Transcript Which of the following statements describe what all members of a
Which of the following statements describe what all members of a population share?
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2.
3.
4.
They are temporally isolated from each other.
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They are geographically isolated from each other.
They are members of the same species.
They have identical genes.
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All the genes of all members of a particular population make up the population’s 1. relative frequency.
2. phenotype.
3. genotype.
4. gene pool.
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2.
3.
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Which statement below about gene pools is typically true?
They contain two or more alleles for each inheritable trait.
They contain only dominant alleles.
They belong to two or more interbreeding species.
The relative frequencies of the alleles never change.
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If an allele makes up one fourth of a population’s alleles for a given trait, its relative frequency is 1. 100 percent.
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2. 75 percent.
3. 25 percent.
4. 4 percent.
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Interbreeding among members of a population results in
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3.
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different types of alleles in the gene pool.
changes in the relative frequencies of alleles in the gene pool.
no changes in the relative frequencies of alleles in the gene pool.
an absence of genetic variation in the population.
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In a population, the sum of the relative frequencies of all alleles for a particular trait is 1. equal to 100 percent.
2. equal to the number of alleles for the trait.
3. constantly changing.
4. dependent on the number of alleles.
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A change in a sequence of DNA is called a
1. recombination.
2. polygenic trait.
3. single-gene trait.
4. mutation.
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The two main sources of genetic variation are
1. genotypes and phenotypes.
2. gene shuffling and mutations.
3. single-gene traits and polygenic traits.
4. directional selection and disruptive selection.
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In many kinds of organisms, inheritable differences are due mostly to
1. mutations during gamete formation.
2. polygenic traits.
3. gene shuffling during gamete formation.
4. the effects of radiation.
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Gene shuffling includes the independent movement of chromosomes during meoisis as well as 1. mutations from radiation.
2. changes in the frequencies of alleles.
3. crossing-over.
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4. mutations from chemicals.
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In a particular population, sexual reproduction can produce
1. mutations.
2. many different phenotypes.
3. new allele frequencies.
4. meiosis.
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The gene shuffling that occurs as part of sexual reproduction
changes the gene pool’s allele frequencies.
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2. does not change the gene pool’s allele frequencies.
3. keeps the phenotypes consistent.
4. is caused by radiation or chemicals.
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A single-gene trait that has two alleles and that shows a simple dominant-recessive pattern will result in 1. one phenotype.
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2. two phenotypes.
3. four phenotypes.
4. millions of phenotypes.
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An example of a single-gene trait is
widow’s peak in humans.
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2. weight of human infants at birth.
3. height in humans.
4. beak size in the Galápagos finches.
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The number of phenotypes produced for a given trait depends upon
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the number of genes that control the trait.
which form of the trait is dominant.
the relative frequencies of the various alleles.
the relationship of allele frequencies to Mendelian ratios.
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The phenotypes for a typical polygenic trait can often be expressed as
1. a bar graph.
2. a bell-shaped curve.
3. Mendelian ratios.
4. allele frequencies.
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Compared to a polygenic trait, a single-gene trait tends to have
1. fewer phenotypes.
2. more phenotypes.
3. the same number of phenotypes.
4. phenotypes that form a bell shaped curve.
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A polygenic trait can have
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many possible genotypes, but few possible phenotypes.
many possible genotypes, producing many possible phenotypes.
fewer phenotypes than most single gene traits.
fewer genotypes than most single gene traits.
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Natural selection acts directly on
1. alleles.
2. genes.
3. phenotypes.
4. mutations.
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Which of the following is NOT a way in which natural selection affects the distribution of phenotypes?
1. directional selection
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2. stabilizing selection 3. disruptive selection 4. chance events
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When individuals at only one end of a bell curve of phenotype frequencies have high fitness, the result is 1. directional selection.
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2. stabilizing selection.
3. disruptive selection.
4. genetic drift.
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When individuals with an average form of a trait have the highest fitness, the result is 1. not predictable.
2. disruptive selection.
3. directional selection.
4. stabilizing selection.
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In a population of finches in which one group of birds has a short, parrotlike beak and another group has a long, narrow beak, what process has probably occurred?
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1. directional selection 2. disruptive selection 3. stabilizing selection 4. genetic drift
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If a mutation introduces a new skin color in a lizard population, which factor might determine whether the frequency of the new allele will increase?
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how many other alleles are present whether the mutation makes some lizards more fit for their environment than other lizards
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how many phenotypes the population has whether the mutation was caused by nature or by human intervention
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In genetic drift, allele frequencies change because of
1. mutations.
2. chance.
3. natural selection.
4. genetic equilibrium.
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Which of the following events do biologists consider a random change?
1. directional selection 2. speciation 3. disruptive selection 4. genetic drift
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Genetic drift tends to occur in populations that
1. are very large.
2. are small.
3. are formed from new species.
4. have unchanging allele frequencies.
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The type of genetic drift that follows the colonization of a new habitat by a small group of individuals is called 1. the Hardy-Weinberg principle.
2. the founder effect.
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3. directional selection.
4. stabilizing selection.
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One similarity between natural selection and genetic drift is that both events 1.
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are based completely on chance.
begin with one or more mutations.
involve a change in a population’s allele frequencies.
take place only in very small groups.
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The situation in which allele frequencies of a population remain constant is called 1. evolution.
2. genetic drift.
3. genetic equilibrium.
4. natural selection.
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One of the conditions required to maintain genetic equilibrium is
1. natural selection.
2. mutations.
3. nonrandom mating.
4. no movement into or out of the population.
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The genetic equilibrium of a population can be disturbed by each of the following EXCEPT 1. nonrandom mating.
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2. movement into and out of the population.
3. a large population size.
4. mutations.
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The allele frequencies of a population are more likely to remain unchanged if
1. the population size is reduced.
2. frequent movement into and out of the population occurs.
3. all mating is random.
4. the mutation rate increases.
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According to the Hardy-Weinberg principle, genetic equilibrium would be more likely in a population of mice if 1.
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the population size rapidly decreases.
mutation rates within the population rise.
no natural selection takes place.
there is frequent movement into and out of the population.
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Which factor would most likely disrupt genetic equilibrium in a large population?
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the production of large numbers of offspring mating that is not random the absence of movement into and out of the population the absence of mutations
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The separation of populations by barriers such as rivers, mountains, or bodies of water is called 1. temporal isolation.
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2. geographic isolation.
3. behavioral isolation.
4. genetic equilibrium.
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A factor that is necessary for the formation of a new species is
1. reproduction at different times.
2. geographic barriers.
3. different mating behaviors.
4. reproductive isolation.
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What situation might develop in a population having some plants whose flowers open at midday and other plants whose flowers open late in the day?
1. behavioral isolation 2. geographic isolation 3. temporal isolation 4. genetic drift
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The geographic isolation of two populations of a species tends to increase differences between their gene pools because it
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prevents interbreeding between the populations.
prevents interbreeding within each population.
causes temporal isolation of the two populations.
increases differences in courtship behavior.
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Although they often live in the same habitat, the American toad breeds earlier in the spring than the Fowler’s toad does. What can be inferred from this information?
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The two species do not interbreed because of geographic isolation.
The two species do not interbreed because of temporal isolation.
The two species interbreed throughout the spring season.
The American toad will cause the extinction of the Fowler’s toad.
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Which is the first step that occurred in the speciation of the Galápagos finches?
1. establishing genetic equilibrium 2. behavioral isolation 3. ecological competition 4. arrival of the founding population
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The Galápagos finch species are an excellent example of
1. speciation.
2. genetic equilibrium.
3. stabilizing selection.
4. selection on single-gene traits.
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2.
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What did Peter and Rosemary Grant learn about mate choice from the Galápagos finches?
Phenotype plays no role in mate choice.
Finches prefer mates with beaks similar in size to their own.
Finches prefer mates with smaller beaks than their own.
Finches prefer mates with larger beaks than their own.
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In Rosemary and Peter Grant’s study of the Galápagos finches, what process was encouraged by ecological competition during the dry season?
1. stabilizing selection 2. disruptive selection 3. directional selection 4. genetic drift
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Which statement about evolution in the Galápagos finches is true?
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Natural selection on beak size and shape is driven by available food.
Stabilizing selection has favored an intermediate beak type for all of the finches.
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Mate choice likely plays no role in the finches’ evolution.
None of the finch species is reproductively isolated.
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Because all members of a population can interbreed, biologists often study their genes as a single group. _________________________ 1. True 2. False
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In a gene pool, as the relative frequency of one allele for a trait increases, the relative frequencies of other alleles for that trait decrease. _________________________ 1. True 2. False
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Most inheritable differences are due to mutations that occur during the production of gametes. _________________________ 1. True
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2. False
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Mutations do not always affect an organism’s genotype—its physical, behavioral, and biochemical characteristics. _________________________ 1. True 2. False
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A polygenic trait is controlled by one gene. _________________________
1. True 2. False
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On a graph, the distribution of phenotypes for a single-gene trait tends to form a bell-shaped curve. _________________________ 1. True 2. False
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Natural selection on single-gene traits can lead to changes in allele frequencies. _________________________ 1. True
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2. False
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In a population of snakes with a range of body lengths, if the longest individuals have the highest fitness, disruptive selection is likely to occur. _________________________ 1. True 2. False
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In small populations, an allele can become more or less common simply by chance. _________________________ 1. True
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2. False
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Genetic drift may occur when a small group of individuals colonize a new habitat. _________________________ 1. True
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2. False
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When mutations introduce new alleles into a population, genetic variation is disrupted. _________________________ 1. True
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2. False
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In a population of birds, if females prefer males with long tails, the population violates the condition of directional selection described by the Hardy-Weinberg principle. _________________________ 1. True
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2. False
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In the type of reproductive isolation called behavioral isolation, two populations are separated by barriers such as rivers or mountains. _________________________ 1. True 2. False
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Two populations that have overlapping ranges can remain reproductively isolated through behavioral isolation or temporal isolation from each other. _________________________ 1. True
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2. False
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The first step of the speciation of the Galápagos finches likely was the arrival of founders from South America. _________________________ 1. True 2. False
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Participant Scores
Participant 1 Participant 2 Participant 3 Participant 4 Participant 5
A ____________________ is all genes present in a particular population.
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Crossing-over can occur during the meiotic divisions that produce cells called ____________________.
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Most inherited differences in the appearances of two brothers are due to the _________________________ that occurred during the production of gametes in their parents.
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The number of possible phenotypes for a given trait depends on how many ____________________ control the trait.
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A polygenic trait can have many possible genotypes and ____________________.
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For ____________________ traits, natural selection can affect the distribution of phenotypes in three different ways.
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The pattern of natural selection that acts most strongly against gray individuals in a population that ranges from black through gray to white is ____________________ selection.
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When the phenotypes of polygenic traits are represented by a bell curve, the ____________________ of individuals close together on the curve is not very different.
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In genetic drift, ____________________, not natural selection, plays a primary role in determining the number of descendants an organism has.
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According to the _________________________ principle, allele frequencies in a population will remain constant unless one or more of five specific factors cause those frequencies to change.
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When a population is NOT evolving, it is in a situation called _________________________.
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For new species to evolve, populations must be ____________________ isolated from each other.
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If two populations have been reproductively isolated and can no longer breed and produce fertile offspring, the process of _________________________ has occurred.
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In the Galápagos finches that Rosemary and Peter Grant studied, a pattern of natural selection called ____________________ selection favored individuals with larger, heavier beaks during a drought.
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In a particular environment, populations that are very different from each other are less likely to ____________________ with each other for resources.
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Are the members of a population necessarily the same species? Explain
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Explain how you could calculate the relative frequency of an allele in a gene pool.
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What are the two main sources of genetic variation? Which of them is more common?
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Would a trait that has only two distinct phenotypes more likely be a single-gene trait or a polygenic trait? How do you know?
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What does a bell-shaped curve showing the phenotypes for human height indicate about the relative number of very short and very tall people?
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Explain how stabilizing selection would affect a graph of the distribution of phenotypes for a trait.
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Is an allele for a trait that has no effect on a species’ fitness affected by natural selection? Explain
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Why might genetic drift occur if a small number of individuals colonize a new habitat?
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How does the size of a population affect the likelihood that its genetic crosses will produce the ratio of alleles predicted by the laws of probability?
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List the five conditions necessary to maintain genetic equilibrium in a population.
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Which population, one of nearly identical organisms or one of phenotypically varied organisms, would be more likely to remain in genetic equilibrium?
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Why might a geographic barrier such as a large river cause the formation of a new species of small rodents but not a new species of birds?
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What are three mechanisms for reproductive isolation? Which mechanism isolates two populations of similar frogs with different mating calls?
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How does the work of Peter and Rosemary Grant in the Galápagos relate to the work of Charles Darwin?
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What are the major steps that were likely involved in the speciation of the Galápagos finches?
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For a trait that has many different alleles, would an individual in the population be more likely to have that allele if it has a low relative frequency or a high relative frequency? Why?
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If the relative frequency of a single allele for a particular trait declines over time, what would happen to the relative frequencies of some or all other alleles for that trait? Explain
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Explain how shuffling a deck of playing cards can be a good model for the effect of sexual reproduction on the relative frequency of alleles in a population and the possible combinations of alleles.
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Define
mutation
and describe one situation in which a point mutation —the alteration of a single nucleotide—would affect an organism’s phenotype and another situation in which a point mutation would not affect phenotype.
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For a population, are the frequencies of phenotypes for a single-gene trait best expressed by a bar graph or a curve? Are the frequencies of phenotypes for a polygenic trait best expressed by a bar graph or a curve? Explain
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How are directional selection and disruptive selection similar? How are they different?
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Describe the founder effect, and describe the conditions in which it arises.
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The Hardy-Weinberg principle describes the conditions needed for the frequency of alleles in a population to remain unchanged. Explain why that stability occurs.
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Assume that a geographic barrier that results in two very different ecosystems splits a single population. What would likely happen to the two separate populations? Would this process occur more quickly, less quickly, or at the same rate as it would if the two populations lived in similar ecosystems?
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If each of the Galápagos Islands had contained an identical assortment and abundance of vegetation, would the impact of natural selection have been as pronounced as it was? Explain
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