea-floor spreading
center from which the Pacific plate originates, which lies about 5,600 km further to the southeast.
Assuming equal sedimentation rates, what should be the location of the thickest sediment layer and,
thus, the area with the greatest diversity of fossils above the oceanic crust?
A) between the island of Hawaii and the sea-floor spreading center
B) around the base of the island of Hawaii
C) around the base of Kauai, the oldest of the Hawaiian islands
D) where the islands are most concentrated (highest number of islands per unit surface area)
54) Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago),
the evolution of life on this new island should have been most strongly influenced by
A) genetic bottleneck.
B) sexual selection.
C) habitat differentiation.
D) founder effect.
55) Upon being formed, oceanic islands, such as the Hawaiian Islands, should feature what
characteristic, leading to which phenomenon?
A) mass extinctions, leading to bottleneck effect
B) major evolutionary innovations, leading to rafting to nearby continents
C) a variety of empty ecological niches, leading to adaptive radiation
D) adaptive radiation, leading to founder effect
E) overcrowding, leading to rafting to nearby lands
Scenario Questions
Refer to the following information to answer the questions below.
Fossils of Lystrosaurus, a dicynodont therapsid, are most common in parts of modern-day South
America, South Africa, Madagascar, India, South Australia, and Antarctica. It apparently lived in arid
regions, and was mostly herbivorous. It originated during the mid-Permian period, survived the Permian
extinction, and dwindled by the late Triassic, though there is evidence of a relict population in Australia
during the Cretaceous period. The dicynodonts had two large tusks, extending down from their upper
jaws. The tusks were not used for food gathering, and in some species were limited to males. Food was
gathered using an otherwise toothless beak. Judging from the fossil record in sedimentary rocks, these
pig-sized organisms were the most common mammal-like reptiles of the Permian.
56) Anatomically, what was true of Lystrosaurus?
A) Its jaw would have been hinged the same way as the jaws of the early reptiles were hinged.
B) It was a tetrapod.
C) It had skin without scales, typical of modern amphibians.
D) It would have had no temporal fenestra in its skull.
57) How many of Lystrosaurus’ features below can help explain why these organisms fossilized so
abundantly?
I. the presence of hard parts, such as tusks
II. its arid environment
III. its persistence across at least two geological eras
IV. its widespread geographic distribution
V. its mixture of reptilian and mammalian features
A) only one of these statements
B) two of these statements
C) three of these statements
D) four of these statements
E) all five of these statements
58) Which of the following is the most likely explanation for the modern-day distribution of dicynodont
fossils?
A) There had been two previous supercontinents that existed at different times long before the Permian
period.
B) The dicynodonts were evenly distributed throughout all of Pangaea.
C) The dicynodonts were distributed more abundantly throughout Gondwanaland than throughout any
other land mass.
D) The dicynodonts were amphibious and able to swim long distances.
E) The dicynodonts could survive for periods of months aboard “rafts” of vegetation, few of which made
their way to the northern hemisphere.
59) If an increase in dicynodont species diversity (in other words, number of species) occurred soon
after the Permian extinction, and if it occurred for the same general reason usually given for the increase
in mammalian diversity following the Cretaceous extinction, then it should be attributed to
A) an innovation among the dicynodonts that allowed them to fill brand-new niches.
B) the availability of previously occupied niches.
C) the extinction of the dinosaurs (except the birds).
D) their outcompetition of many other terrestrial organisms.
The following questions are based on the observation that several dozen different proteins comprise the
prokaryotic flagellum and its attachment to the prokaryotic cell, producing a highly complex structure.
60) If the complex protein assemblage of the prokaryotic flagellum arose by the same general processes
as those of the complex eyes of molluscs (such as squids and octopi), then
A) natural selection cannot account for the rise of the prokaryotic flagellum.
B) ancestral versions of this protein assemblage were either less functional or had different functions
than modern prokaryotic flagella.
C) scientists should accept the conclusion that neither eyes nor flagella could have arisen by evolution.
D) we can conclude that both of these structures must have arisen through the direct action of an
“intelligent designer.”
21
61) Certain proteins of the complex motor that drives bacterial flagella are modified versions of proteins
that had previously belonged to plasma membrane pumps. This evidence supports the claim that
A) some structures are so complex that natural selection cannot, and will not, explain their origins.
B) the power of natural selection allows it to act in an almost predictive fashion, producing organs that
will be needed in future environments.
C) the motors of bacterial flagella were originally synthesized abiotically.
D) natural selection can produce new structures by coupling together parts of other structures.
E) bacteria that possess flagella must have lost the ability to pump certain chemicals across their plasma
membranes.
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, for their flight wings are absent, and
their balancing organs (in other words, 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.
62) If these fly species lost the ability to fly independently of each other as a result of separate mutation
events in each lineage, then the flightless condition in these species could be an example of
A) adaptive radiation.
B) species selection.
C) sexual selection.
D) allometric growth.
E) habitat differentiation.
63) In each fly species, the entire body segment that gave rise to the original flight wings is missing. The
mutation(s) that led to the flightless condition could have
A) duplicated all of the Hox genes in these flies’ genomes.
B) altered the nucleotide sequence within a Hox gene.
C) altered the expression of a Hox gene.
D) all three of the above responses
E) two of the above answers are correct
64) 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
species W and Y
A) have genomes that are still similar enough for successful meiosis to occur in hybrid flies.
B) have more genetic similarity with each other than either did with the other two species.
C) may fuse into a single species if their hybrids remain fertile over the course of many generations.
D) Three of the above statements are correct.
E) Two of the statements above are correct.
65) Which of these fly organs, as they exist in current fly populations, best fits the description of an
exaptation?
A) wings
B) balancing organs
C) mouthparts
D) thoraxes
E) walking appendages
The following questions refer to the description below.
All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated,
the gene Pax–6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye
parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence
differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit
flies, even though vertebrates and invertebrates last shared a common ancestor more than 500 million
years ago.
66) The appearance of Pax-6 in all animals with eyes can be explained in multiple ways. Based on the
information above, which explanation is most likely?
A) Pax-6 in all of these animals is not homologous; it arose independently in many different animal
phyla due to intense selective pressure favoring vision.
B) The Pax-6 gene is really not “one” gene. It is many different genes that, over evolutionary time and
due to convergence, have come to have a similar nucleotide sequence and function.
C) The Pax-6 gene was an innovation of an ancestral animal of the early Cambrian period. Animals with
eyes or eyespots are descendants of this ancestor.
D) The perfectly designed Pax-6 gene appeared instantaneously in all animals created to have eyes or
eyespots.
67) Fruit fly eyes are of the compound type, which is structurally very different from the camera-type
eyes of mammals. Even the camera-type eyes of molluscs, such as octopi, are structurally quite different
from those of mammals. Yet, fruit flies, octopi, and mammals possess very similar versions of Pax-6.
The fact that the same gene helps produce very different types of eyes is most likely due to
A) the few differences in nucleotide sequence among the Pax-6 genes of these organisms.
B) variations in the number of Pax-6 genes among these organisms.
C) the independent evolution of this gene at many different times during animal evolution.
D) differences in the control of Pax-6 expression among these organisms.
68) Pax-6 usually causes the production of a type of light-receptor pigment. In vertebrate eyes, though, a
different gene (the rh gene family) is responsible for the light-receptor pigments of the retina. The rh
gene, like Pax-6, is ancient. In the marine ragworm, for example, the rh gene causes production of c-
opsin, which helps regulate the worm’s biological clock. Which of these most likely accounts for
vertebrate vision?
A) The Pax-6 gene mutated to become the rh gene among early mammals.
B) During vertebrate evolution, the rh gene for biological clock opsin was co-opted as a gene for visual
receptor pigments.
C) In animals more ancient than ragworms, the rh gene(s) coded for visual receptor pigments; in
lineages more recent than ragworms, rh has flip-flopped several times between producing biological
clock opsins and visual receptor pigments.
D) Pax-6 was lost from the mammalian genome, and replaced by the rh gene much later.
End-of-Chapter Questions
The following questions are from the end-of–chapter “Test Your Understanding” section in Chapter 25
of the textbook.
69) Fossilized stromatolites
A) all date from 2.7 billion years ago.
B) formed around deep-sea vents.
C) resemble structures formed by bacterial communities that are found today in some warm, shallow,
salty bays.
D) provide evidence that plants moved onto land in the company of fungi around 500 million years ago.
E) contain the first undisputed fossils of eukaryotes and date from 2.1 billion years ago.
70) The oxygen revolution changed Earth’s environment dramatically. Which of the following took
advantage of the presence of free oxygen in the oceans and atmosphere?
A) the evolution of cellular respiration, which used oxygen to help harvest energy from organic
molecules
B) the persistence of some animal groups in anaerobic habitats
C) the evolution of photosynthetic pigments that protected early algae from the corrosive effects of
oxygen
D) the evolution of chloroplasts after early protists incorporated photosynthetic cyanobacteria
E) the evolution of multicellular eukaryotic colonies from communities of prokaryotes
71) Which factor most likely caused animals and plants in India to differ greatly from species in nearby
southeast Asia?
A) The species have become separated by convergent evolution.
B) The climates of the two regions are similar.
C) India is in the process of separating from the rest of Asia.
D) Life in India was wiped out by ancient volcanic eruptions.
E) India was a separate continent until 45 million years ago.
72) Adaptive radiations can be a direct consequence of four of the following five factors. Select the
exception.
A) vacant ecological niches
B) genetic drift
C) colonization of an isolated region that contains suitable habitat and few competitor species
D) evolutionary innovation
E) an adaptive radiation in a group of organisms (such as plants) that another group uses as food
73) Which of the following steps has not yet been accomplished by scientists studying the origin of life?
A) synthesis of small RNA polymers by ribozymes
B) abiotic synthesis of polypeptides
C) formation of molecular aggregates with selectively permeable membranes
D) formation of protocells that use DNA to direct the polymerization of amino acids
E) abiotic synthesis of organic molecules
74) A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb
bud instead of farther back helped make possible the evolution of the tetrapod limb. This type of change
is illustrative of
A) the influence of environment on development.
B) paedomorphosis.
C) a change in a developmental gene or its regulation that altered the spatial organization of body parts.
D) heterochrony.
E) gene duplication.
75) A swim bladder is a gas-filled sac that helps fish maintain buoyancy. The evolution of the swim
bladder from lungs of an ancestral fish is an example of
A) an evolutionary trend.
B) exaptation.
C) changes in Hox gene expression.
D) paedomorphosis.
E) adaptive radiation.