AP Biology Study Guide

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Catastrophism, meaning the regular occurrence of geological or meteorological disturbances (catastrophes),
was Cuvierʹs attempt to explain the existence of
A) evolution.
B) the fossil record.
C) uniformitarianism.
D) the origin of new species.
E) natural selection.

B) the fossil record

Which of the events described below agrees with the idea of catastrophism?
A) The gradual uplift of the Himalayas by the collision of the Australian crustal plate with the Eurasian
crustal plate
B) The formation of the Grand Canyon by the Colorado River over millions of years
C) The gradual deposition of sediments many kilometers thick on the floors of seas and oceans
D) The sudden demise of the dinosaurs, and various other groups, by the impact of a large extraterrestrial
body with Earth
E) The development of the Galapagos Islands from underwater seamounts over millions of years

D) The sudden demise of the dinosaurs, and various other groups, by the impact of a large extraterrestrial
body with Earth

During a study session about evolution, one of your fellow students remarks, ʺThe giraffe stretched its neck
while reaching for higher leaves; its offspring inherited longer necks as a result.ʺ Which statement is most likely
to be helpful in correcting this studentʹs misconception?
A) Characteristics acquired during an organismʹs life are generally not passed on through genes.
B) Spontaneous mutations can result in the appearance of new traits.
C) Only favorable adaptations have survival value.
D) Disuse of an organ may lead to its eventual disappearance.
E) Overproduction of offspring leads to a struggle for survival.

A) Characteristics acquired during an organismʹs life are generally not passed on through genes.

Which stratum should contain the greatest proportion of extinct organisms?

D

If ʺxʺ indicates the location of fossils of two closely related species, then fossils of their most-recent common
ancestor are most likely to occur in which stratum?

C

Which of these naturalists synthesized a concept of natural selection independently of Darwin?
A) Charles Lyell
B) Gregor Mendel
C) Alfred Wallace
D) John Henslow
E) Thomas Malthus

C) Alfred Wallace

Charles Darwin was the first person to propose
A) that evolution occurs.
B) a mechanism for how evolution occurs.
C) that the Earth is older than a few thousand years.
D) a mechanism for evolution that was supported by evidence.
E) a way to use artificial selection as a means of domesticating plants and animals.

D) a mechanism for evolution that was supported by evidence.

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) more recently they shared a common ancestor.

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) individuals adapt to their environments and, thereby, evolve

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) Well-adapted individuals leave more offspring, and thus contribute more to the next generationʹs gene

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) A, B, and C

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) A and B only

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) ability of populations to undergo modification as they adapt to a particular environment.

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) More small-beaked birds dying than larger-beaked birds. The offspring produced in subsequent
generations have a higher percentage of birds with large beaks.

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) Genetic variation among individuals

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) Offspring of insects that are genetically resistant to the pesticide become more abundant as the
susceptible insects die off.

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) None of the individual insects should have possessed genomes that made them resistant to DDT.

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) Flipper of a cetacean

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) they should share fewer homologous structures than two more closely related organisms.

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) A and C only

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) Under particular circumstances that persisted for long periods, each of these structures presented greater
costs than benefits.

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) All organisms use essentially the same genetic code.

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) The appendix has a substantial amount of defensive lymphatic tissue.

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) B and C only

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) island forms and mainland forms descended from common ancestors.

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) Biogeography

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) an overarching explanation, supported by much evidence, for how populations change over time.

Which of these is a statement that Darwin would have rejected?
A) Environmental change plays a role in evolution.
B) The smallest entity that can evolve is an individual organism.
C) Individuals can acquire new characteristics as they respond to new environments or situations.
D) Inherited variation in a population is a necessary precondition for natural selection to operate.
E) Natural populations tend to produce more offspring than the environment can support.

B) The smallest entity that can evolve is an individual organism.

Which definition of evolution would have been most foreign to Charles Darwin during his lifetime?
A) change in gene frequency in gene pools
B) descent with modification
C) the gradual change of a populationʹs heritable traits over generations
D) populations becoming better adapted to their environments over the course of generations
E) the appearance of new varieties and new species with the passage of time

A) change in gene frequency in gene pools

About which of these did Darwin have a poor understanding?
A) that individuals in a population exhibit a good deal of variation
B) that much of the variation between individuals in a population is inherited
C) the factors that cause individuals in populations to struggle for survival
D) the sources of genetic variations among individuals
E) how a beneficial trait becomes more common in a population over the course of generations

D) the sources of genetic variations among individuals

If, on average, 46% of the loci in a speciesʹ gene pool are heterozygous, then the average homozygosity of the
species should be
A) 23%
B) 46%
C) 54%
D) 92%
E) There is not enough information to say

C) 54%

Which of these variables is likely to undergo the largest change in value as the result of a mutation that
introduces a brand-new allele into a populationʹs gene pool at a locus that had formerly been fixed?
A) Average heterozygosity
B) Nucleotide variability
C) Geographic variability
D) Average number of loci

A) Average heterozygosity

Which of these is the smallest unit upon which natural selection directly acts?
A) a speciesʹ gene frequency
B) a populationʹs gene frequency
C) an individualʹs genome
D) an individualʹs genotype
E) an individualʹs phenotype

E) an individualʹs phenotype

Which of these is the smallest unit that natural selection can change?
A) a speciesʹ gene frequency
B) a populationʹs gene frequency
C) an individualʹs genome
D) an individualʹs genotype
E) an individualʹs phenotype

B) a populationʹs gene frequency

Which of these evolutionary agents is most consistent at causing populations to become better suited to their
environments over the course of generations?
A) Mutation
B) Non-random mating
C) Gene flow
D) Natural selection
E) Genetic drift

D) Natural selection

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is
true?
A) Each bird evolved a deeper, stronger beak as the drought persisted.
B) Each bird developed a deeper, stronger beak as the drought persisted.
C) Each birdʹs survival was strongly influenced by the depth and strength of its beak as the drought
persisted.
D) Each bird that survived the drought produced only offspring with deeper, stronger beaks than seen in the
previous generation.
E) The frequency of the strong-beak alleles increased in each bird as the drought persisted.

C) Each birdʹs survival was strongly influenced by the depth and strength of its beak as the drought
persisted.

Each of the following has a better chance of influencing gene frequencies in small populations than in large
populations, but which one most consistently requires a small population as a precondition for its occurrence?
A) Mutation
B) Non-random mating
C) Genetic drift
D) Natural selection
E) Gene flow

C) Genetic drift

A trend toward the decrease in the size of plants on the slopes of mountains as altitudes increase is an example
of
A) a cline.
B) a bottleneck.
C) relative fitness.
D) genetic drift.
E) geographic variation.

A) a cline.

Which of these makes determining the evolutionary relatedness of different species based on the amino acid
sequence of homologous proteins generally less accurate than determinations of relatedness based on the
nucleotide sequences of homologous genes?
A) Silent mutations
B) Gene duplications
C) Translocation events that change gene sequences
D) Crossing-over
E) Independent assortment

A) Silent mutations

Which is a true statement concerning genetic variation?
A) It is created by the direct action of natural selection.
B) It arises in response to changes in the environment.
C) It must be present in a population before natural selection can act upon the population.
D) It tends to be reduced by the processes involved when diploid organisms produce gametes.
E) A population that has a higher average heterozygosity has less genetic variation than one with a larger
average heterozygosity.

C) It must be present in a population before natural selection can act upon the population.

What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait
(aa) has not changed over time?
A) The population is undergoing genetic drift.
B) The two phenotypes are about equally adaptive under laboratory conditions.
C) The genotype AA is lethal.
D) There has been a high rate of mutation of allele A to allele a.
E) There has been sexual selection favoring allele a.

B) The two phenotypes are about equally adaptive under laboratory conditions.

What is the estimated frequency of allele A in the gene pool?
A) 0.05
B) 0.25
C) 0.50
D) 0.75
E) 1.00

C) 0.50

What proportion of the population is probably heterozygous (Aa) for this trait?
A) 0.05
B) 0.25
C) 0.50
D) 0.75
E) 1.00

C) 0.50

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a
is 0.4. What is the percentage of the population that is homozygous for this allele?
A) 4
B) 16
C) 32
D) 36
E) 40

B) 16

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is
0.1. What is the percentage of the population that is heterozygous for this allele?
A) 90
B) 81
C) 49
D) 18
E) 10

D) 18

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is
0.2. What is the frequency of individuals with Aa genotype?
A) 0.20
B) 0.32
C) 0.42
D) 0.80
E) Genotype frequency cannot be determined from the information provided.

B) 0.32

Which of these is closest to the allele frequency in the founding population?
A) 0.1 a, 0.9 A
B) 0.2 a, 0.8 A
C) 0.5 a, 0.5 A
D) 0.8 a, 0.2 A
E) 0.4 a, 0.6 A

A) 0.1 a, 0.9 A

If one assumes that Hardy-Weinberg equilibrium applies to the population of colonists on this planet, about
how many people will have attached earlobes when the planetʹs population reaches 10,000?
A) 100
B) 400
C) 800
D) 1,000
E) 10,000

A) 100

If four of the original colonists died before they produced offspring, the ratios of genotypes could be quite
different in the subsequent generations. This would be an example of
A) diploidy.
B) gene flow.
C) genetic drift.
D) disruptive selection.
E) stabilizing selection.

C) genetic drift.

Over time, the movement of people on Earth has steadily increased. This has altered the course of human
evolution by increasing
A) non-random mating.
B) geographic isolation.
C) genetic drift.
D) mutations.
E) gene flow.

E) gene flow.

Gene flow is a concept best used to describe an exchange between
A) species.
B) males and females.
C) populations.
D) individuals.
E) chromosomes.

C) populations.

Natural selection is most nearly the same as
A) diploidy.
B) gene flow.
C) genetic drift.
D) non-random mating.
E) differential reproductive success.

E) differential reproductive success.

The Darwinian fitness of an individual is measured most directly by
A) the number of its offspring that survive to reproduce.
B) the number of ʺgood genesʺ it possesses.
C) the number of mates it attracts.
D) its physical strength.
E) how long it lives.

A) the number of its offspring that survive to reproduce.

When we say that an individual organism has a greater fitness than another individual, we specifically mean
that the organism
A) lives longer than others of its species.
B) competes for resources more successfully than others of its species.
C) mates more frequently than others of its species.
D) utilizes resources more efficiently than other species occupying similar niches.
E) leaves more viable offspring than others of its species.

E) leaves more viable offspring than others of its species.

Which of the following statements best summarizes evolution as it is viewed today?
A) It is goal-directed.
B) It represents the result of selection for acquired characteristics.
C) It is synonymous with the process of gene flow.
D) It is the descent of humans from the present-day great apes.
E) It is the differential survival and reproduction of the most-fit phenotypes.

E) It is the differential survival and reproduction of the most-fit phenotypes.

Which describes brightly colored peacocks mating more frequently than drab peacocks?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

E) sexual selection

Most Swiss starlings produce four to five eggs in each clutch. Those producing fewer or more than this have
reduced fitness. Which of the following terms best describes this?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

C) stabilizing selection

Fossil evidence indicates that horses have gradually increased in size over geologic time. Which of the
following terms best describes this?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

B) directional selection

The average birth weight for human babies is about 3 kg. Which of the following terms best describes this?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

C) stabilizing selection

A certain species of land snail exists as either a cream color or a solid brown color. Intermediate individuals are
relatively rare. Which of the following terms best describes this?
A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

D) disruptive selection

The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infantʹs diet lacks the amino
acid, phenylalanine. What maintains the presence of this harmful allele in a populationʹs gene pool?
A) heterozygote advantage
B) stabilizing selection
C) diploidy
D) balancing selection

C) diploidy

Mules are relatively long-lived and hardy organisms that cannot, generally speaking, perform successful
meiosis. Consequently, which statement about mules is true?
A) They have a relative evolutionary fitness of zero.
B) Their offspring have less genetic variation than the parents.
C) Mutations cannot occur in their genomes.
D) If crossing-over happens in mules, then it must be limited to prophase of mitosis.
E) When two mules interbreed, genetic recombination cannot occur by meiotic crossing over, but only by the
act of fertilization.

A) They have a relative evolutionary fitness of zero.

A proficient engineer can easily design skeletal structures that are more functional than those currently found
in the forelimbs of such diverse mammals as horses, whales, and bats. That the actual forelimbs of these
mammals do not seem to be optimally arranged is because
A) natural selection has not had sufficient time to create the optimal design in each case, but will do so given
enough time.
B) natural selection operates in ways that are beyond the capability of the human mind to comprehend.
C) in many cases, phenotype is not merely determined by genotype, but by the environment as well.
D) though we may not consider the fit between the current skeletal arrangements and their functions
excellent, we should not doubt that natural selection ultimately produces the best design.
E) natural selection is generally limited to modifying structures that were present in previous generations
and in previous species.

E) natural selection is generally limited to modifying structures that were present in previous generations
and in previous species.

Which of the following statements about species, as defined by the biological species concept, is (are) correct?
I. Biological species are defined by reproductive isolation.
II. Biological species are the model used for grouping extinct forms of life.
III. The biological species is the largest unit of population in which successful reproduction is possible.
A) I only
B) II only
C) I and III
D) II and III
E) I, II, and III

C) I and III

What is generally true of two very closely related species that have diverged from each other quite recently?
A) They shared a common ancestor recently in evolutionary time.
B) Genes are unable to pass from one speciesʹ gene pool to the otherʹs gene pool.
C) They are unable to produce hybrid offspring upon interbreeding.
D) Their reproductive isolation from each other is complete.

A) They shared a common ancestor recently in evolutionary time.

Which of the various species concepts distinguishes two species based on the degree of genetic exchange
between their gene pools?
A) phylogenetic
B) ecological
C) biological
D) morphological

C) biological

There is still some controversy among biologists about whether Neanderthals should be placed within the same
species as modern humans, or into a separate species of their own. Most DNA sequence data analyzed so far
indicate that there was probably little or no gene flow between Neanderthals and Homo sapiens. Which species
concept is most applicable in this example?
A) phylogenetic
B) ecological
C) morphological
D) biological

D) biological

A biologist discovers two populations of wolf spiders whose members appear identical. Members of one
population are found in the leaf litter deep within the woods. Members of the other population are found in the
grass at the edge of the woods. The biologist decides to designate the members of the two populations as two
separate species. Which species concept is this biologist most closely utilizing?
A) ecological
B) biological
C) morphological
D) phylogenetic

A) ecological

What was the species concept most used by Linnaeus?
A) biological
B) morphological
C) ecological
D) phylogenetic

B) morphological

You are confronted with a box of preserved grasshoppers of various species that are new to science and have
not been described. Your assignment is to separate them into species. There is no accompanying information as
to where or when they were collected. Which species concept will you have to use?
A) biological
B) phylogenetic
C) ecological
D) morphological

D) morphological

Dog breeders maintain the purity of breeds by keeping dogs of different breeds apart when they are fertile.
This kind of isolation is most similar to which of the following reproductive isolating mechanisms?
A) reduced hybrid fertility
B) hybrid breakdown
C) mechanical isolation
D) habitat isolation
E) gametic isolation

D) habitat isolation

Two species of frogs belonging to the same genus occasionally mate, but the offspring fail to develop and
hatch. What is the mechanism for keeping the two frog species separate?
A) the postzygotic barrier called hybrid inviability
B) the postzygotic barrier called hybrid breakdown
C) the prezygotic barrier called hybrid sterility
D) gametic isolation
E) adaptation

A) the postzygotic barrier called hybrid inviability

Theoretically, the production of sterile mules by interbreeding between female horses and male donkeys
should
A) result in the extinction of one of the two parental species.
B) cause convergent evolution.
C) strengthen postzygotic barriers between horses and donkeys.
D) weaken the intrinsic reproductive barriers between horses and donkeys.
E) eventually result in the formation of a single species from the two parental species.

C) strengthen postzygotic barriers between horses and donkeys.

The biological species concept is inadequate for grouping
A) plants.
B) parasites.
C) asexual organisms.
D) animals that migrate.
E) sympatric populations.

C) asexual organisms.

Which example below will most likely guarantee that two closely related species will persist only as distinct
biological species?
A) colonization of new habitats
B) convergent evolution
C) hybridization
D) geographic isolation from one another
E) reproductive isolation from one another

E) reproductive isolation from one another

Races of humans are unlikely to evolve extensive differences in the future for which of the following reasons?
I. The environment is unlikely to change.
II. Human evolution is complete.
III. The human races are incompletely isolated.
A) I only
B) III only
C) I and II only
D) II and III only
E) I, II, and III

B) III only

A defining characteristic of allopatric speciation is
A) the appearance of new species in the midst of old ones.
B) asexually reproducing populations.
C) geographic isolation.
D) artificial selection.
E) large populations.

C) geographic isolation.

A rapid method of speciation that has been important in the history of flowering plants is
A) genetic drift.
B) a mutation in the gene controlling the timing of flowering.
C) behavioral isolation.
D) polyploidy.

D) polyploidy.

Two closely related populations of mice have been separated for many generations by a river. Climatic change
causes the river to dry up, thereby bringing the mice populations back into contact in a zone of overlap. Which
of the following is not a possible outcome when they meet?
A) They interbreed freely and produce fertile hybrid offspring.
B) They no longer attempt to interbreed.
C) They interbreed in the region of overlap, producing an inferior hybrid. Subsequent interbreeding between
inferior hybrids produces progressively superior hybrids over several generations.
D) They remain separate in the extremes of their ranges but develop a persistent hybrid zone in the area of
overlap.
E) They interbreed in the region of overlap, but produce sterile offspring.

C) They interbreed in the region of overlap, producing an inferior hybrid. Subsequent interbreeding between

The difference between geographic isolation and habitat differentiation is the
A) relative locations of two populations as speciation occurs.
B) speed (tempo) at which two populations undergo speciation.
C) amount of genetic variation that occurs among two gene pools as speciation occurs.
D) identity of the phylogenetic kingdom or domain in which these phenomena occur.
E) the ploidy of the two populations as speciation occurs

A) relative locations of two populations as speciation occurs.

Among known plant species, which of these have been the two most commonly occurring phenomena leading
to the origin of new species?
1. allopatric speciation
2. sympatric speciation
3. sexual selection
4. polyploidy
A) 1 and 3
B) 1 and 4
C) 2 and 3
D) 2 and 4

D) 2 and 4

Beetle pollinators of a particular plant are attracted to its flowersʹ bright orange color. The beetles not only
pollinate the flowers, but they mate while inside of the flowers. A mutant version of the plant with red flowers
becomes more common with the passage of time. A particular variant of the beetle prefers the red flowers to
the orange flowers. Over time, these two beetle variants diverge from each other to such an extent that
interbreeding is no longer possible. What kind of speciation has occurred in this example, and what has driven
it?
A) allopatric speciation, ecological isolation
B) sympatric speciation, habitat differentiation
C) allopatric speciation, behavioral isolation
D) sympatric speciation, sexual selection
E) sympatric speciation, allopolyploidy

B) sympatric speciation, habitat differentiation

The phenomenon of fusion is likely to occur when, after a period of geographic isolation, two populations meet
again and
A) their chromosomes are no longer homologous enough to permit meiosis.
B) a constant number of viable, fertile hybrids is produced over the course of generations.
C) the hybrid zone is inhospitable to hybrid survival.
D) an increasing number of viable, fertile hybrids is produced over the course of generations
E) a decreasing number of viable, fertile hybrids is produced over the course of generations.

D) an increasing number of viable, fertile hybrids is produced over the course of generations

A hybrid zone is properly defined as
A) an area where two closely related speciesʹ ranges overlap.
B) an area where mating occurs between members of two closely related species, producing viable offspring.
C) a zone that features a gradual change in species composition where two neighboring ecosystems border
each other.
D) a zone that includes the intermediate portion of a cline.
E) an area where members of two closely related species intermingle, but experience no gene flow.

B) an area where mating occurs between members of two closely related species, producing viable offspring.

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, this is most likely to lead to
A) fusion.
B) reinforcement.
C) stability.
D) further speciation events.

B) reinforcement.

According to the concept of punctuated equilibrium, the ʺsuddenʺ appearance of a new species in the fossil
record means that
A) the species is now extinct.
B) speciation occurred instantaneously.
C) speciation occurred in one generation.
D) speciation occurred rapidly in geologic time.
E) the species will consequently have a relatively short existence, compared with other species.

D) speciation occurred rapidly in geologic time.

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 branch gradually into 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.
E) transitional fossils, intermediate between newer species and their parent species, should be abundant.

C) a new species accumulates most of its unique features as it comes into existence.

Which of the following would be a position held by an adherent of the punctuated equilibrium theory?
A) A new species forms most of its unique features as it comes into existence and then changes little for the
duration of its existence.
B) One should expect to find many transitional fossils left by organisms in the process of forming new
species.
C) Given enough time, most existing species will gradually evolve into new species.
D) Natural selection is unimportant as a mechanism of evolution.

A) A new species forms most of its unique features as it comes into existence and then changes little for the
duration of its existence.

Define 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 genetic change over vast expanses of time.
C) must begin with the geographic isolation of a small, frontier population.
D) proceeds at a uniform tempo across all taxa.
E) can involve changes involving a single gene.

E) can involve changes involving a single gene.

Which of the following statements about speciation is correct?
A) The goal of natural selection is speciation.
B) When reunited, two allopatric populations will not interbreed.
C) Natural selection chooses the reproductive barriers for populations.
D) Prezygotic reproductive barriers usually evolve before postzygotic barriers.
E) Speciation is a basis for understanding macroevolution.

E) Speciation is a basis for understanding macroevolution.

In order for speciation to occur, what is true?
A) The number of chromosomes in the genome must change.
B) Changes to centromere location or chromosome size must occur within the genome.
C) Large numbers of genes that affect a single phenotypic trait must change.
D) Large numbers of genes that affect numerous phenotypic traits must change.
E) At least one gene, affecting at least one phenotypic trait, must change.

E) At least one gene, affecting at least one phenotypic trait, must change.

Which gas was least abundant in Earth's early atmosphere, prior to 2 billion years ago?
A) O2
B) CO2
C) CH4
D) H2O
E) NH3

A) O2

Which of the following has not yet been synthesized in laboratory experiments studying the origin of life?
A) liposomes
B) liposomes with selectively permeable membranes
C) oligopeptides and other oligomers
D) protobionts that use DNA to program protein synthesis
E) amino acids

D) protobionts that use DNA to program protein synthesis

In what way were conditions on the early Earth of more than 3 billion years ago different from those on today's 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 Earth's early atmosphere.
E) Earth's early atmosphere had significant quantities of ozone.

B) Only early Earth was intensely bombarded by large space debris.

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) II, III, I, IV

Although absolute distinctions between the "most evolved" 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) perform controlled, precise reproduction.

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) DNA is chemically more stable and replicates with fewer errors (mutations) than RNA.

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) 22,400

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) only A and B

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) four

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) 3,500,000,000 years

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) It includes transitional forms with progressively specialized teeth.

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) cause iron in ocean water and terrestrial rocks to rust (oxidize).

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

A) cyanobacteria

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) The oldest fossilized cells resemble prokaryotes.

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 "snowball Earth" period.
D) origin of multicellular organisms.
E) massive eruptions of deep-sea vents.

C) melting that ended the "snowball Earth" period.

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

C) Cambrian explosion

The snowball Earth hypothesis provides a possible explanation for the
A) diversification of animals during the late Proterozoic.
B) oxygenation of Earth's 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) diversification of animals during the late Proterozoic.

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 net loss of intertidal zone and coastal habitat.

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) Permian extinctions.

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) were maintained as the result of sexual selection.

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) adaptive radiation.

An organism has a relatively large number of Hox genes in its genome. Which of the following is not true of this organism?
A) It evolved from evolutionary ancestors that had fewer Hox genes.
B) It must have multiple paired appendages along the length of its body.
C) It has the genetic potential to have a relatively complex anatomy.
D) At least some of its Hox genes owe their existence to gene duplication events.
E) Its Hox genes cooperated to produce the positional patterns of this organism as it developed.

B) It must have multiple paired appendages along the length of its body.

Bagworm moth caterpillars feed on evergreens and carry a silken case or bag around with them in which they eventually pupate. Adult female bagworm moths are larval in appearance; they lack the wings and other structures of the adult male and instead retain the appearance of a caterpillar even though they are sexually mature and can lay eggs within the bag. This is a good example of
A) allometric growth.
B) paedomorphosis.
C) sympatric speciation.
D) adaptive radiation.
E) changes in homeotic genes.

B) paedomorphosis.

As rat pups mature, the growth of their snouts and tails outpaces growth of the rest of their bodies, producing the appearance of sexually mature males. It is found that sexually mature female rats prefer to mate with mutant, sexually mature males that possess snouts and tails with juvenile proportions. Which of the following terms is (are) appropriately applied to this situation?
A) sexual selection
B) paedomorphosis
C) allometric growth
D) B and C only
E) A, B, and C

E) A, B, and C

A hypothetical mutation in a squirrel population produces organisms with eight legs rather than four. Further, these mutant squirrels survive, successfully invade new habitats, and eventually give rise to a new species. The initial event, giving rise to extra legs, would be a good example of
A) punctuated equilibrium.
B) species selection.
C) habitat selection.
D) changes in homeotic genes.
E) allometry.

D) changes in homeotic genes.

The existence of the phenomenon of exaptation is most closely associated with which of the following reasons that natural selection cannot fashion perfect organisms?
A) Natural selection and sexual selection can work at cross-purposes to each other.
B) Evolution is limited by historical constraints.
C) Adaptations are often compromises.
D) Chance events affect the evolutionary history of populations in environments that can change unpredictably.

B) Evolution is limited by historical constraints.

An explanation for the evolution of insect wings suggests that wings began as lateral extensions of the body that were used as heat dissipaters for thermoregulation. When they had become sufficiently large, these extensions became useful for gliding through the air, and selection later refined them as flight-producing wings. If this hypothesis is correct, insect wings could best be described as
A) adaptations.
B) mutations.
C) exaptations.
D) isolating mechanisms.
E) examples of natural selection's predictive ability.

C) exaptations.

If one organ is an exaptation of another organ, then what must be true of these two organs?
A) They are both vestigial organs.
B) They are homologous organs.
C) They are undergoing convergent evolution.
D) They are found together in the same hybrid species.
E) They have the same function.

B) They are homologous organs.

Many species of snakes lay eggs, but in the forests of northern Minnesota where growing seasons are short, only live-bearing snake species are present. This trend toward species that perform live birth is an example of
A) natural selection.
B) sexual selection.
C) species selection.
D) goal direction in evolution.
E) directed selection.

C) species selection.

In the 5—7 million years that the hominid lineage has been diverging from its common ancestor with the great apes, dozens of hominid species have arisen, often with several species coexisting in time and space. As recently as 30,000 years ago, Homo sapiens coexisted with Homo neanderthalensis. Both species had large brains and advanced intellects. The fact that these traits were common to both species is most easily explained by which of the following?
A) species selection
B) uniformitarianism
C) sexual selection
D) A and B only
E) A, B, and C

A) species selection

The existence of evolutionary trends, such as increasing body sizes among horse species, is evidence that
A) a larger volume-to-surface area ratio is beneficial to all mammals.
B) an unseen guiding force is at work.
C) evolution always tends toward increased complexity or increased size.
D) in particular environments, similar adaptations can be beneficial in more than one species.
E) evolution generally progresses toward some predetermined goal.

D) in particular environments, similar adaptations can be beneficial in more than one species.

Fossil evidence indicates that several kinds of flightless dinosaurs possessed feathers. If some of these feather-bearing dinosaurs incubated clutches of eggs in carefully constructed nests, this might be evidence supporting the claim that
A) dinosaurs were as fully endothermal (warm-blooded) as modern birds and mammals.
B) their feathers originally served as insulation, and only later became flight surfaces.
C) the earliest reptiles could fly, and the feathers of flightless dinosaurs were vestigial flight surfaces.
D) the feathers were plucked from the bodies of other adults to provide nest-building materials.
E) all fossils with feathers are actually some kind of bird.

B) their feathers originally served as insulation, and only later became flight surfaces.

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