Download Mechanisms of Evolution 1. In their first attempts to genetically

Mechanisms of Evolution
1. In their first attempts to genetically engineer a cow that will make and secrete human growth hormones in
milk, scientists found that they could insert the growth hormone gene into an embryonic calf. When the calf
matures, it produces the hormone. However, they discovered that the altered gene gets lost from the genome
during meiosis.
What is the best explanation of what will happen in a population of genetically altered cows?
A.
B.
C.
D.
The cows will not reproduce because only females will reproduce the altered gene.
The cows will reproduce, but neither males nor females will reproduce the altered gene.
The cows will not reproduce because neither males nor females will reproduce the altered gene.
The cows will reproduce, but only males will reproduce the altered gene.
2. Speciation is the process by which new species
A. are discovered.
B. interbreed with another species.
C. are formed.
D. die out.
3. Severe flooding in an area caused a population of minnows to become split into two separate ponds. Prior to
the separation, the male minnows all had a moderate number of spots.
Following the separation, the first pond was filled with larger fish that fed on minnows, so male minnows with
fewer spots were better able to avoid detection by predators. The minnows in the second pond, however, had
very few predators, and female minnows in this pond preferred to mate with males that had the most spots.
After many generations, the two minnow populations evolved into different species and could no longer
interbreed.
Fish Species
Average # of Spots
Original Species
four to six
New Species 1
zero to two
New Species 2
eight to ten
Which of the following best describes why the two minnow populations evolved into separate species?
Different selective pressures were acting upon the two populations, leading to an increase in genetic
A. variation and the formation of two new species.
Natural selection acted upon the traits of the minnows in the first pond only, causing these fish to evolve
B. into a new species with new adaptations.
The same selective pressures were acting upon both populations, leading to a decrease in genetic
C. variation and the formation of two new species.
Natural selection acted upon the traits of the minnows in the second pond only, causing these fish to
D. evolve into a new species with new adaptations.
4.
The figure above shows plates made from a culture growing bacteria during specified generations. The culture
has white and dark bacteria. After generation 1, scientists applied an experimental drug intended to kill the
bacteria and kept the experimental drug in the culture during successive generations.
Which statement best explains the results of the experiment?
The white bacteria showed resistance to the drug.
A.
B.
C.
D.
Both the dark and the white bacteria showed equal resistance to the drug.
The drug had no effect on the population.
The dark bacteria showed resistance to the drug.
5. Evolution is likely to occur because of
I. the potential for a species' population to increase.
II. genetic differences in offspring.
III. a limited supply of necessary resources.
IV. selection of offspring that are best able to survive.
A. I, II, and III only
B. I and IV only
C. II and IV only
D. I, II, III, and IV
6. In order to be classified in the same species, a group of organisms must be able to
A. live in a common area.
B. eat similar foods and possess a similar diet.
C. interbreed and produce fertile offspring.
D. express the exact same genes and phenotypic traits.
7. Peppered moths use the adaptation of camouflage as protection from predators. They may have a variety of
colors or shades, but before the Industrial Revolution, they were typically white with black speckles. The
Industrial Revolution in the 1880s introduced large-scale pollution into the environment. The pollution resulted
in widespread, dark-colored staining of buildings and trees.
Which of the following was the most likely effect of the Industrial Revolution on peppered moths in cities?
A.
B.
C.
D.
The population of light-colored moths decreased and the population of dark-colored moths increased.
The peppered moths adapted an improved sense of sight and smell.
Over time, the white, speckled moths were outnumbered by plain white moths.
The peppered moths developed a tolerance to smog and chemical waste.
8. Some organisms have favorable traits that are well-suited to the environment in which they live. Organisms
with this advantage are more likely to thrive, reproduce, and pass their traits to future generations than
organisms without favorable traits.
This process is known as
A. reproductive isolation.
B. natural selection.
C. mimicry.
D. geographic isolation.
9.
The graph above shows the frequency distribution of a population of fish before and after scientists engaged in
a breeding program over many generations.
Which of the following explanations best describes the program?
The average size of the population decreased because the scientists selected for smaller individuals.
A.
B.
C.
D.
The population spontaneously grew larger.
The average size of the population did not change because no selection occurred.
The average size of the population increased because the scientists selected for larger individuals.
10. Imagine an earthquake creates a chasm that separates a population of squirrels. The two populations of
squirrels evolve into two separate species. What is the name of the process by which isolated populations of
the same species become new species?
A. natural selection
B. speciation
C. reproductive isolation
D. genetic variation
11. A population of lizards lives in a marsh near the ocean. Members of this population have striped tails that
can be yellow, orange, or red. Most members of the population have yellow striped tails.
During a storm, four lizards get swept into the ocean on driftwood and end up on an island several miles away.
All four of the lizards have orange striped tails. These lizards start a new population on the island, and all
members of the new population have orange striped tails.
In the example above, the new lizard population had less genetic variation than the original population because
of _______.
A. gene flow
B. speciation
C. natural selection
D. the founder effect
12. Which of the following is true about natural selection?
Natural selection acts upon asexually reproducing populations that lack genetic variation among
A. individual organisms.
Natural selection causes changes in individual organisms because individuals adapt during their lifetime
B. to better suit their environment.
Natural selection acts upon individual organisms by changing their genetic code through a process
C. known as gene flow.
Natural selection causes changes in populations because of the differential reproductive success of
D. genetically varied individuals.
13. Which of the following is best defined as the transfer of genetic information from one population to another?
A. genetic recombination
B. natural selection
C. genetic drift
D. gene flow
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15. A scientist shines low levels of ultraviolet radiation on a dish containing colonies of ruby-red bacteria. He
then makes several replicate plates from this dish over many generations. He finds that in addition to the rubyred color, there are also pink, orange, and yellow bacteria.
Which of the following is the best explanation for these findings?
A.
B.
C.
Natural selection produced the changes in the bacterial color.
The scientist selected new types of bacteria by making plates of successive generations over time.
One bacterial colony changed its color to better blend in to the media.
Mutations occurred in the gene for color of the bacteria, which were passed on to successive
D. generations.
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18. Genetic drift can best be defined as
A.
B.
C.
D.
the transfer of alleles from one breeding population to another.
the adaptation of a population due to environmental changes.
a change in the allelic frequency within a population due to differential reproductive success.
a change in the allelic frequency within a population due to random chance.
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20. A small population of a specific bird species lives on an island in the Pacific Ocean. All of the birds of this
species have a crest of feathers on their heads. The color of the crest can be orange, yellow, or white. An
individual's crest color does not effect its chance of survival or its reproductive success.
A hurricane hits the island and all of the birds with orange crests are killed, as well as many of the individuals
with yellow and white crests. This causes the gene for orange crests to be lost from the population.
The loss of the gene coding for an orange crest in the bird population described above is an example
of _______.
A. genetic drift
B. natural selection
C. genetic recombination
D. gene flow
21. Allele frequency refers to the fraction of individuals with a particular version of a given gene.
What effect does genetic drift have on the allele frequency of a population?
It greatly reduces the total population, which increases the effects of natural selection on allele
A. frequency.
It causes the allele frequency to resemble that of a small number of individuals that became separated
B. from the rest of the population.
C.
D.
It causes random changes and the allele frequency of certain traits may increase or decrease.
It increases the frequency of alleles that improve a species' survival in a particular environment.
22. A population of deer gets exposed to a pesticide that produces mutations in one of the following types of
cells. In which type of cell will a mutation be most likely to alter the make-up of the population?
A. muscle cell
B. sperm cell
C. brain cell
D. blood cell
23. Several species of finch live on the Galapagos Islands. They are very similar in appearance, but have
adapted beaks of different sizes and shapes based on their major food source. Finches with large beaks eat
mainly large seeds and cacti. Finches with small beaks eat mainly small seeds and insects.
Which of the following best explains the variety of beaks found in finches on the Galapagos Islands?
Biological evolution does not have any effect on the species diversity of an ecosystem.
A.
B.
C.
D.
Evolution through natural selection can increase the species diversity of an ecosystem.
Evolution through natural selection always causes a decrease in the species diversity of an ecosystem.
Biological evolution only affects the species diversity of plants in an ecosystem.
24. An individual hydra is swept by an ocean current to an area of the ocean where no other hydras reside.
The hydra asexually reproduces, as does its offspring, until there is a population of genetically identical hydra.
Is it possible for this population to undergo natural selection?
A. Yes, all populations are capable of undergoing natural selection.
B. Yes, the population will undergo changes in order to become better adapted to the new environment.
C. No, there is no genetic variation upon which natural selection can operate.
D. No, natural selection does not occur in organisms that reproduce asexually.
25. Allele frequency refers to the fraction of individuals with a particular version of a given gene.
What effect does a bottleneck have on the allele frequency of a population?
It causes the allele frequency to resemble that of a small number of individuals that became separated
A. from the rest of the population.
B.
C.
It greatly reduces the total population, which increases the effects of genetic drift on allele frequency.
It increases the frequency of alleles that improve a species' survival in a particular environment.
It causes allele frequency to change randomly and greatly increases the genetic diversity of the
D. population.
26. A mutation exists in a gene that controls hair growth on the middle digit of human fingers. Some people
have mid-digital hair, while others do not. The gene can be passed from one generation to the next.
Which explanation best predicts what should happen to this trait over time?
A.
The incidence of mid-digital hair will decrease in the population because it has a selective disadvantage.
The incidence of mid-digital hair will not change because it offers no selective advantage or
B. disadvantage.
The incidence of mid-digital hair will increase in the human population because it offers a selective
C. advantage.
D.
The incidence of mid-digital hair will increase because it offers no selective advantage.
27. A population of lizards lives on Island A. On nearby Island B, another population of the same species is
present. The lizards on Island A have evolved to have a large frill around their necks. The lizards on Island B,
on the other hand, have evolved to have a much smaller neck frill.
Both islands are colonized by humans and some of the lizards on Island A are transferred to Island B. The
lizards from Island A interbreed with the lizards on Island B. The alleles coding for the large neck frill are
passed onto the offspring resulting from these breedings, introducing new genetic variation into the population.
The transfer of genetic information that occurs between the two lizard populations above is known as
A. natural selection.
B. genetic drift.
C. gene flow.
D. genetic recombination.
28. Speciation occurs during the evolutionary development, or phylogeny, of a species. In which of the
following situations can speciation occur?
A. When two populations are reproductively isolated.
B. When a population becomes extinct.
C. When two populations merge to become one population.
D. When a population becomes interbred.
29. In the living world, there is a great deal of genetic variation. The genetic information of dogs differs from the
genetic information of cats; the genetic information of plants differs from the genetic information of bacteria;
your genetic information differs from your father's genetic information; and so on.
Which of the following is least likely to be a source of genetic variation among living organisms?
A. asexual reproduction
B. mutations
C. sexual reproduction
D. meiosis
30. All species have a certain amount of genetic diversity within their populations. How is genetic diversity
important to the concept of natural selection?
A. Genetic diversity decreases the generation time of species, which contributes to rapid natural selection.
B. Genetic diversity controls the speed at which natural selection is able to occur.
C. Without genetic diversity, natural selection cannot occur.
D. The more genetic diversity a species has, the less likely it is that natural selection will occur.
Answers
1. B
2. C
3. A
4. D
5. D
6. C
7. A
8. B
9. D
10. B
11. D
12. D
13. D
14. -15. D
16. -17. -18. D
19. -20. A
21. C
22. B
23. B
24. C
25. B
26. B
27. C
28. A
29. A
30. C
Explanations
1. The altered gene gets lost during meiosis, which produces the reproductive sex cells: eggs and sperm. The
cows will reproduce normally, but none of the offspring will have the altered gene. So, the presence of the
altered gene will not affect the genetic make-up of the population from one generation to the next.
2. Speciation is the process by which new species are formed.
Speciation can occur when groups of the same species become separated by a natural occurrence, such as
formation of a deep gorge.
During speciation, organisms in the various groups develop sufficient genetic differences they can no longer
interbreed with each other.
3. Different selective pressures were acting upon the two minnow populations, leading to an increase
in genetic variation and the formation of two new species.
Organisms evolve to best fit their environment. When a species is put into new environmental conditions, this
often leads to the formation of a new species. If a population is split, it is possible for two new populations to
form because of different selective pressures acting on the two populations.
4. The frequency of dark bacteria in the population was low. The presence of the drug reduced the frequency
of the white bacteria and increased the frequency of the dark bacteria. It can be concluded that the dark
bacteria were resistant to the drug and were able to reproduce successfully over time.
5. Species evolve over time as a result of




the potential for a species' population to increase.
genetic differences in offspring due to mutation and the recombination of genes.
a limited supply of necessary resources.
selection by the environment of offspring that are best able to survive and reproduce.
6. Species are reproductively distinct groups of organisms. That is, in order to be classified in the same
species, a group of organisms must be able to interbreed and produce fertile offspring.
7. After the Industrial Revolution began, the pollution began staining buildings and trees in a dark, blackish
color. While on these dark-colored surfaces, the light-colored peppered moths were much more visible to
predators than before. On the other hand, the rare, dark-colored peppered moths had a new advantage: they
camouflaged well with the dark surfaces, and thus were less visible to predators.
So, the most likely effect of the Industrial Revolution on peppered moths in cities was that population of lightcolored moths decreased and the population of dark-colored moths increased.
8. Favorable traits are traits that promote an organism's success in a particular environment. Organisms with
favorable traits are more likely to thrive, survive, and reproduce than organisms without favorable traits. In this
way, nature "selects" which traits (or even which types of organisms) will continue to exist in a population.
9. The graph shows that the average size of the population increased. You can conclude from the breeding
program that the scientists selected for larger individuals. This is artificial selection, but demonstrates
directional selection.
10. The accumulation of differences between groups is called divergence. Divergence leads to the formation of
new species through the process of speciation.
11. The founder effect is an extreme form of genetic drift that occurs when a few members of a larger
population establish a new, isolated population.
The genetic variation of the new population will be drastically reduced from that of the original population since
only the alleles carried by the founding members will be present in the new population. Specific genetic traits
from the original population can be lost or over-represented by the new population, depending on the alleles
present in the founding members.
12. Natural selection is a process by which organisms with traits well suited to an environment survive and
reproduce at a greater rate than organisms less suited to that environment. Natural selection causes
changes in populations of organisms, as opposed to individual organisms, because it requires the
differential reproductive success of genetically varied individuals.
13. Gene flow is the transfer of genetic information from one population to another. Gene flow can be caused
by many different events, such as pollen being spread to a new area by the wind or humans transferring
animals from one location to another.
Gene flow can be an important source of genetic variation when unique genetic information from one
population is introduced into a different population.
14. -15. Evolution needs both variations and natural selection to evolve a species. Mutations are important in how
populations change over time because they result in genetic changes to the gene pool.
In this experiment, ultraviolet radiation induced mutations in the gene for color, which is why new colors of
bacteria appeared. However, since neither nature nor the scientist applied any selection, the variations in
colors remained.
16. -17. -18. Genetic drift is a change in the allelic frequency within a population due to random chance. It is
especially apparent within small breeding populations.
For example, genetic drift can result in an allele being completely lost from a population by random chance,
regardless of whether the allele has any effect on an individual's chance of survival or its reproductive success.
19. -20. Genetic drift is a change in the allelic frequency within a population due to random chance. It is especially
apparent within small breeding populations.
For example, genetic drift can result in an allele being completely lost from a population by random chance,
regardless of whether the allele has any effect on an individual's chance of survival or its reproductive success.
21. Genetic drift causes random changes in allele frequency, which means that the allele frequency of
certain traits may increase or decrease. It is more pronounced in smaller populations.
22. Natural selection acts upon the mutations that are inherited from one generation to the next. Of the cell
types listed, only the genes in the sperm cell will get passed on to future generations and will have the
potential to alter the make-up of the population.
23. The diversity of species is the result of speciation, or the splitting and divergence of former species into
new species. Speciation occurs as organisms evolve to better fit their environment. For example, the finches
on the Galapagos Islands evolved different sized and shaped beaks based on the food sources that were
easily accessible to them.
Evolution through natural selection can increase the species diversity of an ecosystem.
24. Natural selection could not occur if there was no genetic diversity amongst species. In this case, the only
way natural selection could occur is if one of the offspring experiences a genetic mutation, which would
introduce genetic diversity into the population.
25. Genetic drift causes random changes in allele frequency. It is more pronounced in smaller populations.
Drastic changes in the environment, like a food shortage or an outbreak of disease, can cause a bottleneck in
which the total population shrinks quickly and dramatically. When this happens, it increases the effects of
genetic drift on allele frequency.
26. Whether you have mid-digital hair or not gives you no special advantage or disadvantage for survival. So,
natural selection does not change the frequency of this gene in the population. Therefore, the incidence of middigital hair should not change in the human population.
27. Gene flow is the transfer of genetic information from one population to another. Gene flow can be caused
by many different events, such as pollen being spread to a new area by the wind or humans transferring
animals from one location to another.
Gene flow can be an important source of genetic variation when unique genetic information from one
population is introduced into a different population.
28. The environment differs from place to place. Therefore, populations of the same species living in different
places tend to evolve in different directions. When two populations that are evolving in different directions
become isolated from one another and cannot reproduce with each other, speciation may occur.
29. There are many sources of genetic variation among living organisms.
Mutations, or changes to an organism's genetic material, are a significant source of genetic variation.
Sexual reproduction results in an offspring that has a combination of genetic material from its parents, which
contributes to genetic variation.
Meiosis is the process by which sexually-reproducing organisms produce unique gametes, or sex cells. The
unique gamete of one parent can fuse with the unique gamete of another parent to produce a unique offspring,
resulting in increased genetic variation.
Asexual reproduction requires only one parent and produces offspring that are genetically-identical to the
parent. Therefore, asexual reproduction is least likely to be a source of genetic variation.
30. Natural selection could not occur if there was no genetic diversity amongst species. Furthermore, the
process of natural selection, which leads to speciation, can enhance the genetic diversity of species.