Download Ecologists are studying how genetic and environmental factors can

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.
(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.
(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.
(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.
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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.
(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.
(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.
(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).
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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)
(B)
(C)
(D)
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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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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.
(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.
(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.
(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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