Download Coloration in the scarlet tiger moth (Panaxia dominula) is found on a

PROCTOR VERSION
1.2 A: Natural Selection Quiz
1.
Coloration in the scarlet tiger moth (Panaxia dominula) is found on a single locus where two
alleles show incomplete dominance for pigment coloration. Data on 15,000 individual tiger moths
in a population were collected in 1965 and again in 2010. The data are shown in the table below.
Which statement best explains the data?
(A) The recessive allele frequency is increasing over time because of a selective pressure that
favors the heterozygous and recessive genotypes.
Rationale:
This answer suggests the student understands that the change in the allele frequencies is
likely due to a selective pressure acting on the population.
(B) The population is experiencing a change in allele frequencies because of a genetic mutation
that occurred during the time between the two population samplings.
Distractor Rationale:
This answer suggests the student may understand that genetic mutations can cause
changes in the allele frequencies, but does not understand that there is no evidence of a
genetic mutation in the data as both alleles were present in both samples.
(C) The distribution of phenotypes has changed rapidly over a short time period because the
population is evolving into a new species.
Distractor Rationale:
This answer suggests the student may understand that the population has experienced a
significant change in allele frequencies, but does not understand that a selective pressure
is acting on the population, which results in a change in the allele frequencies, and not
necessarily causing speciation within the population.
(D) The population is in genetic equilibrium because the white-spotted phenotype remains
dominant and the little spotting phenotype remains relatively rare.
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PROCTOR VERSION
1.2 A: Natural Selection Quiz
Distractor Rationale:
This answer suggests the student may understand that there are some fluctuations in the
allele frequencies in populations that are in genetic equilibrium, but does not understand
that the shift observed between the two samplings is greater than the normal fluctuations
seen in populations that are in equilibrium and suggests a shift in allele frequency due to a
selective pressure.
Aligned to: LO 1.2 CA 1.2: Evaluate Hardy-Weinberg Data
2.
A large population of cichlids, a freshwater fish, was introduced into an African lake.
Approximately 32% of the population was homozygous recessive for a certain trait. After twenty
generations of random mating, approximately 32% of the cichlids are still homozygous recessive
for the trait.
Which statement best explains why the frequency of the alleles in the cichlid population has
remained constant over time?
(A) Genetic drift could not occur in the cichlid population because no new individuals were
introduced into the lake to alter the gene pool.
Distractor Rationale:
This answer suggests the student may understand that genetic drift is a factor that can
produce change in a gene pool, but does not understand that genetic drift results from
random changes in the gene frequencies of a population over many generations and not
from the introduction of new individuals (gene flow).
(B) Most cichlids are heterozygous for the trait, and this ensures that the proportion of
individuals who are homozygous will not change over time.
Distractor Rationale:
This answer suggests the student may understand that favorable hybrid vigor (heterozygous
genotype) keeps the frequency of recessive alleles higher in a population, but does not
understand that keeping the frequency of recessive alleles high is not one of the conditions
necessary to keep a population in Hardy-Weinberg equilibrium.
(C) The rate of mutation in the cichlid population is very low and the genotypes in a population
will not change without frequent mutations.
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PROCTOR VERSION
1.2 A: Natural Selection Quiz
Distractor Rationale:
This answer suggests the student may understand that mutations can produce changes
within a gene pool, but does not understand that mutations are not the only factors that
change genotype frequencies, and that selective pressure (natural selection), genetic drift,
and gene flow can affect genotype frequencies.
(D) The two different phenotypes are equally adaptive in the lake environment, and this
suggests that there has been no selective pressure acting on genotypes.
Rationale:
This answer suggests the student understands that if no selective pressures are acting on
a large population, then allele frequencies will remain fairly constant if all other conditions for
Hardy-Weinberg equilibrium are met.
Aligned to: LO 1.2 CA 1.2: Evaluate Hardy-Weinberg Data
3.
Bettas, also known as Siamese fighting fish, are small tropical fish that inhabit lakes, rivers, and
oceans in Southeast Asia. Male bettas are extremely territorial and will attack other males who
enter their territory. During the breeding season, each male builds a nest to attract females. After
a female lays her eggs in the nest, the male fertilizes the eggs and guards them until they hatch.
The table below shows some data for four male bettas in a freshwater environment. The nests of
each male betta contained approximately the same number of eggs.
Based on the data in the table, which male betta had the greatest biological fitness?
(A) Betta W, because it defended the largest territory
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PROCTOR VERSION
1.2 A: Natural Selection Quiz
Distractor Rationale:
This answer suggests the student may understand that males that secure a large breeding
territory are likely to win more territorial battles against other males and be among the
strongest, but does not understand that biological fitness means the production of more
offspring, and this male did not produce the most offspring.
(B) Betta X, because it was the biggest and strongest
Distractor Rationale:
This answer suggests the student may understand that the most mass and length may make
a male stronger than other males, but does not understand that biological fitness means
the production of more offspring and not size or strength.
(C) Betta Y, because it had the longest lifespan
Distractor Rationale:
This answer suggests the student may understand that a longer lifespan can be an
indication of fitness, but does not understand that biological fitness means the greatest
production of and survival of more offspring.
(D) Betta Z, because it fertilized the most eggs
Rationale:
This answer suggests the student understands that biological fitness means how many
viable offspring are produced by an organism compared to others in the population.
Aligned to: LO 1.2 CA 1.2: Evaluate Hardy-Weinberg Data
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