Download Ecologists are studying how genetic and environmental factors can

PROCTOR VERSION
1.5 A: Genetic Changes in Populations Quiz
1.
Ecologists are studying how genetic and environmental factors can affect the masses of adult
sunfish. The graph below and to the left shows the original size distribution for a population of
sunfish in a lake.
Northern pike fish, predators of sunfish, are introduced into the lake. The graph above and to the
right shows the size distribution for the population of sunfish in the same lake many years after
the introduction of northern pike.
Which statement about the effect that the introduction of the northern pike had on the sunfish
population is best supported by the data in the graphs?
(A) Gene frequencies in the sunfish population remained stable and the population size
decreased because the pike ate sunfish of all sizes, as shown by the even distribution of
sizes and the decreased number of individuals in the second graph.
Distractor Rationale:
This answer suggests the student may understand that the sunfish population decreased,
but does not understand that the trend in the graphs suggests that gene frequencies did
not remain stable because the graphs show that the size distribution shifted to include fewer
small sunfish after the introduction of the northern pike. The graphs show a shift in the size
distribution of the sunfish population to larger sunfish, which is due to a change in gene
frequencies, resulting from northern pike preying on smaller sunfish and reducing the
sunfish population size.
(B) Gene frequencies changed in the sunfish population, but the population size was unchanged
because the pike ate smaller sunfish and the larger sunfish survived to produce more
offspring, as shown by the constant number of individuals and the shift to larger masses in
the second graph.
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PROCTOR VERSION
1.5 A: Genetic Changes in Populations Quiz
Distractor Rationale:
This answer suggests the student may understand that sunfish gene frequencies changed
over time, but does not understand that the graphs show that the overall population size of
the sunfish decreased because there were fewer sunfish in each size group after the
introduction of the northern pike. The graphs show a shift in the size distribution of the
sunfish population to larger sunfish, which is due to a change in gene frequencies, resulting
from northern pike preying on smaller sunfish and reducing the sunfish population size.
(C) Population size decreased and gene frequencies changed in the sunfish population to favor
genes that produce larger sunfish because the pike were eating more of the smaller sunfish
in the population, as shown by the decreased number of individuals overall and the shift to
larger masses in the second graph.
Rationale:
This answer suggests the student understands that the trend in the graphs suggests that
there was a decrease in smaller fish in the sunfish population and that, over time, sunfish
gene frequencies shifted to favor large-size alleles. The student also understands that an
increase in the mean mass of the sunfish is evidence that would support the claim that there
was a shift in the size distribution of the sunfish population to larger sunfish due to a change
in gene frequencies.
(D) Population size decreased and gene frequencies changed to favor medium-sized sunfish
because the pike were eating only small and large sunfish, preventing the large sunfish from
producing more offspring, as shown by the increase in the number of medium-sized fish in
the second graph.
Distractor Rationale:
This answer suggests the student may understand that the sunfish population decreased
and that sunfish gene frequencies changed over time, but does not understand that the
trend in the graphs suggests that the shift in the sunfish gene frequencies favors large fish
(not medium-sized), because the graphs show that the size distribution shifted to include
fewer small sunfish after the introduction of the northern pike. The student may not
understand that the original size distribution showed that there had been a large number of
medium-sized sunfish in the population, so a shift in the size distribution of the sunfish
population to larger sunfish would still include a large number of medium-sized sunfish, but
fewer small sunfish.
Aligned to: LO 1.5 CA 1.5: Impact of Environment on Evolution
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PROCTOR VERSION
1.5 A: Genetic Changes in Populations Quiz
2.
Ecologists are studying the effect of soil quality on the growth of alder trees and have identified a
gene (R) in which trees with the recessive phenotype (rr) are better able to tolerate acidic soil.
The table below shows the numbers of trees and the phenotypes for the R gene (trees tolerant of
acidic soil and trees not tolerant of acidic soil) in a population of alder trees in a Canadian
woodland.
Which conclusion best explains what is happening to the alder tree population over time?
(A) The data show that the alder tree population is decreasing and that evolution is not
occurring, because the gene frequencies of the two alleles (R and r) remain unchanged.
Distractor Rationale:
This answer suggests the student may understand that the alder tree population is
decreasing, but does not understand that the gene frequencies did not remain the same
because the population with the dominant phenotype (not tolerant of acidic soil) decreased
and the number of trees with the recessive phenotype (tolerant of acidic soil) remains
unchanged.
(B) The data show that the alder tree population is decreasing and that evolution is occurring,
because evolution always occurs when population sizes become reduced.
Distractor Rationale:
This answer suggests the student may understand that the population is decreasing and that
evolutionary changes occur more rapidly in small populations, but does not understand
that the data show that there was an increase in the percentage of alder trees tolerant of
acidic soil (recessive phenotype), which corresponds with a change in the gene frequencies
of the two alleles (R and r), and that it is the change in gene frequencies in populations that
results in evolutionary change.
(C) The data show that the alder tree population is going through a genetic bottleneck (genetic
drift), because the population is small and the gene frequencies are rapidly changing due to
random events.
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PROCTOR VERSION
1.5 A: Genetic Changes in Populations Quiz
Distractor Rationale:
This answer suggests the student may understand that the decreasing population could
result in changes in gene frequencies through a genetic bottleneck, but does not
understand that there is no evidence to support a genetic bottleneck (genetic drift) and that
changes in gene frequencies produce evolutionary change. The data show that there was
an increase in the percentage of alder trees tolerant of acidic soil (recessive phenotype),
which corresponds with a change in the gene frequencies of the two alleles (R and r), and
that it is the change in gene frequencies in populations that results in evolutionary change.
(D) The data show that the alder tree population is evolving, because the phenotypes are
changing due to changes in the gene frequencies of the two alleles (R and r).
Rationale:
This answer suggests the student understands that the number of trees for each phenotype
in the population in 2010, relative to the population numbers in 1800, suggests that gene
frequencies are changing and that evolution is occurring, because a higher percentage of
the total population is now tolerant of acidic soil, and that this change in phenotypic variation
is a result of a change in the genetic makeup of the alder tree population over time.
Aligned to: LO 1.5 CA 1.5: Impact of Environment on Evolution
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PROCTOR VERSION
1.5 A: Genetic Changes in Populations Quiz
3.
Anolis is a small lizard that lives throughout the southeastern United States. The color of an
Anolis varies from light green to dark brown and is governed by four sets of alleles. Due to a fire,
an area where a population of Anolis live that was once covered with light-colored vegetation is
now mostly covered with dark soil.
Which graph most accurately shows the likely change in the pigmentation distribution in the
Anolis population after the fire?
(A)
Distractor Rationale:
This answer suggests the student may understand that the environmental change will cause
a shift in phenotypic distribution, but does not understand that this will result in a
distribution resembling one bell curve shifting toward darker pigmentation because
individuals with more pigmentation will have a better chance of surviving in the new
environment. The student may mistakenly assume that two discrete phenotypes will result,
but a distribution resembling two bell curves would only result if selective pressures favored
extremes and not intermediate phenotypes.
(B)
Rationale:
This answer suggests the student understands that the environmental change will favor
darker phenotypes because individuals with greater pigmentation will have the greatest
chance of survival and reproduction and that a pattern resembling a bell curve will result
because a continuous distribution of phenotypes is likely, due to the numerous combinations
of alleles that can occur to create many intermediate colors.
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PROCTOR VERSION
1.5 A: Genetic Changes in Populations Quiz
(C)
Distractor Rationale:
This answer suggests the student may understand that the environmental change will cause
a shift in phenotypic distribution, but does not understand that this will result in a pattern
resembling a single bell curve shifting toward darker pigmentation because individuals with
more pigmentation will survive, resulting in a continuous distribution of darker phenotypes
due to the numerous combinations of alleles that can occur to create many intermediate
colors. The student may not understand that phenotypes would most likely be in a
continuum, instead of discrete.
(D)
Distractor Rationale:
This answer suggests the student may understand that the environmental change will cause
a shift in phenotypic distribution, but does not understand that this will result in a
distribution resembling a single bell curve shifting toward darker pigmentation because
individuals with more pigmentation will survive, resulting in a continuous distribution of
darker phenotypes due to the numerous combinations of alleles that can occur to create
many intermediate colors. The student may mistakenly assume that discrete phenotypes
will be present, because he or she may not understand that phenotypes would most likely be
in a continuum due to the numerous combinations of alleles that can occur to create many
intermediate colors.
Aligned to: LO 1.5 CA 1.5: Impact of Environment on Evolution
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PROCTOR VERSION
1.5 A: Genetic Changes in Populations Quiz
4.
Increases in atmospheric carbon dioxide levels may be lowering the pH of oceans in a process
known as ocean acidification. Researchers set up an experiment to test whether a population of
algae that are normally harmed by a low pH could adapt to the acidification. Algae were exposed,
for a period of one year (about 500 generations), to different degrees of ocean acidification, as
shown in the table below.
To test for adaptation, the researchers then transferred the algae from phase 1 of the experiment
into environments with different CO2 levels, to examine how the algae from phase 1 performed
when exposed to varying CO2 levels. In phase 2, algae from each of the groups in phase 1 were
grown in current atmospheric conditions, and algae from groups B and C were grown in the same
conditions as in phase 1, alongside algae grown in current-atmosphere conditions during phase 1
(group A). The graphs below summarize the results for phase 2 of the experiment.
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PROCTOR VERSION
1.5 A: Genetic Changes in Populations Quiz
Based on the experiment, which conclusion best explains how algae may respond to increasing
levels of atmospheric carbon dioxide?
(A) The data show that algae have lower growth rates in acidified oceans, but that algae that are
exposed to increased levels of CO2 will be favored through natural selection and be better
adapted to lower pH than present-day algae.
Rationale:
This answer suggests the student understands that the algae show some evolutionary
change after a year of exposure to higher CO2 levels, because the trends shown in the
graphs indicate that algae grown in extreme acidification displayed a faster growth rate in
the extreme conditions than the algae grown in normal CO2 levels.
(B) The data show that algae that are exposed to high levels of CO2 are least fit and, therefore,
that these algae will be unable to adapt to extreme increases in CO2 but may be able to
handle less extreme changes in CO2 levels.
Distractor Rationale:
This answer suggests the student may understand that the algae grown in the higher CO2
levels were least fit under normal CO2 levels, but does not understand that these algae
had actually adapted through artificial selection to grow in those conditions, because the
algae grown in the higher CO2 levels thrived, in comparison to the algae grown in the
current CO2 levels, when exposed to high levels of CO2.
(C) The data show that algae are successful in adapting to changes in ocean pH if the changes
are slow and very gradual, as evolutionary changes require long periods of time.
Distractor Rationale:
This answer suggests the student may understand that large evolutionary change requires a
long period of time, but does not understand that the data suggest that significant changes
can occur within populations relatively quickly, because the algae exposed to higher CO2
levels showed a significant change after only one year.
(D) The data show that algae will be unable to respond to changes in ocean pH, because the
algae that were exposed to high CO2 levels for a year show a significant decrease in growth
rate.
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PROCTOR VERSION
1.5 A: Genetic Changes in Populations Quiz
Distractor Rationale:
This answer suggests the student may understand that all of the treated algae show
decreased growth rates in the high-CO2 environments, but does not understand that this is
not evidence that the algae will not be able to survive in the changed environment, because
algae exposed to higher levels of CO2 did adapt.
Aligned to: LO 1.5 CA 1.5: Impact of Environment on Evolution
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