Download 1. In Darwin`s finches— a. occurrence of wet and dry years

1. In Darwin’s finches—
a. occurrence of wet and dry years preserves genetic variation for beak size
b. increasing beak size over time proves that beak size is inherited
c. large beak size is always favored
d. all of the above
The correct answer is a—occurrence of wet and dry years preserves genetic variation for
beak size
A. Answer a is correct. Selection in different years favors different phenotypes.
Assuming that there is a genetic basis to variation in beak size, this oscillating
selection will maintain variation through time.
The correct answer is a—
B. Answer b is incorrect. By itself, change in beak size over time cannot establish
that the trait is inherited. In Darwin’s finches the comparison between parent’s
and offspring’s beak size, especially in years when the environment of the parent
is different from that of the offspring, would be expected to be similar if the trait
was genetically based.
The correct answer is a—
C. Answer c is incorrect. In wet years small seeds are abundant enough that birds
with small beaks survive very well. Notice that beak size decreases in wet years.
The correct answer is a—
D. Answer d is incorrect. Only answer a is correct.
2. In the case of peppered moths, a parallel case in the United States—
a. is best considered as a coincidence
b. adds support to the industrial melanism hypothesis
c. demonstrates that birds don’t eat moths
d. none of these
The correct answer is b—
A. Answer a is incorrect. So many of the patterns between the two systems are the
same that it would be unlikely to represent a mere coincidence. In evolutionary
biology, this is frequently a means for establishing the strength of a particular
hypothesis
The correct answer is b—adds support to the industrial melanism hypothesis
B. Answer b is correct. So many of the details agree between two geographically
isolated systems that an alternative explanation would be hard to provide. For
example, in both regions the frequency of melanistic individuals increases with
increasing pollution, and then declines as pollution subsides.
The correct answer is b—
C. Answer c is incorrect. The parallel increase and decrease in frequency of
melanistic individuals in parallel with levels of pollution does not indicate why
this has occurred. Kettlewell’s hypothesis that predation by birds is responsible is
still being investigated.
The correct answer is b—
D. Answer d is incorrect. A correct answer is provided.
3. Artificial selection is different from natural selection because—
a. artificial selection is not capable of producing large changes
b. artificial selection does not require genetic variation
c. natural selection cannot produce new species
d. breeders (people) choose which individuals reproduce based on desirability of
traits
The correct answer is d—
A. Answer a is incorrect. As can be seen in the case of domesticated dogs, artificial
selection can produce very large differences that are often greater than the
differences seen between species in nature.
The correct answer is d—
B. Answer b is incorrect. Both natural selection and artificial selection require
variation among individuals that is genetically based. Otherwise, the traits of
organisms selected for breeding would not be expected in the offspring.
The correct answer is d—
C. Answer c is incorrect. Natural selection, working over very long periods of time
(generations), is capable of producing changes that eventually lead to the
generation of new species.
The correct answer is d—breeders (people) choose which individuals reproduce based on
desirability of traits
D. Answer d is correct. The only difference between artificial and natural selection is
that people replace the “environment” as the source of variation in survival and
reproduction.
4. Gaps in the fossil record—
a. demonstrate our inability to date geological sediments
b. are expected since the probability that any organism will fossilize is extremely
low
c. have not been filled in as new fossils have been discovered
d. weaken the theory of evolution
The correct answer is b—
A. Answer a is incorrect. Geological sediments can be aged both relatively (position)
and absolutely (by radioactive decay).
The correct answer is b—are expected since the probability that any organism will
fossilize is very low
B. Answer b is correct. Circumstances leading to the creation of a fossil are rare.
Most organisms that die decompose or are destroyed by scavengers. Moreover,
organisms without hard parts (for example, bone and an exoskeleton) are even
less likely to become fossilized.
The correct answer is b—
C. Answer c is incorrect. As more fossils are discovered, more and more “gaps” are
getting filled in. The best examples include modern birds and whales.
The correct answer is b—
D. Answer d is incorrect. Gaps do not threaten the theory of evolution; they are
expected, given the great diversity of extant species and what we know about the
process of fossilization. The study of work by biologists and paleontologists in
closing famous “gaps” is an excellent illustration of both the scientific process
and how robust the theory of evolution is.
5. Intermediate fossils illustrating the evolution of whales from their hoofed
ancestors include—
a. Pakicetus
b. Archaeopteryx
c. Equus
d. all of these
The correct answer is a—Pakicetus
A. Answer a is correct. The fossil of Pakicetus showed that it was a four-legged
mammal that may have lived on land, also spending time in the sea, but had
already evolved a whale-like skull.
The correct answer is a—
B. Answer b is incorrect. Archaeopteryx is an intermediate form between dinosaurs
and birds.
The correct answer is a—
C. Answer c is incorrect. Although Equus is a four-legged animal, it is the genus of
current and ancestral species of horses, not an ancestor of the whale.
The correct answer is a—
D. Answer d is incorrect. Only one answer is correct, answer a. Neither
Archaeopteryx nor Equus are ancestors of the whale. Archaeopteryx is believed
to be an intermediate form between dinosaurs and birds, not an ancestor of the
whale. Although Equus is a four-legged animal, it is the genus of current and
ancestral species of horses, not an ancestor of the whale.
Hint: Paleontologists continue to fill in the gaps in the fossil record. Although
many gaps interrupted the fossil record in Darwin's era, even then, scientists knew
of the Archaeopteryx fossil was transitional between dinosaurs and bird. Today
the fossil record is far more complete. For example, recently a four-legged
aquatic mammal, Pakicetus, was discovered that provides important insights
concerning the evolution of whales and dolphins from land-living, hoofed
ancestors.
6). The evolution of modern horses (Equus) is best described as—
a. the constant change and replacement of one species by another over time
b. a complex history of lineages that changed over time, with many going extinct
c. a simple history of lineages that have always resembled extant horses
d. none of these
The correct answer is b—
A. Answer a is incorrect. Even though species ancestral to horses were small and
lacked many characters of modern horses (for example, hooves), branches of the
horse evolutionary tree showed a mosaic of changes. For example, some lineages
had evolved specialized hoofs and teeth without necessarily showing large
increases in body size, and size actually decreased in some lineages.
The correct answer is b—a complex history of lineages that changed over time, with
many going extinct
B. Answer b is correct. The original view of a gradual change with species
replacement stemmed from the lack of a rich fossil collection for horses. As
paleontologists discovered more fossils, our view of the history of horses
changed. Horse evolution illustrates the evolutionary change is branching and
diversifying, and does not follow a linear path. This example shows both the
importance of fossils as a source of data, as well as how evolutionary hypotheses
are always subject to modification in light of new data.
The correct answer is b—
C. Answer c is incorrect. Horses have changed drastically over the last 50–30 million
years.
The correct answer is b—
D. Answer d is incorrect. Answer a is the correct answer.
7. Homologous structures—
a. are structures in two or more species that originate as the same structure in a
common ancestor
b. are structures that look the same in different species
c. cannot serve different functions in different species
d. must serve different functions in different species
The correct answer is a—are structures in two or more species that originate as the same
structure in a common ancestor
A. Answer a is correct. Homology is not necessarily a statement about function or
structure, although both properties can help identify homology, they do not define
it. The most important characteristic of homology is the idea that the same
characteristic can be identified in a common ancestor of the species in question.
The correct answer is a—
B. Answer b is incorrect. Structures that look the same are not necessarily
homologous. For example, the wing of a bat and a bird look similar—they are
both wings, after all. But wings were not present in the ancestor common to bats
and birds.
The correct answer is a—
C. Answer c is incorrect. The wing of a bird does not perform the same function as
the forelimb of a rat. In the first case (flight) the structure has a quite different
function from the second case (walking).
The correct answer is a—
D. Answer d is incorrect. As described in c, homologous structures may perform
similar or dissimilar functions. The forelimbs of bats and dogs are homologous
and perform the same function.
8. Convergent evolution
a. involves species that are closely related evolutionarily
b. depends on natural selection to produce similar phenotypic responses in
unrelated lineages
c. occurs only on islands
d. is expected when different lineages are exposed to vastly different selective
environments
The correct answer is b—
A. Answer a is incorrect. Convergence may and does occur among taxa that are not
closely related to one another. That is, the similarity does not come from descent
from a common ancestor with similar characteristics.
The correct answer is b—depends upon natural selection to produce similar phenotypic
responses in unrelated lineages
B. Answer b is correct. Only natural selection can make it likely that totally unrelated
organisms will come to resemble one another so closely. The effects of natural
selection come from the fact that the convergent taxa are exposed to very similar
environmental pressures.
The correct answer is b—
C. Answer c is incorrect. Although some of the most striking examples of
convergence come from island fauna and flora, it is not restricted to such habitats.
The correct answer is b—
D. Answer d is incorrect. The evolution of convergence must come from similarity of
the selective environment.
9. Convergent evolution—
a. occurs when natural selection produces similar characteristics in unrelated
species
b. is a weakness in evolutionary theory
c. is the best explanation for why there are gaps in the fossil record
d. always involves homologous characteristics
The correct answer is a—occurs when natural selection produces similar characteristics
in unrelated species
A. Answer a is correct. Convergent evolution by definition is unrelated species
adapting to a similar environments in comparable ways. For example, fastswimming marine organisms as diverse as sharks, tuna, and dolphins have all
evolved the same streamlined body form. Presumably, this results from natural
selection favoring a restricted set of “solutions” to common environmental
problems.
The correct answer is a—
B. Answer b is incorrect. Convergent evolution is consistent with evolutionary
theory. Indeed, one might expect convergence given that biological materials and
the laws of chemistry and physics apply constraints to the directions in which
evolution can act.
The correct answer is a—
C. Answer c is incorrect. Convergence has nothing to do with gaps in the fossil
record.
The correct answer is a—
D. Answer d is incorrect. Convergence may occur with characteristics that do not
have an origin in a common ancestor.
10. Which of the following represents valid criticism that weakens the theory of
evolution?
a. evolution violates the second law of thermodynamics
b. there are no fossil intermediates.
c. irreducible complexity of biological structures.
d. all of the above
e. none of the above
The correct answer is e—
A. Answer a is incorrect. The Second Law of Thermodynamics applies to closed
systems, which the Earth is not. The Earth is an open system that receives
continuous input of energy from the Sun. Biological systems use that energy to
create and maintain order.
The correct answer is e—
B. Answer b is incorrect. Since Darwin, many intermediates have been found in a
wide variety of taxa. Today, many well-studied transition species are known that
had not been discovered in Darwin’s time but which vastly strengthen his theory
of evolution.
The correct answer is e—
C. Answer c is incorrect. In every case where a biological character has been claimed
to be “irreducibly complex,” subsequent analysis has shown that to be false. Lack
of a detailed explanation of structure and function for every single complex
biological structure that exists does not mean that irreducibly complex structures
exist. Moreover, natural selection can lead to the evolution of characters that
today appear irreducibly complex because structures that previously were not
crucial to the functioning of the character can over time evolve to become
necessary.
The correct answer is e—
D. Answer d is incorrect. None of the previous answers are correct.
The correct answer is e—none of the above
E. Answer e is correct. None of the answers are correct.
11. Darwin’s finches are a noteworthy case study of evolution by natural selection
because evidence suggests—
a. they are descendants of many different species that colonized the Galápagos
b. they radiated from a single species that colonized the Galápagos
c. they are more closely related to mainland species than to one another
d. none of the above
The correct answer is b—
A. Answer a is incorrect. Although they resemble many different species that can be
found on the mainland, such as woodpeckers, tree finches, ground finches, and so
on, they diverged from a common finch ancestor that colonized the island.
The correct answer is b—they radiated from a single species that colonized the
Galápagos
B. Answer b is correct. The finch species and morphological divinity provides a clear
and powerful example of the strength of natural selection in producing
morphological diversity that can take advantage of various ecological
opportunities.
The correct answer is b—
C. Answer c is incorrect. Both molecular and genetic evidence argue the contrary.
The correct answer is b—
D. Answer d is incorrect. Answer b is the correct answer.
12. Vestigial structures—
a. are difficult to explain given evolutionary theory
b. always provide evidence of convergent evolution
c. can help establish patterns of common ancestry
d. must always severely affect negative survivorship or reproduction
The correct answer is c—
A. Answer a is incorrect. Vestigial structures usually have no effect (good or bad) on
an individual’s fitness; that is, they are inconsequential structures. As such, they
are not incompatible at all with evolutionary theory or the theory of natural
selection.
The correct answer is c—
B. Answer b is incorrect. The utility of structures is central to hypotheses of
convergent evolution. Vestigial structures, by definition, have lost their utility
and as such are unlikely to support hypotheses about evolutionary convergence.
The correct answer is c—can establish patterns of common ancestry
C. Answer c is correct because vestigial structures can often be identified as the
remnants of homologous features that can be used to infer evolutionary
relationships. For example, the vestiges of the hind limb bones and pelvic girdles
in some transitional species allowed biologists to more completely trace the
history of animals related to modern whales back to the early origins within
hoofed mammal ancestors.
The correct answer is c—
D. Answer d is incorrect. Vestigial structures persist due to their lack of function.
13. An example of convergent evolution is—
a. Australian marsupials and placental mammals
b. the flippers in fish, penguins, and dolphins
c. the wings in birds, bats, and insects
d. all of these
The correct answer is d—
A. Answer a is incorrect. Although the evolution of similar characteristics in
Australian marsupials and placental mammals provides many examples of
convergent evolution, this is not the only example provided.
The correct answer is d—
B. Answer b is incorrect. Although the development of flippers in fish, penguins, and
dolphins is an example of convergent evolution, this is not the only example
provided.
The correct answer is d—
C. Answer c is incorrect. Although the development of wings in birds, bats, and
insects is an example of convergent evolution, this is not the only example
provided.
The correct answer is d—all of these
D. Answer d is correct. Convergent evolution can be viewed as two different species
adapting to similar environments in similar ways. All of the examples listed
exhibit parallel evolutionary adaptations in similar environments.
Hint: Different geographical areas sometimes exhibit groups of plants and
animals of strikingly similar appearance, even though the organisms may be only
distantly related. It is difficult to explain so many similarities as the result of
coincidence. Instead, natural selection appears to have favored parallel
evolutionary adaptations in similar environments. Because selection in these
instances has tended to favor change that made the two groups more alike, their
phenotypes have converged. This form of evolutionary change is referred to as
convergent evolution.
14. Archaeopteryx—
a. is an intermediate form between extinct and extant horses
b. is an intermediate form between extinct and extant whales
c. is an intermediate form between dinosaurs and birds that is intermediate in all
its characteristics
d. shows a common pattern for intermediate forms of mixtures of some traits
resembling descendants and some traits resembling ancestors
The correct answer is d—
A. Answer a is incorrect. Archaeopteryx is not related to horses.
The correct answer is d—
B. Answer b is incorrect. Archaeopteryx is not related to whales.
The correct answer is d—
C. Answer c is incorrect. Archaeopteryx is not intermediate in all respects. Rather, it
is a mosaic, with some traits nearly identical to those of its dinosaur ancestors,
and others very similar to those of birds.
The correct answer is d—shows a common pattern for intermediate forms of mixtures of
some traits resembling descendants and some traits resembling ancestors
D. Answer d is correct. Like many fossil “intermediates,” Archaeopteryx is a mosaic
of ancestral and modern traits. Evolution does not proceed with all traits evolving
at the same rate, and so it is unreasonable to expect real organisms to appear as
smooth transitions between forms in all aspects of their characteristics.
15. The shape of the beaks of Darwin's finches, industrial melanism, and the changes
in horse teeth are all examples of—
a. artificial selection
b. natural selection
c. sympatric speciation
d. stabilizing selection
The correct answer is b—
A. Answer a is incorrect. Artificial selection is the process whereby humans impose
selection on plants and animals through selective mating to enhance
characteristics desirable for human uses. Artificial selection has produced
substantial change in the phenotypes of organisms throughout human history.
The changes, which occurred in Darwin’s finches, moths, and horse teeth, were
not controlled by human intervention, rather by natural alterations of their
environments.
The correct answer is b—natural selection
B. Answer b is correct. Natural selection is the selection of specific traits in
organisms over time based on the contributions of those traits to survival. If those
traits have a genetic basis, then evolutionary change will occur. The shape of the
beaks of Darwin's finches, the coloration of moths in industrialized areas, and the
changes in horse teeth were all traits selected for by changes in the organism's
environment.
The correct answer is b—
C. Answer c is incorrect. Sympatric speciation is the process by which one ancestral
species diverges into two species in sympatry. The role of sympatric speciation is
still debated, and no strong evidence suggests that it occurs in horses or Darwin’s
finches. Moreover, industrial melanism refers to change within a species.
The correct answer is b—
D. Answer d is incorrect. Stabilizing selection refers to the situation in which natural
selection favors the intermediate phenotype in a population. Evolutionary change
in horses, Darwin’s finches, and peppered moths was the result of directional
selection that favors individuals with extreme phenotypes.
Challenge Questions
1. What are the conditions necessary for evolution by natural selection?
Answer—Briefly, they are:
A. There must be variation among individuals within a population.
B. Variation among individuals must be related to differences among individuals in
their success in producing offspring over their lifetime.
C. Variation related to lifetime reproductive success must have a genetic (heritable)
basis.
Refer to Figure 21.2 for the following two questions.
2. Explain how data shown in Figure 21.2a and b relate to the conditions identified by
you in question 1.
Answer—Figure 21.2a shows in an indirect way that beak depth varies from year to year.
Presumably this is a function of variation among individuals in beak size. However, the
most important point of 21.2a is that it shows the result of selection. That is, if the three
conditions hold, we might expect to see average beak depth change accordingly as
precipitation varies from year to year. Figure 21.2b is more directly relevant to the
conditions noted for natural selection to occur. The figure shows that beak size varies
among individuals, and that it tends to be inherited.
3. On Figure 21.2b, draw the relationship between offspring beak depth and parent
beak depth, assuming that there is no genetic basis to beak depth in the medium
ground finch.
Answer—The relationship would be given by a cloud of points with no obvious linear
trend in any direction different from a zero slope. In other words, it would be a
horizontal line through an approximately circular cloud of points. Such data would
suggest that whether a parent(s) has a large or small beak has no bearing on the beak size
of its offspring.
4. Refer to Figure 21.5, artificial selection in the laboratory. In this experiment, one
population of Drosophila was selected for low numbers of bristles and the other
for high numbers. Note that not only did the means of the populations change
greatly in 35 generations, but also all individuals in both experimental populations
lie outside the range of the initial population.
What would happen if, within a population, both small and large individuals
were allowed to breed, but middle-sized ones were not?
Answer—Assuming that small and large individuals would breed with each other, then
middle-sized offspring would still be born (the result of matings between small and large
flies). Nonetheless, there would also be many small and large individuals (the result of
small x small and large x large matings). Thus, the frequency distribution of body sizes
would be much broader than the distributions in the figures. In some experiments,
reproductive isolation evolves in which small and large individuals evolve mating
preferences that prevent them from interbreeding, leading to the production of two
different-sized species. This would be a laboratory example of sympatric speciation.
Most studies, however, have failed to produce such reproductive isolation; rather, a single
population remains through time with great variation.