Mastering Biology Exam 2

Question 1

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele?

Answer 1

.09

Question 2

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.2. What is the frequency of individuals that are heterozygous for this allele?

Answer 2

.32

Question 3

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population?

Answer 3

.8

Question 4

Evolution

Answer 4

can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met.

Question 5

If the original finches that had been blown over to the Galápagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galápagos, this would have been an example of

Answer 5

both the first and third of these. (genetic drift & founder effect)

Question 6

Which type of selection tends to increase genetic variation?

Answer 6

Disruptive selection

Question 7

In a bell-shaped curve, the x-axis (horizontal direction) of the graph represents which of the following?

Answer 7

The value of a particular characteristic; characteristics of an organism can include such traits as size and color

Question 8

True or false? Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population.

Answer 8

False

Question 9

Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in “neck wrestling” contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today?

Answer 9

Directional selection

Question 10

Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies?

Answer 10

Stabilizing selection

Question 11

Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers?

Answer 11

Disruptive selection

Question 12

Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards?

Answer 12

Stabilizing selection

Question 13

In evolutionary terms, an organism’s fitness is measured by its _____.

Answer 13

contribution to the gene pool of the next generation

Question 14

Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____.

Answer 14

directional selection

Question 15

What is the only evolutionary mechanism that consistently leads to adaptive evolution?

Answer 15

natural selection

Question 16

Sexual dimorphism is most often a result of

Answer 16

intersexual selection.

Question 17

What is genetic drift?

Answer 17

A change in allele frequencies caused by random events

Question 18

Why are the large finches now living on the Galápagos Islands different from the original source population from a nearby island?

Answer 18

All three answers are correct.

Question 19

True or false? The last ice age produced many different species mainly because populations dispersed and colonized new habitats.

Answer 19

False

Question 20

Which of the following statements about reinforcement is true?

Answer 20

Reinforcement is a type of natural selection.

Question 21

A subset of a population of birds leaves its habitat on the mainland and colonizes a nearby island. The birds, after a period of time, become reproductively isolated. The island sinks and the population of birds that lived on the island returns to its original habitat. Which of the following statements about these bird populations is true?

Answer 21

The populations will not be able to interbreed because they are different species.

Question 22

A population of birds colonizes an area in which the insects upon which they feed live inside trees. Which of the following events accounts for an observed increase in average beak size in the bird population over time?

Answer 22

Increased fitness of large-beaked birds, leading to natural selection

Question 23

True or false? A flood that separates a population of frogs onto opposite sides of a lake is an example of a vicariance event that may result in allopatric speciation.

Answer 23

True

Question 24

Which of these is an example of temporal isolation?

Answer 24

One species is nocturnal, and the other species is not.

Question 25

Which of the following is the first step in allopatric speciation?

Answer 25

geographic isolation

Question 26

Sympatric speciation is _____.

Answer 26

the appearance of a new species in the same area as the parent population

Question 27

The origin of a new plant species by hybridization, coupled with accidents during cell division, is an example of

Answer 27

sympatric speciation.

Question 28

The phenomenon of fusion is likely to occur when, after a period of geographic isolation, two populations meet again and

Answer 28

an increasing number of viable, fertile hybrids is produced over the course of generations.

Question 29

Feathers either play a role, or may have played a role, in _____.

Answer 29

gliding
extended hops
flight
courtship

Question 30

_____ is rapid speciation under conditions in which there is little competition.

Answer 30

Adaptive radiation

Question 31

Mass extinctions create conditions that promote _____.

Answer 31

adaptive radiation

Question 32

The appearance of an evolutionary novelty promotes _____.

Answer 32

adaptive radiation

Question 33

The different finch species found on the Galápagos Islands probably arose as a result of _____.

Answer 33

adaptive radiation

Question 34

What is the most important factor that holds a gene pool of a species together and prevents speciation?

Answer 34

gene flow

Question 35

Two animals are considered members of different species if they _____.

Answer 35

cannot mate and produce viable, fertile offspring

Question 36

What is true of macroevolution?

Answer 36

It is evolution above the species level.

Question 37

What is true of the flightless cormorants of the Galápagos Islands?

Answer 37

Flightless cormorants on one island have restricted gene flow with those on other islands, which could someday lead to a macroevolutionary event.

Question 38

Which of the following statements about species, as defined by the biological species concept, is (are) correct?

Answer 38

I. Biological species are defined by reproductive isolation.

III. The biological species is the largest unit of population in which successful interbreeding is possible.

Question 39

Dog breeders maintain the purity of breeds by keeping dogs of different breeds apart when they are fertile. This kind of isolation is most similar to which of the following reproductive isolating mechanisms?

Answer 39

habitat isolation

Question 40

Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. If pollen grains (which contain sperm cells) from one species are unable to germinate and make pollen tubes on female ovules (which contain egg cells) of the other species, then which of these terms is applicable?

Answer 40

mechanical isolation

Question 41

What does the biological species concept use as the primary criterion for determining species boundaries?

Answer 41

gene flow

Question 42

In a hypothetical situation, a certain species of flea feeds only on pronghorn antelopes. In rangelands of the western United States, pronghorns and cattle often associate with one another. If some of these fleas develop a strong preference for cattle blood and mate only with other fleas that prefer cattle blood, then over time which of these should occur, if the host mammal can be considered as the fleas’ habitat?

Answer 42

1. reproductive isolation
2. sympatric speciation
3. habitat isolation
4. prezygotic barriers

Question 43

Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. If pollen grains (which contain sperm cells) from one species are unable to germinate and make pollen tubes on female ovules (which contain egg cells) of the other species, then which of these terms are applicable?

Answer 43

1. sympatric species

2. prezygotic isolation