In Darwinʹs thinking, the more closely related two different organisms are, the
A) more similar their habitats are.
B) less similar their DNA sequences are.
C) more recently they shared a common ancestor.
D) less likely they are to have the same genes in common.
E) more similar they are in size.

C

) Which of these conditions should completely prevent the occurrence of natural selection in
a population over time?
A) All variation between individuals is due only to environmental factors.
B) The environment is changing at a relatively slow rate.
C) The population size is large.
D) The population lives in a habitat where there are no competing species present

A

Natural selection is based on all of the following except
A) genetic variation exists within populations.
B) the best-adapted individuals tend to leave the most offspring.
C) individuals who survive longer tend to leave more offspring than those who die
young.
D) populations tend to produce more individuals than the environment can support.
E) individuals adapt to their environments and, thereby, evolve.

E

Which of the following represents an idea that Darwin learned from the writings of Thomas
Malthus?
A) All species are fixed in the form in which they are created.
B) Populations tend to increase at a faster rate than their food supply normally allows.
C) Earth changed over the years through a series of catastrophic upheavals.
D) The environment is responsible for natural selection.
E) Earth is more than 10,000 years old.

B

Which statement about natural selection is most correct?
A) Adaptations beneficial in one habitat should generally be beneficial in all other
habitats as well.
B) Different species that occupy the same habitat will adapt to that habitat by
undergoing the same genetic changes.
C) Adaptations beneficial at one time should generally be beneficial during all other
times as well.
D) Well-adapted individuals leave more offspring, and thus contribute more to the next
generationʹs gene pool, than do poorly adapted individuals.
E) Natural selection is the sole means by which populations can evolve.

D

Given a population that contains genetic variation, what is the correct sequence of the
following events, under the influence of natural selection?
1. Well-adapted individuals leave more offspring than do poorly adapted individuals.
2. A change occurs in the environment.
3. Genetic frequencies within the population change.
4. Poorly adapted individuals have decreased survivorship.
A) 2 → 4 → 1 → 3
B) 4 → 2 → 1 → 3
C) 4 → 1 → 2 → 3
D) 4 → 2 → 3 → 1
E) 2 → 4 → 3 → 1

A

A biologist studied a population of squirrels for 15 years. During that time, the population
was never fewer than 30 squirrels and never more than 45. Her data showed that over half
of the squirrels born did not survive to reproduce, because of competition for food and
predation. In a single generation, 90% of the squirrels that were born lived to reproduce,
and the population increased to 80. Which inference(s) about this population might be true?
A) The amount of available food may have increased.
B) The number of predators may have decreased.
C) The squirrels of subsequent generations should show greater levels of genetic
variation than previous generations, because squirrels that would not have survived
in the past will now survive.
D) A and B only
E) A, B, and C

E

To observe natural selectionʹs effects on a population, which of these must be true?
A) One must observe more than one generation of the population.
B) The population must contain genetic variation.
C) Members of the population must increase or decrease the use of some portion of their
anatomy.
D) A and C only
E) A and B only

E

If the HMS Beagle had completely bypassed the Galapagos Islands, Darwin would have had
a much poorer understanding of the
A) relative stability of a well-adapted populationʹs numbers over many generations.
B) ability of populations to undergo modification as they adapt to a particular
environment.
C) tendency of organisms to produce the exact number of offspring that the environment
can support.
D) unlimited resources that support population growth in most natural environments.
E) lack of genetic variation among all members of a population.

B

During drought years on the Galapagos, small, easily eaten seeds become rare, leaving
mostly large, hard-cased seeds that only birds with large beaks can eat. If a drought
persists for several years, what should one expect to result from natural selection?
A) Small birds gaining larger beaks by exercising their mouth parts.
B) Small birds mutating their beak genes with the result that later-generation offspring
have larger beaks.
C) Small birds anticipating the long drought and eating more to gain weight and,
consequently, growing larger beaks.
D) More small-beaked birds dying than larger-beaked birds. The offspring produced in
subsequent generations have a higher percentage of birds with large beaks.
E) Larger birds eating less so smaller birds can survive.

D

Which of the following statements is an inference of natural selection?
A) Subsequent generations of a population should have greater proportions of
individuals that possess traits better suited for success in unchanging environments.
B) An individual organism undergoes evolution over the course of its lifetime.
C) Habitats do not generally have unlimited resources.
D) Natural populations tend to reproduce to their full biological potential.
E) Some of the variation that exists among individuals in a population is genetic.

A

Which of the following must exist in a population before natural selection can act upon that
population?
A) Genetic variation among individuals
B) Variation among individuals caused by environmental factors
C) Sexual reproduction
D) B and C only
E) A, B, and C

A

) Which of Darwinʹs ideas had the strongest connection to Darwin having read Malthusʹs
essay on human population growth?
A) Descent with modification
B) Variation among individuals in a population
C) Struggle for existence
D) The ability of related species to be conceptualized in ʺtree thinkingʺ
E) That the ancestors of the Galapagos finches had come from the South American

C

How many separate species, both extant and extinct, are depicted in this tree?
A) 2
B) 3
C) 4
D) 5
E) 6

E

According to this tree, what percent of the species seem to be extant (i.e., not extinct)?
A) 25%
B) 33%
C) 50%
D) 66%
E) 75%

D

Which of the five common ancestors, labeled V—Z, has given rise to the greatest number of
species, both extant and extinct?
A) V
B) W
C) X
D) Y
E) Z

C

Which of the five common ancestors, labeled V—Z, has been least successful in terms of the
percent of its derived species that are extant?
A) V
B) W
C) X
D) Y
E) Z

B

Which of the five common ancestors, labeled V—Z, has been most successful in terms of the
percent of its derived species that are extant?
A) V
B) W
C) X
D) Y
E) Z

E

Which pair would probably have agreed with the process that is depicted by this tree?
A) Cuvier and Lamarck
B) Lamarck and Wallace
C) Aristotle and Lyell
D) Wallace and Linnaeus
E) Linnaeus and Lamarck

B

Evolutionary trees such as this are properly understood by scientists to be
A) theories.
B) hypotheses.
C) laws.
D) dogmas.
E) facts.

B

In a hypothetical environment, fishes called pike-cichlids are visual predators of
algae-eating fish (i.e., they locate their prey by sight). If a population of algae-eaters
experiences predation pressure from pike-cichlids, which of the following should least
likely be observed in the algae-eater population over the course of many generations?
A) Selection for drab coloration of the algae-eaters
B) Selection for nocturnal algae-eaters (active only at night)
C) Selection for larger female algae-eaters, bearing broods composed of more, and
larger, young
D) Selection for algae-eaters that become sexually mature at smaller overall body sizes
E) Selection for algae-eaters that are faster swimmers

C

Which statement best describes the evolution of pesticide resistance in a population of
insects?
A) Individual members of the population slowly adapt to the presence of the chemical by
striving to meet the new challenge.
B) All insects exposed to the insecticide begin to use a formerly silent gene to make a
new enzyme that breaks down the insecticide molecules.
C) Insects observe the behavior of other insects that survive pesticide application, and
adjust their own behaviors to copy those of the survivors.
D) Offspring of insects that are genetically resistant to the pesticide become more
abundant as the susceptible insects die off.

D

DDT was once considered a ʺsilver bulletʺ that would permanently eradicate insect pests.
Today, instead, DDT is largely useless against many insects. Which of these would have
been required for this pest eradication effort to be successful in the long run?
A) Larger doses of DDT should have been applied.
B) All habitats should have received applications of DDT at about the same time.
C) The frequency of DDT application should have been higher.
D) None of the individual insects should have possessed genomes that made them
resistant to DDT.
E) DDT application should have been continual.

D

Some members of a photosynthetic plant species are genetically resistant to an herbicide,
while other members of the same species are not resistant to the herbicide. Which
combination of events should cause the most effective replacement of the
non-herbicide-resistant strain of plants by the resistant strain?
1. The presence of the herbicide in the environment
2. The absence of the herbicide from the environment
3. The maintenance of the proper conditions for one generation
4. The maintenance of the proper conditions for many generations
A) 1 and 3
B) 1 and 4
C) 2 and 3
D) 2 and 4

B

C

) Of the following anatomical structures, which is homologous to the wing of a bird?
A) Dorsal fin of a shark
B) Hindlimb of a kangaroo
C) Wing of a butterfly
D) Tail fin of a flying fish
E) Flipper of a cetacean

E

If two modern organisms are distantly related in an evolutionary sense, then one should
expect that
A) they live in very different habitats.
B) they should share fewer homologous structures than two more closely related
organisms.
C) their chromosomes should be very similar.
D) they shared a common ancestor relatively recently.
E) they should be members of the same genus.

B

Structures as different as human arms, bat wings, and dolphin flippers contain many of the
same bones, these bones having developed from very similar embryonic tissues. How do
biologists interpret these similarities?
A) By identifying the bones as being homologous
B) By the principle of convergent evolution
C) By proposing that humans, bats, and dolphins share a common ancestor
D) A and C only
E) A, B, and C

D

Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms
have lost their digestive systems. Whales have lost their hind limbs. How can natural
selection account for these losses?
A) Natural selection cannot account for losses, only for innovations.
B) Natural selection accounts for these losses by the principle of use and disuse.
C) Under particular circumstances that persisted for long periods, each of these
structures presented greater costs than benefits.
D) The ancestors of these organisms experienced harmful mutations that forced them to
find new habitats that these species had not previously used.

C

Which of the following pieces of evidence most strongly supports the common origin of all
life on Earth?
A) All organisms require energy.
B) All organisms use essentially the same genetic code.
C) All organisms reproduce.
D) All organisms show heritable variation.
E) All organisms have undergone evolution.

B

Logically, which of these should cast the most doubt on the relationships depicted by an
evolutionary tree?
A) None of the organisms depicted by the tree ate the same foods.
B) Some of the organisms depicted by the tree had lived in different habitats.
C) The skeletal remains of the organisms depicted by the tree were incomplete (i.e., some
bones were missing).
D) Transitional fossils had not been found.
E) Relationships between DNA sequences among the species did not match relationships
between skeletal patterns.

E

Which of the following statements most detracts from the claim that the human appendix is
a completely vestigial organ?
A) The appendix can be surgically removed with no immediate ill effects.
B) The appendix might have been larger in fossil hominids.
C) The appendix has a substantial amount of defensive lymphatic tissue.
D) Individuals with a larger-than-average appendix leave fewer offspring than those
with a below-average-sized appendix.
E) In a million years, the human species might completely lack an appendix.

C

Members of two different species possess a similar-looking structure that they use in a
similar fashion to perform the same function. Which information would best help
distinguish between an explanation based on homology versus one based on convergent
evolution?
A) The two species live at great distance from each other.
B) The two species share many proteins in common, and the nucleotide sequences that
code for these proteins are almost identical.
C) The sizes of the structures in adult members of both species are similar in size.
D) Both species are well adapted to their particular environments.
E) Both species reproduce sexually.

B

Ichthyosaurs were aquatic dinosaurs. Fossils show us that they had dorsal fins and tails, as
do fish, even though their closest relatives were terrestrial reptiles that had neither dorsal
fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are
A) homologous.
B) examples of convergent evolution.
C) adaptations to a common environment.
D) A and C only
E) B and C only

E

) It has been observed that organisms on islands are different from, but closely related to,
similar forms found on the nearest continent. This is taken as evidence that
A) island forms and mainland forms descended from common ancestors.
B) common environments are inhabited by the same organisms.
C) the islands were originally part of the continent.
D) the island forms and mainland forms are converging.
E) island forms and mainland forms have identical gene pools.

A

Monkeys of South and Central America have prehensile tails, meaning that their tails can
be used to grasp objects. The tails of African and Asian monkeys are not prehensile. Which
discipline is most likely to provide an evolutionary explanation for how this difference in
tails came about?
A) Aerodynamics
B) Biogeography
C) Physiology
D) Biochemistry
E) Botany

B

The theory of evolution is most accurately described as
A) an educated guess about how species originate.
B) one possible explanation, among several scientific alternatives, about how species
have come into existence.
C) an opinion that some scientists hold about how living things change over time.
D) an overarching explanation, supported by much evidence, for how populations
change over time.
E) an idea about how acquired characteristics are passed on to subsequent generations.

D

Which of the following is not an observation or inference on which natural selection is
based?
A) There is heritable variation among individuals.
B) Poorly adapted individuals never produce offspring.
C) Species produce more offspring than the environment can support.
D) Individuals whose characteristics are best suited to the environment generally leave
more offspring than those whose characteristics are less suited.
E) Only a fraction of the offspring produced by an individual may survive.

B

The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the
corresponding bones in whales have very different shapes and proportions. However,
genetic data suggest that all three kinds of organisms diverged from a common ancestor at
about the same time. Which of the following is the most likely explanation for these data?
A) Humans and bats evolved by natural selection, and whales evolved by Lamarckian
mechanisms.
B) Forelimb evolution was adaptive in people and bats, but not in whales.
C) Natural selection in an aquatic environment resulted in significant changes to whale
forelimb anatomy.
D) Genes mutate faster in whales than in humans or bats.
E) Whales are not properly classified as mammals.

C

Which of the following observations helped Darwin shape his concept of descent with
modification?
A) Species diversity declines farther from the equator.
B) Fewer species live on islands than on the nearest continents.
C) Birds can be found on islands located farther from the mainland than the birdsʹ
maximum nonstop flight distance.
D) South American temperate plants are more similar to the tropical plants of South
America than to the temperate plants of Europe.
E) Earthquakes reshape life by causing mass extinctions.

D

Within a few weeks of treatment with the drug 3TC, a patientʹs HIV population consists
entirely of 3TC-resistant viruses. How can this result best be explained?
A) HIV can change its surface proteins and resist vaccines.
B) The patient must have become reinfected with 3TC-resistant viruses.
C) HIV began making drug-resistant versions of reverse transcriptase in response to the
drug.
D) A few drug-resistant viruses were present at the start of treatment, and natural
selection increased their frequency.
E) The drug caused the HIV RNA to change

D

DNA sequences in many human genes are very similar to the sequences of corresponding
genes in chimpanzees. The most likely explanation for this result is that
A) humans and chimpanzees share a relatively recent common ancestor.
B) humans evolved from chimpanzees.
C) chimpanzees evolved from humans.
D) convergent evolution led to the DNA similarities.
E) humans and chimpanzees are not closely related.

A

Which of the following pairs of structures is least likely to represent homology?
A) The wings of a bat and the arms of a human
B) The hemoglobin of a baboon and that of a gorilla
C) The mitochondria of a plant and those of an animal
D) The wings of a bird and those of an insect
E) The brain of a cat and that of a dog

D