1.5 c: role of the environment in evolution quiz proctor ... · 1.5 c: role of the environment in...

1. Numbers of reported cases of bedbug infestations have been increasing over the past ten years

in the United States. In an attempt to combat the infestations, people began using pesticides to

kill the bedbugs, but now many bedbugs are resistant to the two most common pesticides.

The map below shows the percentages of bedbugs that are resistant to treatment in locations

across the United States. The different shades in the pie chart for a certain location show the

proportions of the population in that location that have mutations for resistance to one, both, or

neither of the pesticides.

1.5 C: Role of the Environment in Evolution Quiz

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Which statements best explain how the two strains of resistance may have occurred and

recommend the best course for future eradication of bedbugs?

(A) The continued use of pesticides by humans has allowed bedbugs to adapt to the pesticides

so that, if a bedbug survives an exposure, the bedbug will develop a resistance to the

pesticide. To combat this resistance, stronger pesticides must be used.

Distractor Rationale:

This answer suggests the student may understand that populations adapt to changes in their

environment, but does not understand that individuals do not adapt but either survive or do

not survive, and does not understand that increasing the concentration will probably select

for those individuals resistant to higher concentrations of pesticide. The student may not

recognize the role human actions play in the epidemic and how the overuse of pesticides

has contributed to the increased resistance in the bedbug population.

(B) When a bedbug population is almost eliminated by exposure to a pesticide, the bedbug

population experiences a genetic bottleneck (genetic drift) that results in the expression of

new genes. The new genes protect the survivors, so new bedbugs without the resistance

genes should be introduced into the bedbug population to weaken the population’s

resistance to the pesticides.


This answer suggests the student may understand that a genetic bottleneck (an event that

decreases the genetic diversity in a population due to a decrease in population size) often

results in changes in gene frequencies, but does not understand that a bottleneck only

removes genes from the gene pool, and does not understand that introducing non-resistant

bedbugs would not be effective since these bedbugs would be selected against during every

pesticide application. The student may not recognize the role human actions play in the

epidemic and how the overuse of pesticides has contributed to the increased resistance in

the bedbug population.

(C) The continued use of pesticides has selected for bedbugs that have some resistance to the

pesticide, and over time the resistance has been passed on to offspring and increased

within the population. To effectively deal with this resistance, different and new types of

pesticides must be used.


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PROCTOR VERSION

Rationale:

This answer suggests the student understands that repeated pesticide use is selecting for

pesticide resistance in the bedbug population, and that over time more bedbugs have

become resistant because survivors have passed on this resistance. The student also

understands that since all of the existing pesticides are similar in how they function,

development of different and new pesticides is required.

(D) The bedbug population can more effectively deal with low doses of various pesticides in the

environment and is becoming immune to the pesticides. In order to effectively kill all

bedbugs, one pesticide should be used at a time, and it should be used at a high

concentration.


This answer suggests the student may understand that low levels of pesticide use may allow

for survival of individuals with lower resistance, but does not understand that increasing

the concentration will probably select for those individuals resistant to higher concentrations

of pesticide. The student may not recognize the role human actions play in the epidemic

and how the overuse of pesticides has contributed to the increased resistance in the bedbug

population.

Aligned to: LO 1.5 CA 1.5: Impact of Environment on Evolution


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2. The Central European blackcap is a bird that spends its summers in Germany and historically

spent its winters in Spain. About 50 years ago, however, backyard bird feeding became popular

in Britain. With a ready supply of food in Britain, some blackcaps began to migrate northwest,

instead of southwest to Spain, and were able to survive and return to their summer breeding

grounds in Germany. (The birds begin their mating season soon after they arrive back in

Germany from their wintering grounds. Migration is an innate, genetically controlled behavior.)

Over time, the percentage of the population that migrates to Britain has increased. Today, about

10% of the population winters in Britain instead of Spain. The blackcap migratory routes are

shown in the map below.

The two populations of blackcaps have been studied, and the observations shown in the chart

below have been made. These differences have taken only 30 generations to appear.


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Which statements best explain the differences in phenotypes observed in the two blackcap

populations?

(A) The differences are due to the Britain-wintering blackcaps migrating to a new area and

interbreeding with other populations of blackcaps. This interbreeding introduces new alleles

into the population and changes the frequency of specific phenotypes in the area.


This answer suggests the student may understand that when new populations are

introduced, changes in allele frequency can lead to phenotypic changes, but does not

understand that interbreeding would probably not occur because the birds return to

Germany to breed.

(B) The differences are due to the Britain-wintering blackcaps migrating shorter distances and

having different food sources in their winter habitats. These changes are selecting for

different variations within the population and producing the changes observed.

Rationale:

This answer suggests the student understands that when birds take different migratory

routes, they encounter different selective forces that act unequally on different phenotypes in

the population and produce evolutionary change. Britain-wintering blackcaps show the

phenotypic traits of narrow, long beak and short, wide wing phenotypes because they

experience environmental factors, such as the different types of food in the wintering ground

and the short length of the migration route, that select for these specific phenotypes. Britain-

wintering blackcaps also arrive back in Germany and begin breeding before Spain-wintering

blackcaps, further isolating the two groups. The student is able to make the correlation

between specific environmental factors and the patterns in the Britain-wintering blackcap

phenotypes.

(C) The differences are due to the Spain-wintering blackcaps developing long wings and wide

beaks over their lifetimes, whereas the Britain-wintering blackcaps do not develop these

characteristics. The Spain-wintering blackcaps’ developed characteristics are passed

directly to the next generation and add up over many generations.


This answer suggests the student may understand that different selective pressures may

produce changes in populations, but does not understand that instead of individuals

passing characteristics developed during their lifetimes to the next generation, selective

pressures act on populations, because some individuals with advantageous traits have a

better chance of surviving and passing on those traits.


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(D) The differences are due to the small population size of the Britain-wintering blackcaps. This

small population has lost genetic diversity due to a genetic bottleneck, and as a result,

random changes have occurred in gene frequencies and population phenotypes.


This answer suggests the student may understand that small populations are subject to

random changes due to genetic drift, but does not understand that different migration

patterns and diets play significant roles in changes within populations, because these

selective pressures will act on the populations regardless of size.


3. The graph below shows variation in the pigmentation of a frog population living in a Central

American rain forest.

This frog species is one of many green frog species that live in the rain forest, but this species

displays a wider range of pigmentation phenotypes than most of the other green frog species. All

of the green frog species are preyed upon by snakes, birds, and small mammals. A mutation

occurs in this frog species that produces a toxic secretion from the skin, which does not hurt the

frog but makes the frog taste unpleasant to predators.

Which statement best predicts the likely change in pigmentation phenotype in the frog population

as this mutation becomes more prevalent?

(A) Because green pigmentation provides the best camouflage, there will be an increase in

green pigmentation and a decrease in yellow-green and blue-green pigmentation, since

these colors are easier to see in a rain forest environment.


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This answer suggests the student may understand that some phenotypes increase fitness

because they make individuals harder to see, but does not understand that an individual

that is toxic would have greater fitness if it also had warning coloration, since this would

allow predators to avoid it. The student may not recognize that predation and the presence

of other, non-toxic green frogs are the environmental factors in this scenario.

(B) Because female frogs find bright colors more attractive and the toxic secretions make

camouflage less important, there will be an increase in yellow-green and blue-green

pigmentation in the frog population.


This answer suggests the student may understand that some phenotypes increase fitness

because they increase reproductive success, but does not understand that, in this

environment, a phenotype that differs from that of other, non-toxic frog species will increase

fitness because increased survival will lead to increased reproductive success.

(C) Because toxic frogs with green pigmentation resemble other non-toxic green frogs, there will

be an increase in yellow-green and blue-green pigmentation, since these colors are easier

for predators to recognize and avoid.

Rationale:

This answer suggests the student understands that a toxic prey species has a greater

selective advantage if it has coloration that allows predators to recognize and avoid it.

Predators will begin to avoid the yellow-green and blue-green phenotypes of the toxic frog,

leading to an increase in the frequency of these two colors. Because the toxic green frogs

will not be readily distinguishable from the non-toxic green frogs, they will not be avoided by

predators and therefore will not increase in frequency.

(D) Because blue pigmentation is more commonly associated with toxic organisms than yellow

or green pigmentations are, there will be an increase in blue-green pigmentation and a

decrease in yellow-green and green pigmentation, as species with these phenotypes will be

mistaken for non-toxic species and will suffer higher rates of predation.


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This answer suggests the student may understand that blue pigmentation is commonly

associated with toxic or unpalatable species, but does not understand that any form of

recognizable warning coloration could provide for greater fitness for individuals with a

chemical defense, because the student may not recognize that predation and the presence

of other, non-toxic green frogs are the environmental factors in this scenario.


4. Biologists are studying how the unique environmental conditions found in Africa’s Lake Victoria

may affect the cichlid fish living in the lake. The cichlid fish are present in a wide diversity of

colors. Due to the presence of yellow-green phytoplankton and dissolved organic matter in Lake

Victoria, blue light dominates the visual environment at the surface, but in deep water, red light

dominates. Female cichlids prefer to mate with brightly colored males, and blue males will reflect

more blue light while red males reflect more red light, so there is a population of blue cichlids in

shallow water and a population of red cichlids in deep water.

Recent logging around the lake has caused the water to become cloudy with silt (pieces of fine

sand and clay), and now neither blue nor red light travels to significant depths in the lake.

Which statement predicts what is most likely to occur in the cichlid populations in Lake Victoria if

the cloudy water conditions persist for a long time?

(A) Because there is no longer a selective advantage to having red or blue coloration for males

at either depth, neither color will be favored at either depth, and the two populations will

begin to interbreed and lose their unique colorations.

Rationale:

This answer suggests the student understands that if the environment changes and no

longer offers a selective advantage to different-colored males at different locations, the

populations will begin to mate more randomly and the distinct red and blue phenotypes will

become less common because environmental factors will no longer be favoring the selection

of these specific phenotypes and they will decrease in frequency in the population.

(B) Because the water is cloudy with silt, brown-colored cichlids will be favored by the females

and will have a selective advantage in both populations.


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This answer suggests the student may understand that brown phenotypes might increase

fitness because they provide camouflage in the new conditions, but does not understand

that females would not change to favor brown phenotypes because they have been selected

to favor males with brighter colors.

(C) Because the water is cloudy and the fish cannot see through the silt, the fish will lose both

their coloration and their ability to see, since neither trait will be needed for their survival.


This answer suggests the student may understand that when an environment changes,

adaptations such as coloration or vision may be lost if they no longer provide a selective

advantage, but does not understand that there is no evidence in this case to support the

fish losing their vision or all of their coloration and that it is more likely that the distinct red

and blue phenotypes will become less common because environmental factors will no

longer be favoring the selection of these specific phenotypes and they will decrease in

frequency in the population.

(D) Because the females at the bottom of the lake favor red males and the females near the top

of the lake favor blue males, the populations will remain unchanged due to female

preference being genetically determined.


This answer suggests the student may understand that many behaviors, such as mate

selection, are genetically determined, but does not understand that there would not be a

selective advantage for males having either blue or red coloration in cloudy water because

the light would not favor either phenotype in the new conditions.



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