In what way were conditions on the early Earth of more than 3 billion years ago different
from those on todayʹs Earth?
A) Only early Earth had water vapor in its atmosphere.
B) Only early Earth was intensely bombarded by large space debris.
C) Only early Earth had an oxidizing atmosphere.
D) Less ultraviolet radiation penetrated Earthʹs early atmosphere.
E) Earthʹs early atmosphere had significant quantities of ozone.

B

What is true of the amino acids that might have been delivered to Earth within
carbonaceous chondrites?
A) They had the same proportion of L and D isomers as Earth does today.
B) The proportion of the amino acids was similar to those produced in the Miller-Urey
experiment.
C) There were fewer kinds of amino acids on the chondrites than are found in living
organisms today.
D) They were delivered in the form of polypeptides.

B

Which of the following is the correct sequence of these events in the origin of life?
I. formation of protobionts
II. synthesis of organic monomers
III. synthesis of organic polymers
IV. formation of DNA-based genetic systems
A) I, II, III, IV
B) I, III, II, IV
C) II, III, I, IV
D) IV, III, I, II
E) III, II, I, IV

C

Which is a defining characteristic that all protobionts had in common?
A) the ability to synthesize enzymes
B) a surrounding membrane or membrane-like structure
C) RNA genes
D) a nucleus
E) the ability to replicate RNA

B

Although absolute distinctions between the ʺmost evolvedʺ protobiont and the first living
cell are unclear, biologists generally agree that one major difference is that the typical
protobiont could not
A) possess a selectively permeable membrane boundary.
B) perform osmosis.
C) grow in size.
D) perform controlled, precise reproduction.
E) absorb compounds from the external environment

D

The first genes on Earth were probably
A) DNA produced by reverse transcriptase from abiotically produced RNA.
B) DNA molecules whose information was transcribed to RNA and later translated in
polypeptides.
C) auto-catalytic RNA molecules.
D) RNA produced by autocatalytic, proteinaceous enzymes.
E) oligopeptides located within protobionts.

C

RNA molecules can both carry genetic information and be catalytic. This supports the
proposal that
A) RNA was the first hereditary information.
B) protobionts had an RNA membrane.
C) RNA could make energy.
D) free nucleotides would not have been necessary ingredients in the synthesis of new
RNA molecules.
E) RNA is a polymer of amino acids.

A

What probably accounts for the switch to DNA-based genetic systems during the evolution
of life on Earth?
A) DNA is chemically more stable and replicates with fewer errors (mutations) than
RNA.
B) Only DNA can replicate during cell division.
C) RNA is too involved with translation of proteins and cannot provide multiple
functions.
D) DNA forms the rod-shaped chromosomes necessary for cell division.
E) Replication of RNA occurs too slowly

A

The synthesis of new DNA requires the prior existence of oligonucleotides to serve as
primers. On Earth, these primers are small RNA molecules. This latter observation is
evidence in support of the hypothesized existence of
A) a snowball Earth.
B) earlier genetic systems than those based on DNA.
C) the abiotic synthesis of organic monomers.
D) the delivery of organic matter to Earth by meteors and comets.
E) the endosymbiotic origin of mitochondria and chloroplasts.

B

Several scientific laboratories across the globe are involved in research concerning the
origin of life on Earth. Which of these questions is currently the most problematic and
would have the greatest impact on our understanding if we were able to answer it?
A) How can amino acids, simple sugars, and nucleotides be synthesized abiotically?
B) How can RNA molecules catalyze reactions?
C) How did RNA sequences come to carry the code for amino acid sequences?
D) How could polymers involving lipids and/or proteins form membranes in aqueous
environments?
E) How can RNA molecules act as templates for the synthesis of complementary RNA
molecules?

C

) Several scientific laboratories across the globe are involved in research concerning the
origin of life on Earth. Which graph below, if the results were produced abiotically, would
have the greatest promise for revealing important information about the origin or Earthʹs
first genetic system?

B

If natural selection in a particular environment favored genetic systems that permitted the
production of daughter ʺcellsʺ that were genetically dissimilar from the mother ʺcells,ʺ then
one should expect selection for
I. polynucleotide polymerase with low mismatch error rates.
II. polynucleotide polymerases without proofreading capability.
III. batteries of efficient polynucleotide repair enzymes.
IV. polynucleotide polymerases with proofreading capability.
V. polynucleotide polymerases with high mismatch error rates.
A) I only
B) I and IV
C) I, III, and IV
D) II and V
E) II, III and V

D

If relatively small carbonaceous chondrites from space were a significant source of Earthʹs
original amino acids, then which two of these would have been most important in
permitting their organic materials to survive impact with Earth?
I. Carbonaceous chondrites must contain no D-amino acids.
II. Earthʹs early atmosphere must have had little free oxygen.
III. The chondrites must have arrived on Earth before 4.2 billion years ago.
IV. Earthʹs early atmosphere must have been dense enough to dramatically slow the
chondrites before they impacted.
V. The chondrites must have impacted land, rather than a large body of water.
A) I & II
B) II & III
C) II & IV
D) II & V
E) III & IV

C

If the half-life of carbon-14 is about 5,730 years, then a fossil that has one-sixteenth the
normal proportion of carbon-14 to carbon-12 should be about how many years old?
A) 1,400
B) 2,800
C) 11,200
D) 16,800
E) 22,400

E

Which measurement would help determine absolute dates by radiometric means?
A) the accumulation of the daughter isotope
B) the loss of parent isotopes
C) the loss of daughter isotopes
D) all three of these
E) only A and B

E

How many half-lives should have elapsed if 6.25% of the parent isotope remains in a fossil
at the time of analysis?
A) one
B) two
C) three
D) four
E) five

D

Approximately how far back in time does the fossil record extend?
A) 6,000 years
B) 3,500,000 years
C) 6,000,000 years
D) 3,500,000,000 years
E) 5,000,000,000,000 years

D

) Assuming that the rate of sea-floor spreading was constant during the 1-million-year
period depicted above, Earthʹs magnetic field has undergone reversal at an average rate of
once every
A) 10,000 years.
B) 25,000 years.
C) 100,000 years.
D) 250,000 years.
E) 1,000,000 years

D

If a particular marine organism is fossilized in the sediments immediately overlying the
igneous rock at the arrow labeled ʺII,ʺ at which other location, labeled A—E, would a
search be most likely to find more fossils of this organism?
A) A
B) B
C) C
D) D
E) E

C

Earthʹs current magnetic field is the same as it had been when which sea-floor areas
solidified?
I. area B
II. area C
III. area D
IV. area E
A) I only
B) II only
C) I and II
D) I and III
E) II and IV

E

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
ʺIIʺ?
A) 10,000 years
B) 250,000 years
C) 500,000 years
D) 1,000,000 years

C

Argon-40, the daughter isotope of potassium-40, is a gas. Elemental potassium has an
atomic mass of about 39. If the submersible robot (which is equipped with a drill that is
long enough to get to the igneous rock) ascends from depth too quickly, gases trapped
within igneous rock may rapidly expand, fracture the rock, and escape from the sample
before it can be dated aboard the floating research vessel. Rock samples can also absorb
argon gas. Which of these techniques has the highest chance of providing inaccurate dates
of igneous rocks distant from the rift valley, and what type of inaccuracy would it cause?
A) if the date of the rock is determined by comparing the ratio of potassium-40 to
potassium-39, underestimation of age
B) if the submersible robot is retrieved from the sea floor at a very slow speed,
overestimation of age
C) if the submersible robot is equipped with a decompression chamber for the samples,
underestimation of age
D) if the submersible robot keeps the sample in a chamber of pure argon at high
pressure, overestimation of age

D

What is true of the fossil record of mammalian origins?
A) It is a good example of punctuated equilibrium.
B) It shows that mammals and birds evolved from the same kind of dinosaur.
C) It includes transitional forms with progressively specialized teeth.
D) It indicates that mammals and dinosaurs did not overlap in geologic time.
E) It includes a series that shows the gradual change of scales into fur.

C

If a fossil is encased in a stratum of sedimentary rock without any strata of igneous rock
(e.g., lava, volcanic ash) nearby, then it should be
A) easy to determine the absolute age of the fossil, because the radioisotopes in the
sediments will not have been ʺresetʺ by the heat of the igneous rocks.
B) easy to determine the absolute age of the fossil, because the igneous rocks will not
have physically obstructed the deposition of sediment of a single age next to the
fossil.
C) difficult to determine the absolute age of the fossil, because the ʺmarker fossilsʺ
common to igneous rock will be absent.
D) difficult to determine the absolute age of the fossil, because radiometric dating of
sedimentary rock is less accurate than that of igneous rock.

D

Letʹs say that a hypothetical submersible robot was used to collect samples of sedimentary
rock from the sea floor along the section illustrated. The robot moved back and forth along
the transect, collecting first from site A, then site III, then site B, then site II, and lastly site
D. Assuming that sedimentation has occurred at a constant rate along the transect over the
past million years, rearrange the sites mentioned above on the basis of the thickness of the
sediments overlying the igneous rock, from thickest to thinnest.
A) A, B, II, D, III
B) I, II, III
C) III, II, D, B, A
D) III, A, II, B, D
E) III, D, II, B, A

E

An early consequence of the release of oxygen gas by plant and bacterial photosynthesis
was to
A) make life on land difficult for aerobic organisms.
B) change the atmosphere from oxidizing to reducing.
C) make it easier to maintain reduced molecules.
D) cause iron in ocean water and terrestrial rocks to rust (oxidize).
E) prevent the formation of an ozone layer.

D

Arrange these events from earliest to most recent.
1. emission of lava in what is now Siberia at time of Permian extinctions
2. emission of lava that solidified at the same time as iron-bearing terrestrial rocks began
to rust
3. emission of lava that solidified at the same time as rusted iron precipitated from
seawater
4. emission of lava in what is now India at time of Cretaceous extinctions
A) 3, 1, 2, 4
B) 3, 2, 1, 4
C) 3, 1, 4, 2
D) 1, 3, 2, 4
E) 1, 2, 3, 4

B

) Which free-living cells were the earliest contributors to the formation of Earthʹs oxidizing
atmosphere?
A) cyanobacteria
B) chloroplasts
C) mitochondria
D) seaweeds
E) endosymbionts

A

Which of the following statements provides the strongest evidence that prokaryotes
evolved before eukaryotes?
A) the primitive structure of plants
B) meteorites that have struck Earth
C) abiotic laboratory experiments that produced liposomes
D) Liposomes closely resemble prokaryotic cells.
E) The oldest fossilized cells resemble prokaryotes.

E

What is thought to be the correct sequence of these events, from earliest to most recent, in
the evolution of life on Earth?
1. origin of mitochondria
2. origin of multicellular eukaryotes
3. origin of chloroplasts
4. origin of cyanobacteria
5. origin of fungal-plant symbioses
A) 4, 3, 2, 1, 5
B) 4, 1, 2, 3, 5
C) 4, 1, 3, 2, 5
D) 4, 3, 1, 5, 2
E) 3, 4, 1, 2, 5

C

If it were possible to conduct sophisticated microscopic and chemical analyses of
microfossils found in 3.2-billion-year-old stromatolites, then within such microfossils, one
should be surprised to observe evidence of:
I. double-stranded DNA
II. a nuclear envelope
III. a nucleoid
IV. a nucleolus
V. nucleic acids
A) II only
B) III only
C) II and IV
D) II, III, and IV
E) all five of these

C

Recent evidence indicates that the first major diversification of multicellular eukaryotes
may have coincided in time with the
A) origin of prokaryotes.
B) switch to an oxidizing atmosphere.
C) melting that ended the ʺsnowball Earthʺ period.
D) origin of multicellular organisms.
E) massive eruptions of deep-sea vents.

C

Which of these observations fails to support the endosymbiotic theory for the origin of
eukaryotic cells?
A) the existence of structural and molecular differences between the plasma membranes
of prokaryotes and the internal membranes of mitochondria and chloroplasts
B) the existence of size differences between the cytosolic ribosomes of eukaryotes and
the ribosomes within mitochondria and chloroplasts
C) the existence of size differences between some prokaryotic cells and mitochondria
D) the existence of rRNA sequence differences between the cytosolic ribosomes of
eukaryotes and the ribosomes within mitochondria and chloroplasts

A

) Which event is nearest in time to the end of the period known as snowball Earth?
A) oxygenation of Earthʹs seas and atmosphere
B) evolution of mitochondria
C) Cambrian explosion
D) evolution of true multicellularity
E) Permian extinction

C

The snowball Earth hypothesis provides a possible explanation for the
A) diversification of animals during the late Proterozoic.
B) oxygenation of Earthʹs seas and atmosphere.
C) colonization of land by plants and fungi.
D) origin of O2-releasing photosynthesis.
E) existence of prokaryotes around hydrothermal vents on the ocean floor.

A

If two continental land masses converge and are united, then the collision should cause
A) a net loss of intertidal zone and coastal habitat.
B) the extinction of any species adapted to intertidal and coastal habitats.
C) an overall decrease in the surface area located in the continental interior.
D) a decrease in climatic extremes in the interior of the new super-continent.
E) the maintenance of the previously existing ocean currents and wind patterns.

A

A major evolutionary episode that corresponds in time most closely with the formation of
Pangaea was the
A) origin of humans.
B) Cambrian explosion.
C) Permian extinctions.
D) Pleistocene ice ages.
E) Cretaceous extinctions.

C

On the basis of their morphologies, how might Linnaeus have classified the Hawaiian
silverswords?
A) He would have placed them all in the same species.
B) He would have classified them the same way that modern botanists do.
C) He would have placed them in more species than modern botanists do.
D) He would have used evolutionary relatedness as the primary criterion for their
classification.
E) Both B and D are correct.

C

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 thin, moist skin without scales.
D) Its dentition (tooth pattern) was typical of modern mammals.
E) It would have had no temporal fenestra in its skull.

B

Which of Lystrosaurusʹ features help explain why these organisms fossilized so abundantly?
I. the presence of hard parts, such as tusks
II. its herbivorous diet
III. its persistence across at least two geological eras
IV. its widespread geographic distribution
V. its mixture of reptilian and mammalian features
A) I and III
B) III and V
C) III and V
D) I, III, and IV
E) II, III, IV, and V

D

Which of these is the most likely explanation for the modern-day distribution of
dicynodont fossils?
A) There had been two previous super-continents 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 able to swim long distances, up to thousands of kilometers.
E) The dicynodonts could survive for periods of months aboard ʺraftsʺ of vegetation,
which carried them far and wide, but not to the northern hemisphere.

C

) The observation that tusks were limited to males in several species, and were apparently
not used in food-gathering, is evidence that the tusks probably
A) were used by males during the sex act.
B) served as heat-dissipation structures.
C) are homologous to claws.
D) were insignificant to the survival and/or reproduction of dicynodonts.
E) were maintained as the result of sexual selection.

E

Which of these is the most likely explanation for the existence of dicynodont fossils on
modern-day Antarctica?
A) They arrived there aboard ʺraftsʺ of vegetation, and quickly adapted to the bitterly
cold climate.
B) Earthʹs polar regions were once so warm (especially immediately after the ʺsnowball
Earth periodʺ) that reptiles and mammal-like reptiles flourished there.
C) The landmass that is now the Antarctic continent was formerly located at a
more-northerly position, and was also united to other landmasses.
D) Dicynodonts originated on the island continent of Antarctica and went extinct as the
continent migrated to its current position at the South Pole.

C

Dicynodonts survived the Permian extinction and, therefore, existed during both the
A) Paleozoic and Mesozoic eras.
B) Proterozoic and Archaean eons.
C) Proterozoic and Phanerozoic eons.
D) Mesozoic and Cenozoic eras.
E) Carboniferous and Permian periods.

A

) There are at least a dozen known species in the extinct genus Lystrosaurus. If each species
was suited to a quite different environment, then this relatively large number of species is
likely due to
A) sexual selection.
B) adaptive radiation.
C) heterochrony.
D) polyploidy.
E) species selection.

B

0) The dicynodonts survived the mass extinction that was most closely correlated in time, if
not in cause, with
A) snowball Earth.
B) a large (10 km) meteor striking the Earth.
C) an intense period of sun-spot formation, with subsequent increase in solar radiation.
D) the formation of Pangaea and lava flows that covered large portions of Pangaea.
E) the pleistocene Ice Age.

D

The dicynodonts that survived the Permian extinction would initially have had to endure
(or escape from) the physical effects of __________, and subsequently, the biological effects
of __________.
A) warm temperatures, decreased metabolism
B) arid conditions, disease
C) meteorite shock waves, lack of food
D) increased sea level, lack of freshwater
E) volcanic ash in the atmosphere, increased predation

E

If an increase in dicynodont species diversity (i.e., 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) the evolution of humans.

B

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.

C

) The oxygen revolution changed Earthʹs environment dramatically. Which of the following
adaptations 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

A

Select the factor most likely to have caused the animals and plants of 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 55 million years ago.

E

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

B

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 to 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 in its regulation that altered the spatial
organization of body parts.
D) heterochrony.
E) gene duplication.

C

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 protobionts that use DNA to direct the polymerization of amino acids
E) abiotic synthesis of organic molecules

D

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) paedomorphosis.
C) exaptation.
D) adaptive radiation.
E) changes in the Hox gene expression

C