Download Two species of chipmunk are being studied in a national park. The

PROCTOR VERSION
1.5 B: Variation and Fitness Quiz
1.
Two species of chipmunk are being studied in a national park. The alpine chipmunk lives on the
tops of mountain ranges, and the lodgepole chipmunk lives in lower forested areas. The historic
and modern ranges of the two species are shown in the maps below.
DNA samples from specimens preserved in 1910 and living individuals for both species are
tested. The results are shown in the table below.
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PROCTOR VERSION
1.5 B: Variation and Fitness Quiz
Which choice identifies the chipmunk species with the highest overall fitness and best explains
the difference in fitness observed in the two populations?
(A) The alpine chipmunk, because it has moved into a smaller area where the selective
pressures are similar, and therefore, a smaller set of alleles has been required for survival,
whereas the lodgepole chipmunk has maintained a large habitat with many niches, so
natural selection supports a wide variety of alleles
Distractor Rationale:
This answer suggests the student may understand that a large range promotes greater
genetic diversity, but does not understand that this explanation is not supported by the
data, because there is no evidence that a smaller range for the alpine chipmunk implies
fewer selective pressures on that population.
(B) The lodgepole chipmunk, because it has spread into the habitat originally held by the alpine
chipmunk, and this increased competition has reduced the number of available niches and
the population size of the alpine chipmunk, which has resulted in a loss of genetic diversity
Distractor Rationale:
This answer suggests the student may understand that competition from a new species can
cause population declines, but does not understand that this explanation is not supported
by the data, because the lodgepole chipmunk’s range has stayed relatively the same
according to the maps.
(C) The alpine chipmunk, because it had been competing with the lodgepole chipmunk for the
same resources due to the two species sharing the same fundamental niche, and through
this competition, the alpine chipmunk has adopted a smaller niche that requires less genetic
diversity than its original habitat
Distractor Rationale:
This answer suggests the student may understand that direct competition with another
species can reduce genetic diversity and population size, but does not understand that this
explanation is not supported by the data, because the evidence provided indicates that the
two chipmunks occupy different niches based on altitude.
(D) The lodgepole chipmunk, because the alpine chipmunk has suffered significant loss in
habitat, resulting in a smaller population size with less genetic diversity than the original
population, whereas the lodgepole chipmunk has maintained a relatively large population
and therefore retains a high genetic diversity
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PROCTOR VERSION
1.5 B: Variation and Fitness Quiz
Rationale:
This answer suggests the student understands that the maps show a major shift in the
habitat range of the alpine chipmunk and that this most likely indicates a decrease in both
population size and genetic diversity, and that, because the fitness of a population depends
on the diversity of the alleles present in the population and a smaller population will usually
have less genetic diversity, the alpine chipmunk would likely have a lower overall fitness
than the lodgepole chipmunk.
Aligned to: LO 1.5 CA 1.5: Impact of Environment on Evolution
2.
Polychlorinated biphenyls (PCBs) are toxic, man-made compounds found at high levels in some
rivers and bays in the United States. PCBs bind to a protein called AHR, which initiates the
transcription of genes in the nucleus and produces a toxic buildup of unnecessary proteins. In
rivers that have high levels of PCBs, some tomcod fish have been found to have a small deletion
in the gene that codes for the AHR protein; this deletion prevents PCBs from binding to the
protein. This mutation is high in tomcod populations that live in contaminated rivers, but is rare or
nonexistent in fish that live in other rivers.
The map below shows the relative frequency of the gene in different tomcod populations. The
white part of the pie chart for the tomcod population in each river or bay shows the proportion of
the population that has the gene deletion, and the black part of the pie chart shows the proportion
of the population that does not have the gene deletion.
Which statement describes the most likely outcome if tomcod with the deletion in the AHR gene
are introduced into other rivers in New England?
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PROCTOR VERSION
1.5 B: Variation and Fitness Quiz
(A) The gene frequency of the AHR mutation will remain low in all tomcod populations where the
tomcod with the mutation are introduced, because this mutation is only beneficial in the
Hudson and Hackensack Rivers, so there is no selective advantage to having the mutation
in other rivers.
Distractor Rationale:
This answer suggests the student may understand that the mutation is only beneficial in
rivers containing PCBs, such as the Hudson and Hackensack Rivers, but does not
understand that the mutation may also allow for a selective advantage in other rivers with
PCB contamination because the mutation would convey resistance to the toxic effects of
PCBs in these areas as well.
(B) The gene frequency of the AHR mutation will remain low in populations of tomcod fish where
there is no PCB contamination, but will become more prevalent in rivers that have PCB
contamination, because the populations of tomcod that contain the AHR mutation will have a
selective advantage.
Rationale:
This answer suggests the student understands that the AHR mutation frequency will
increase only in rivers with PCB contamination but will remain low in non-contaminated
rivers because there will be no selective advantage to having the AHR gene mutation.
(C) The gene frequency of the AHR mutation will increase in all tomcod populations where the
tomcod with the mutation are introduced, because the mutation allows fish to tolerate toxins,
such as PCBs, and therefore provides a selective advantage to tomcod that have the
mutation in the populations.
Distractor Rationale:
This answer suggests the student may understand that the mutation conveys a selective
advantage in PCB-contaminated rivers, but does not understand that the gene frequency
may not increase in non-contaminated rivers because this mutation may be selected against
in the absence of PCBs.
(D) The gene frequency of the AHR mutation will decrease and eventually disappear in all
tomcod populations where the tomcod with the mutation are introduced, because this
mutation is only beneficial in the Hudson and Hackensack Rivers and will be a disadvantage
in tomcod populations not found in these two rivers.
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PROCTOR VERSION
1.5 B: Variation and Fitness Quiz
Distractor Rationale:
This answer suggests the student may understand that the mutation is beneficial in the
Hudson and Hackensack Rivers, which contain PCBs, but does not understand that the
mutation may also allow for a selective advantage in other rivers with PCB contamination
because the mutation would convey resistance to the toxic effects of PCBs in these areas as
well.
Aligned to: LO 1.5 CA 1.5: Impact of Environment on Evolution
3.
There is variation in the size and brightness of the color of male peacocks’ tails. A peacock
population is observed in the wild, and the color and length of the male peacocks’ tails are noted.
The males are then tracked, and their percentages of total matings and their average life spans
are recorded. The data are shown below.
Based on the data, which is the best explanation of the evolutionary fitness of male peacocks?
(A) The male peacocks with long, more colorful tails are more fit because they are able to mate
with more females during their life spans.
Rationale:
This answer suggests the student understands that the data in the graph and table support
that male peacocks with long, colorful tails have a higher evolutionary fitness due to the
higher frequency of mating and despite the difference in average life span, because
reproductive success is the main component of evolutionary fitness, and that male peacocks
with long, colorful tails mate more frequently than male peacocks with short, less colorful
tails. The student is able to connect genotypic variation, differences in the length and color
of the male peacocks’ tails, with the different degrees of fitness.
Page 5 of 8
PROCTOR VERSION
1.5 B: Variation and Fitness Quiz
(B) The male peacocks with long, more colorful tails are more fit because they are healthier and
able to grow longer tails with brighter coloration.
Distractor Rationale:
This answer suggests the student may understand that producing long, brightly colored tail
feathers is a sign of health, but does not understand that fitness is ultimately about
reproductive success, and not just survival, because reproduction is what allows for the
passage of genes in the population.
(C) The male peacocks with short, less colorful tails are more fit because they have longer
average life spans.
Distractor Rationale:
This answer suggests the student may understand that survival is important in determining
fitness, but does not understand that fitness is ultimately about reproductive success, and
not just survival, because reproduction is what allows for the passage of genes in the
population.
(D) The male peacocks in the two groups have about the same level of fitness because the
males with long, more colorful tails have more reproductive success and the males with
short, less colorful tails have higher rates of survival.
Distractor Rationale:
This answer suggests the student may understand that survival and reproductive success
are both important, but does not understand that fitness is ultimately about reproductive
success, and not just survival, because reproduction is what allows for the passage of genes
in the population.
Aligned to: LO 1.5 CA 1.5: Impact of Environment on Evolution
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PROCTOR VERSION
1.5 B: Variation and Fitness Quiz
4.
In the 1990s, the Florida panther population had decreased to several dozen individuals, and
scientists predicted that the Florida panther would be extinct by 2015. In 1995, conservationists
introduced eight female panthers from Texas to the population. Between 1995 and 2003, the
Texas panthers bred with native Florida panthers, and now there are more than one hundred
panthers in South Florida. Before the introduction, biologists identified genetic markers of two
ancestral lines (descendants from a common relative). In 2007, genetic analysis revealed five
ancestral lines, as shown in the maps below.
Which statement best explains the changes in phenotypic variation and relative fitness of the
Florida panther population after the introduction of the Texas panthers?
(A) The phenotypes of the introduced panthers were better adapted to the environment than the
phenotypes of the Florida panthers, so the introduced genes replaced the original ancestral
genes because natural selection favored the introduced alleles.
Distractor Rationale:
This answer suggests the student may understand that when new alleles are introduced into
a population through gene flow, these alleles can increase in frequency if the alleles offer a
selective advantage, but does not understand that, in this case, the new alleles did not
completely overtake the existing alleles, but instead, they increased the relative fitness of
the existing population because the new alleles increased the genetic diversity in the
existing gene pool.
(B) The phenotypes of the introduced panthers were better adapted to the environment than the
phenotypes of the Florida panthers, so the introduced panthers started to drive the Florida
panthers to extinction because the panthers with the new alleles had a higher fitness.
Page 7 of 8
PROCTOR VERSION
1.5 B: Variation and Fitness Quiz
Distractor Rationale:
This answer suggests the student may understand that when new alleles are introduced into
a population through gene flow, these alleles can increase in frequency if the alleles offer a
selective advantage, but does not understand that, in this case, the new alleles did not
completely overtake the existing alleles and drive the original Florida panthers to extinction,
but instead, they increased the relative fitness of the existing population because the new
alleles increased the genetic diversity in the existing gene pool.
(C) The introduced panthers provided new alleles to the population, which increased the
evolutionary fitness of the Florida panther population because natural selection favored the
introduced alleles over the original ancestral genes.
Distractor Rationale:
This answer suggests the student may understand that new alleles were introduced into the
population and that these new alleles increased the relative fitness of the population, but
does not understand that this increased relative fitness is due to the additional genetic
diversity that the new alleles provided, not because natural selection necessarily favored the
introduced alleles over the original ancestral genes.
(D) The introduced panthers provided new alleles to the population, which increased the
evolutionary fitness of the Florida panther population because the new alleles increased
genetic diversity and phenotypic variation in the population.
Rationale:
This answer suggests the student understands that when the Texas panthers were
introduced into the population, they increased the relative fitness of the population because
they increased genetic diversity by introducing new alleles into a population with low genetic
diversity.
Aligned to: LO 1.5 CA 1.5: Impact of Environment on Evolution
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