Ch 16 - Evolution of Population (Value 45)

Name:

Multiple Choice (Value 30)
Identify the choice that best completes the statement or answers the question.

All the genes of all members of a particular population make up the population’s

a.	relative frequency.	c.	genotype.
b.	phenotype.	d.	gene pool.

If an allele makes up one fourth of a population’s alleles for a given trait, its relative frequency is

a.	100 percent.	c.	25 percent.
b.	75 percent.	d.	4 percent.

Interbreeding among members of a population results in

a.	different types of alleles in the gene pool.
b.	changes in the relative frequencies of alleles in the gene pool.
c.	no changes in the relative frequencies of alleles in the gene pool.
d.	an absence of genetic variation in the population.

In a population, the sum of the relative frequencies of all alleles for a particular trait is

a.	equal to 100 percent.
b.	equal to the number of alleles for the trait.
c.	constantly changing.
d.	dependent on the number of alleles.

A change in a sequence of DNA is called a

a.	recombination.	c.	single-gene trait.
b.	polygenic trait.	d.	mutation.

The two main sources of genetic variation are

a.	genotypes and phenotypes.
b.	gene shuffling and mutations.
c.	single-gene traits and polygenic traits.
d.	directional selection and disruptive selection.

In organisms that reproduce sexually, inheritable variation is due mostly to

a.	mutations during gamete formation.
b.	polygenic traits.
c.	gene shuffling during gamete formation.
d.	the effects of radiation.

In a particular population, sexual reproduction can produce

a.	mutations.	c.	new allele frequencies.
b.	many different phenotypes.	d.	meiosis.

The gene shuffling that occurs as part of sexual reproduction

a.	changes the gene pool’s allele frequencies.
b.	does not change the gene pool’s allele frequencies.
c.	keeps the phenotypes consistent.
d.	is caused by radiation or chemicals.

10.

A single-gene trait that has two alleles and that shows a simple dominant-recessive pattern will result in

a.	one phenotype.	c.	four phenotypes.
b.	two phenotypes.	d.	millions of phenotypes.

11.

An example of a single-gene trait is

a.	widow’s peak in humans.	c.	height in humans.
b.	weight of human infants at birth.	d.	beak size in the Galápagos finches.

12.

The number of phenotypes produced for a given trait depends upon

a.	the number of genes that control the trait.
b.	which form of the trait is dominant.
c.	the relative frequencies of the various alleles.
d.	the relationship of allele frequencies to Mendelian ratios.

13.

The phenotypes for a typical polygenic trait can often be expressed as

a.	a bar graph.	c.	Mendelian ratios.
b.	a bell-shaped curve.	d.	allele frequencies.

14.

A polygenic trait can have

a.	many possible genotypes, but few possible phenotypes.
b.	many possible genotypes, producing many possible phenotypes.
c.	fewer phenotypes than most single-gene traits.
d.	fewer genotypes than most single-gene traits.

15.

Natural selection acts directly on

a.	alleles.	c.	individual organisms.
b.	genes.	d.	mutations.

16.

Which of the following is NOT a way in which natural selection affects the distribution of phenotypes?

a.	directional selection	c.	disruptive selection
b.	stabilizing selection	d.	chance events

17.

When individuals at only one end of a bell curve of phenotype frequencies have high fitness, the result is

a.	directional selection.	c.	disruptive selection.
b.	stabilizing selection.	d.	genetic drift.

18.

When individuals with an average form of a trait have the highest fitness, the result is

a.	not predictable.	c.	directional selection.
b.	disruptive selection.	d.	stabilizing selection.

19.

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?

a.	how many other alleles are present
b.	whether the mutation makes some lizards more fit for their environment than other lizards
c.	how many phenotypes the population has
d.	whether the mutation was caused by nature or by human intervention

20.

Genetic drift tends to occur in populations that

a.	are very large.	c.	are formed from new species.
b.	are small.	d.	have unchanging allele frequencies.

21.

The type of genetic drift that follows the colonization of a new habitat by a small group of individuals is called

a.	the Hardy-Weinberg principle.	c.	directional selection.
b.	the founder effect.	d.	stabilizing selection.

22.

One similarity between natural selection and genetic drift is that both events

a.	are based completely on chance.
b.	begin with one or more mutations.
c.	involve a change in a population’s allele frequencies.
d.	take place only in very small groups.

23.

One of the conditions required to maintain genetic equilibrium is

a.	natural selection.
b.	mutations.
c.	nonrandom mating.
d.	no movement into or out of the population.

24.

The genetic equilibrium of a population can be disturbed by each of the following EXCEPT

a.	nonrandom mating.
b.	movement into and out of the population.
c.	a large population size.
d.	mutations.

25.

The allele frequencies of a population are more likely to remain unchanged if

a.	the population size is reduced.
b.	frequent movement into and out of the population occurs.
c.	all mating is random.
d.	the mutation rate increases.

26.

According to the Hardy-Weinberg principle, genetic equilibrium would be more likely in a population of mice if

a.	the population size rapidly decreases.
b.	mutation rates within the population rise.
c.	no natural selection takes place.
d.	there is frequent movement into and out of the population.

27.

Which factor would most likely disrupt genetic equilibrium in a large population?

a.	the production of large numbers of offspring
b.	mating that is not random
c.	the absence of movement into and out of the population
d.	the absence of mutations

28.

The separation of populations by barriers such as rivers, mountains, or bodies of water is called

a.	temporal isolation.	c.	behavioral isolation.
b.	geographic isolation.	d.	genetic equilibrium.

29.

A factor that is necessary for the formation of a new species is

a.	reproduction at different times.	c.	different mating behaviors.
b.	geographic barriers.	d.	reproductive isolation.

30.

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?

a.	behavioral isolation	c.	temporal isolation
b.	geographic isolation	d.	genetic drift

31.

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?

a.	The two species do not interbreed because of geographic isolation.
b.	The two species do not interbreed because of temporal isolation.
c.	The two species interbreed throughout the spring season.
d.	The American toad will cause the extinction of the Fowler’s toad.

32.

Which is the first step that occurred in the speciation of the Galápagos finches?

a.	establishing genetic equilibrium	c.	ecological competition
b.	behavioral isolation	d.	arrival of the founding population

33.

The Galápagos finch species are an excellent example of

a.	speciation.	c.	stabilizing selection.
b.	genetic equilibrium.	d.	selection on single-gene traits.

34.

In Rosemary and Peter Grant’s study of the Galápagos finches, what process was encouraged by ecological competition during the dry season?

a.	stabilizing selection	c.	directional selection
b.	reproductive isolation	d.	genetic drift

35.

Which statement about evolution in the Galápagos finches is true?

a.	Natural selection on beak size and shape is driven by available food.
b.	Stabilizing selection has favored an intermediate beak type for all of the finches.
c.	Mate choice likely plays no role in the finches’ evolution.
d.	None of the finch species is reproductively isolated.

Modified True/False (Value 15)
Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true.

36.

Because all members of a population can interbreed, biologists often study their genes as a single group. _________________________

37.

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. _________________________

38.

Most inheritable differences are due to gene shuffling that occurs during the production of gametes. _________________________

39.

Mutations do not always affect an organism’s phenotype—its physical, behavioral, and biochemical characteristics. _________________________

40.

A polygenic trait is controlled by one gene. _________________________

41.

On a graph, the distribution of phenotypes for a single-gene trait tends to form a bell-shaped curve. _________________________

42.

Natural selection on single-gene traits can lead to changes in allele frequencies. _________________________

43.

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. _________________________

44.

In small populations, an allele can become more or less common simply by chance. _________________________

45.

Genetic drift may occur when a small group of individuals colonize a new habitat. _________________________

46.

When mutations introduce new alleles into a population, genetic variation is disrupted. _________________________

47.

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. _________________________

48.

In the type of reproductive isolation called behavioral isolation, two populations are separated by barriers such as rivers or mountains. _________________________

49.

Two populations that have overlapping ranges can remain reproductively isolated through behavioral isolation or temporal isolation from each other. _________________________

50.

The first step of the speciation of the Galápagos finches likely was the arrival of founders from South America. _________________________