Download 17.1 Genes and Variation Name: Biology Date: Period: Genetics

17.1 Genes and Variation
Name:
Biology
Date:
Period:
Genetics Joins Evolutionary Theory
Complete each statement by writing the correct word or words.
1. Natural selection works on an organism’s
2. A(n)
rather than its
.
consists of all the genes, including the alleles for each gene, that are
present in a population.
3. A gene pool typically contains different
for each heritable trait.
4. The number of times that an allele occurs in a gene pool compared with the number of times other alleles for
the same gene occur is called the
of the population.
Use the circle graph of a sample mouse population to answer the following questions.
5. In the diagram below, use circles to represent the alleles within each segment of the population. Draw the B
alleles as solid circles and the b alleles as outline circles.
a. The total number of individuals in this population is
; the total number of alleles is
.
b. How many alleles for black fur are in the sample population and what percentage of allele frequency
does that represent?
c. How many alleles for brown fur are in the sample population and what percentage of allele frequency
does that represent?
d. Describe how a geneticist might be able to tell that this population is evolving.
6. Can you determine whether an allele is dominant or recessive on the basis of the ratio of phenotypes in the
population? Explain your answer.
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Sources of Genetic Variation
7. What are mutations? When do they affect evolution?
8. How does sexual reproduction affect a population’s genetic variation?
9. Identify two ways in which genes can be recombined during meiosis.
10. Why is genetic variation important to the process of evolution?
Single Gene and Polygenic Traits
11. Label the two graphs to show which represents a single-gene trait and which represents a polygenic trait.
Write True if the statement is true. If the statement is false, change the underlined word or words to make the
statement true.
12.
The number of phenotypes produced for a given trait depends on how many genes
control the trait.
13.
Height in humans is an example of a single-gene trait.
14.
Each gene of a polygenic trait often has two or more phenotypes.
15.
A single polygenic trait often has many possible genotypes.
16.
A symmetrical bell-shaped graph is typical of polygenic traits.
2
Use the Venn diagram to compare and contrast single-gene traits and polygenic traits.
Single-Gene Traits
Both
Polygenic Traits
Concept Map A concept map helps you see how the topics you read about are related to one another. Use the
words and phrases below to fill in the empty spaces in the concept map.
Genetic recombination
Chromosomes
Genes
Crossing-over
Sources of
Genetic Variation
include
Lateral gene
transfer
Mutations
involve changes in
happens during
Meiosis
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Single-Gene and Polygenic Traits
Polygenic Traits Some traits are controlled by only one gene. They are called single-gene traits. Other traits are
controlled by two or more genes. They are called polygenic traits. Human height is an example of a polygenic
trait.
Height in
cm
155–159
160–164
165–169
170–174
175–179
180–184
185-189
190–194
Number of
Students
1
2
6
10
10
6
2
1
1. Draw a curve connecting
the data points.
2.
What shape is the curve you drew?
a. bell curve
b. one-sided curve
3. What is the average height for this population?
a. 155–164 cm
b. 165–174 cm
c. irregular curve
c. 170–179 cm
d. 185–194 cm
17.2 Evolution as Genetic Change in Populations
Term
Definition
A change in an allele’s frequency following a dramatic reduction
in population size
Form of natural selection in polygenic traits in which the entire
curve shifts because some individuals are more successful at
surviving
Form of natural selection in polygenic traits in which the curve
splits in two because individuals at the two ends are more
successful at surviving than those in the center
A change in an allele’s frequency that occurs as a result of a
migration of a small part of the population
A random change in an allele’s frequency
When all of the alleles in a population remain the same
The process of selecting a mate based on traits like strength or
color
Form of natural selection in polygenic traits in which the center of
the curve stays in the same position because the individuals in the
center are more successful at surviving
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How Natural Selection Works
1. If a trait made an organism less likely to survive and reproduce, what would happen to the allele for that
trait?
2. If a trait had no effect on an organism’s fitness, what would likely happen to the allele for that trait?
Use the table showing the evolution of a population of mice to answer the following questions.
Initial Population Generation 10
Generation 20
Generation 30
90%
80%
70%
40%
10%
20%
30%
60%
3. Is the trait for fur color a single-gene trait or a polygenic trait? Explain your answer.
4. Describe how the relative frequency of fur color alleles is changing in this population and propose one
explanation for this change.
5. Suppose a mutation causes a white fur phenotype to emerge in the population. What might happen to the
mouse population after 40 generations?
6. What effect does stabilizing selection have on variation in a population?
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original
population
original
population
Number of Birds in
Population
Percentage of
Human Population
Natural Selection on Polygenic Traits In most populations, a trait that has higher fitness leads to greater
numbers of organisms with that trait. The solid lines show the population after selection has taken place. Label
the graphs as disruptive selection or stabilizing selection.
Birth Weight
__________________________
Beak Size
__________________________
7. With which type of selection do organisms in the middle of the curve have the highest fitness?
8. In disruptive selection, organisms on which part of the curve have the lowest fitness?
9. How does the curve change in stabilizing selection? The curve
a. becomes shorter and wider.
c. moves to the right.
b. becomes taller and narrower.
10. The plants in an area have either very small or very large seeds. Birds with small beaks can eat small seeds,
and birds with large beaks can eat large seeds. Birds with smaller beaks and birds with larger beaks become
more common than birds with medium beaks. What type of selection is this?
a. stabilizing selection
b. disruptive selection
c. directional selection
Genetic Drift – Use what you know about the Hardy-Weinberg principle to identify what is happening.
11. Genetic drift strongly affects the population.
a. small population
b. random mating
c. no movement into or out of the population
d. no natural selection
12. Lions with a darker fur color have the same chance to reproduce as lions with a lighter fur color.
a. large population
c. no mutations
b. random mating
d. no natural selection
13. Fitness is basically the same among individuals in the population.
a. large population
c. no mutations
b. random mating
d. no natural selection
14. In small populations, random changes in
is called genetic drift.
15. A situation in which allele frequencies change as a result of the migration of a small subgroup of a
population is known as the
16. The
.
is a change in allele frequency following a dramatic reduction in
the size of a population.
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Complete the concept map.
Genetic Drift
can result from
Bottleneck Effect
caused by
caused by
Evolution Versus Genetic Equilibrium
17. What does the Hardy-Weinberg principle state?
18. What is genetic equilibrium?
19. Use phrases in the word box to identify each condition that leads to genetic equilibrium.
large population
random mating
no natural selection
no mutations
no movement
The Hardy-Weinberg Principle
The more individuals in the population, the smaller the
effect of genetic drift.
No changes to genes means new alleles are not introduced
into the population’s gene pool.
Each individual in a population has the same chance of
passing on its alleles.
No new alleles are introduced into the population’s gene
pool by new individuals.
No phenotype can have a selective advantage over another—
all individuals have equal fitness.
20. Explain how sexual selection results in non-random mating.
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21. Suppose a population of insects live in a sandy habitat. Some of the insects have tan bodies and some have
green bodies. Over time, the habitat changes to a grass-filled meadow. Use the ideas of natural selection to
explain how and why the insect population might change.
17.3 The Process of Speciation
Isolating Mechanisms
1. What is speciation?
2. What does it mean for two species to be reproductively isolated from each other?
3. What must happen in order for a new species to evolve?
4. Many finch characteristics appear in bell-shaped distributions typical of
traits.
5. The ancestors of the Galápagos Island finches originally came from the continent of
.
6. The populations of finches on separate islands are
isolated from one another by
large stretches of open water.
Populations Become Isolated - Read the chart below. Then, use phrases in the word box to identify each
process that leads to speciation.
changes in the gene pool
geographic isolation
founders arrive
competition
behavioral isolation
Process
How It Leads to Speciation
A population arrives in a new place.
Populations are separated by a geographic barrier and do not
share a gene pool.
Populations evolve new traits in response to natural selection
in their environments.
Species evolve in a way that reduces competition between
them.
Groups within a population are separated by different
courtship rituals.
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Speciation in Darwin’s Finches - Charles Darwin proposed that the different species of finches on the
Galapagos Islands once had a common ancestor. Over time, he said, natural selection led to each species of
finch. A current hypothesis says that speciation in the Galapagos finches occurred through the founding of a
new population, geographic isolation, changes in the new population’s gene pool, behavioral isolation, and
ecological competition. Use the phrases in the box to complete the chart.
insects that live inside dead wood
fruits
large, thick-shelled seeds
small seeds
Galápagos Islands Finches
Shape of
head and
beak
Main food
Feeding
adaptation
Habitat
Parrot-like beak
uses cactus spines
pointed crushing
beak
large crushing beak
trees
trees
ground
ground
7. How does the large crushing beak help the fourth finch survive?
8. Circle the finch that would be least likely to survive if the insect population decreased.
9. Both the first and second finch live in trees. Suppose one season there is less fruit in the trees. Which finch
is more likely to survive and reproduce?
Populations Become Isolated
Speciation occurs when a new species evolves. Many things contribute to speciation. Read the chart below and
use phrases in the word box to identify each process that leads to speciation.
changes in the gene pool
geographic isolation
founders arrive
competition
behavioral isolation
Process
How It Leads to Speciation
A population arrives in a new place.
Populations are separated by a geographic barrier and do not share a gene
pool.
Populations evolve new traits in response to natural selection in their
environments.
Species evolve in a way that reduces competition between them.
Groups within a population are separated by different courtship rituals.
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10. Finches prefer to find mates with the same size beaks. Finches in Group A have larger beaks than those in
Group B, so finches from the two groups will not mate. What is this an example of?
11. Do populations that are geographically isolated from one another share a gene pool? Why or why not?
12. Complete the table with the correct terms.
Term
Definition
The number of times an allele appears in a gene pool, compared to
the total number of alleles in that pool for the same gene.
A common group of genes, and all their alleles, shared by a
population
A trait controlled by two or more genes
A trait controlled by only one gene
A change in an allele’s frequency following a dramatic reduction in
population size
Form of natural selection in polygenic traits in which the entire curve
shifts because some individuals are more successful at surviving
Form of natural selection in polygenic traits in which the curve splits
in two because individuals at the two ends are more successful at
surviving than those in the center
A change in an allele’s frequency that occurs as a result of a
migration of a small part of the population
A random change in an allele’s frequency
When all of the alleles in a population remain the same
The process of selecting a mate based on traits like strength or color
Form of natural selection in polygenic traits in which the center of
the curve stays in the same position because the individuals in the
center are more successful at surviving
When two populations have different behaviors that keep them from
reproducing
When two populations are separated by geographic features, such as
rivers or mountains, that keep them from reproducing
Separation of populations so that they cannot reproduce
A population or group of populations whose members can interbreed
and produce fertile offspring
The forming of a new species
When two populations reproduce at different times, so that they
cannot reproduce together
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Types of Natural Selection
A group of snakes were all placed into environments that had differing selective pressures. Read the data tables
below and graph each snake in its environment. From the graph, determine what type of selection is being
portrayed: directional, stabilizing or disruptive.
1. Snakes were placed on an island where there are two predators that eat snakes.
Year
2000
2004
2008
Number of Snakes at Each Length
2 cm
4cm
6 cm
8 cm
2
14
18
12
4
12
8
9
10
6
3
6
10 cm
4
8
14
Type of Selection:
Summarize what happened
to the snakes.
2. Snakes were placed on an island where there is only one size of burrow available to the snakes to live in.
Year
2000
2004
2008
Number of Snakes at Each Length
2 cm
4cm
6 cm
8 cm
4
12
16
10
3
10
18
9
1
6
24
2
10 cm
3
3
1
Graph is on the next page.
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Type of Selection:
Summarize what happened
to the snakes.
3. Snakes placed on an island where there is only one predator, a snake eating toad. This
toad can only eat snakes under 6 cm long.
Year
1980
1984
1988
Number of Snakes at Each Length
2 cm
4cm
6 cm
4
12
14
2
6
9
1
2
2
8 cm
8
12
15
10 cm
12
14
18
Type of Selection:
Summarize what happened
to the snakes.
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Types of Natural Selection
1. Limpets are marine organisms that have shells that vary in color from white to dark brown. Limpets live
their adult life attached to rocks. On light colored rock, white shelled limpets are at an advantage because
the birds that prey upon them have a difficult time locating them. On dark-colored rock, dark-shelled
limpets are well camouflaged. On the other hand, tan-colored limpets are easily spotted on either light or
dark rocks.
Name the type of selection: _____________________________________________
Explain why this type of selection occurred:
__________________________________________________________________________________________
__________________________________________________________________________________________
2. In spiders, the average size is at an advantage in terms of survival and reproduction. Large spiders are
easily seen and captured by their predators. Smaller than average spiders cannot catch enough prey to
survive.
Name the type of selection: ______________________________________________
Explain why this type of selection occurred:
__________________________________________________________________________________________
__________________________________________________________________________________________
3. Woodpeckers feed by pecking holes in trees in order to get at the insects living under the bark. One year,
the trees are invaded by insects that live deep within the trees. Woodpeckers with short beaks can’t reach
insects and starve. Only the woodpeckers with long beaks can eat and survive.
Name the type of selection: ______________________________________________
Explain why this type of selection occurred:
__________________________________________________________________________________________
__________________________________________________________________________________________
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4. In crossbills, a finch-like bird that lives in mountain forests, bill size is directly related to the size of seeds
that are eaten. Small seeds are eaten by birds with small bills while large seeds are eaten by birds with large
bills. Birds with a bill of intermediate size feed on seeds
of intermediate size.
A specific population of crossbills has a distribution
similar to the one at the right. Questions # a-d present
four types of environmental change that might impact
this population. For each potential change, choose the
distribution below that best suggests how this population
of crossbills would adjust. Compare each question
separately to the original starting population at the right. Any of the distributions (A-E) may be used once,
more than once, or not at all.
_____ a.
Over a 10-year period, various species of seed-eating ants invade the area and disproportionately
consume a much greater number of intermediate-sized seeds.
_____ b.
For 15 growing seasons colder than normal temperatures gradually favor the production of larger
seeds while plants producing smaller seeds do not survive and reproduce as well.
_____ c.
A new species of finch, with a bill-size distribution similar to that of the crossbills, moves in to
the area. If combined onto one graph, which would be the most likely graph?
_____ d.
Unidentified environmental factors, acting through natural selection, decrease the amount of
variation in bill size among the crossbills.
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Population Genetics and Hardy-Weinberg Genetic Equilibrium
Name:
Evolution
Date:
Period:
The Hardy-Weinberg formulas allow scientists to determine whether evolution has occurred. Any changes in
the gene frequencies in the population over time can be detected. The principle states that if no evolution is
occurring, then equilibrium of allele frequencies will remain in effect in each succeeding generation of sexually
reproducing individuals. In order for equilibrium to remain in effect (i.e.no evolution is occurring) then the
following five conditions must be met:
1.
2.
3.
4.
No mutations must occur so that new alleles do not enter the population.
No gene flow can occur (i.e. no migration of individuals into, or out of, the population).
Random mating must occur (i.e. individuals must pair by chance).
The population must be large so that no genetic drift (random chance) can cause the allele frequencies to
change.
5. No selection can occur so that certain alleles are not selected for, or against.
Obviously, the Hardy-Weinberg equilibrium cannot exist in real life. Some or all of these types of forces all act
on living populations at various times and evolution at some level occurs in all living organisms. The HardyWeinberg formulas allow us to detect some allele frequencies that change from generation to generation, thus
allowing a simplified method of determining that evolution is occurring. There are two formulas that must be
memorized:
p2 + 2pq + q2 = 1 and p + q = 1
(frequency of AA) + (frequency of Aa) + (frequency of aa) = 100%
p = frequency of the dominant allele in the population
q = frequency of the recessive allele in the population
p2 = percentage of homozygous dominant individuals
q2 = percentage of homozygous recessive individuals
2pq = percentage of heterozygous individuals
Example for Hardy Weinberg Equation
Albinism is a rare genetically inherited trait that is only expressed in the phenotype of
homozygous recessive individuals (aa). The most characteristic symptom is a marked deficiency in the skin and
hair pigment melanin. This condition can occur among any human group as well as among other animal
species. The average human frequency of albinism in North America is only about 1 in 20,000.
Referring back to the Hardy-Weinberg equation (p² + 2pq + q² = 1), the frequency of homozygous recessive
individuals (aa) in a population is q². Therefore, in North America the following must be true for albinism:
By taking the square root of both sides of this equation, we get:
In other words, the frequency of the recessive albinism allele (a) is .00707 or about 1 in 140. Knowing one of
the two variables (q) in the Hardy-Weinberg equation, it is easy to solve for the other (p).
The frequency of the dominant, normal allele (A) is, therefore, ________________ or about 99 in 100.
The next step is to plug the frequencies of p and q into the Hardy-Weinberg equation:
15
This gives us the frequencies for each of the three genotypes for this trait in the population:
p² = predicted frequency of homozygous
dominant individuals
2pq = predicted frequency of heterozygous
individuals
q² = predicted frequency of homozygous
recessive individuals (albinos)
With a frequency of ____________ (about 1 in 20,000), albinos are extremely rare. However, heterozygous
carriers for this trait, with a predicted frequency of ____________ (about 1 in 72), are far more common than
most people imagine. There are roughly 278 times more carriers than albinos. Clearly, though, the vast
majority of humans ____________ probably are homozygous dominant and do not have the albinism allele.
PROBLEM #1 - View the Dragons on the right. The winged
trait is dominant.
Frequency
q2 (aa) =
q (a) =
p (A) =
p2 (AA) =
2pq (Aa) =
What is the frequency (%) of the heterozygote dragons in the
population.
PROBLEM #2
You have sampled a population in which you know that the percentage of the homozygous recessive genotype
(aa) is 36%. Using that 36%, calculate the following:
A) The frequency of the "aa" genotype.
B) The frequency of the "a" allele.
C) The frequency of the "A" allele.
D) The frequencies of the genotypes "AA" and "Aa."
E) The frequencies of the two possible phenotypes if "A" is completely dominant over "a."
PROBLEM #3
Within a population of butterflies, the color brown (B) is dominant over the color white (b). And, 40% of all
butterflies are white. Given this simple information, calculate the following:
A) The percentage of butterflies in the population that is heterozygous.
B) The frequency of homozygous dominant individuals.
PROBLEM #4
The ability to taste PTC is due to a single dominate allele "T". You sampled 215 individuals in biology, and
determined that 150 could detect the bitter taste of PTC and 65 could not. Calculate all of the potential
frequencies.
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Biology Keystone Exam Preparation
Natural Selection and Evolution
Keystone Eligible Content:
 Explain how natural selection can impact allele frequency of a population
 Describe the factors that can contribute to the development of new species (e.g. isolating mechanisms,
genetic drift, founder effect, migration)
 Explain how genetic mutations may result in genotypic and phenotypic variations within a population
 Distinguish between stabilizing, disruptive and direction selection.
 Interpret evidence supporting the theory of evolution (i.e. fossil, anatomical, physiological, embryological,
biochemical, and universal genetic code)
 Distinguish between the scientific terms: hypothesis, inference, law, theory, principle, fact, observation
A
B
C
1. Identify the type of selection in graph A _______________________________
2. Identify the type of selection in graph B _______________________________
3. Identify the type of selection in graph C _______________________________
4. In a species of snail, dark individuals are better hidden (from bird predators) in the shady forest, while
lighter individuals are better hidden in well lit brushy edge areas. There are no areas of intermediate
brightness; therefore, ___________ acts on shell color in these snails.
A. directional selection
B. disruptive selection
C. stabilizing selection
5. Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed
upon by owls. This situation results in ________ on adult body size.
A. directional selection
B. disruptive selection
C. stabilizing selection
6. 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, __________ appears to have made giraffes the long-necked
creatures they are today.
A. directional selection
B. disruptive selection
C. stabilizing selection
7. Populations of the same species of seal live on islands too far apart to swim between them for mating.
A. behavioral isolation
B. temporal isolation
C. geographic isolation
8. Species of birds have elaborate courtship dances, and females select the best dancers as mates.
A. behavioral isolation
B. temporal isolation
C. geographic isolation
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9. Varieties of oak tree produce pollen during different seasons, so they can’t pollinate one another.
A. behavioral isolation
B. temporal isolation
C. geographic isolation
10. Herds of caribou misinterpret each other’s mating behavior, so they fight instead of mating.
A. behavioral isolation
B. temporal isolation
C. geographic isolation
11. The frequency of an allele in a fly population changes from 89% to 20% after three generations. Which
other events most likely occurred during the same time period?
A. An environmental change and a fly population increase.
B. An environmental change and a fly population decrease.
C. Interbreeding of flies with an invasive species and fly population speciation.
D. Interbreeding of flies with an established local species and fly population speciation.
Use the graph below to answer question 12.
12. Tail length in mice varies within a population. Scientists observed change in the distribution of tail lengths
in a mouse population over time. At the genetic level, what has most likely happened to the allele for the
shortest tail lengths?
A. The allele changed from being dominant to being recessive.
B. The allele changed from being autosomal to being sex-linked.
C. The allele became less frequent than the alleles for longer tail lengths.
D. The allele began to code for long tail lengths instead of the shortest ones.
Use the circle graphs below to answer question 13.
13. The graphs illustrate change in a lizard population over time. Which process most likely led to the change
in the lizard population?
A. natural selection acting on a harmful trait
B. natural selection acting on a beneficial trait
C. natural selection acting on a dominant trait
D. natural selection acting on a recessive trait
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14. In North America, the eastern spotted skunk mates in late winter, and the western spotted skunk mates in
late summer. Even though their geographic ranges overlap, the species do not mate with each other. What
most likely prevents these two species from interbreeding?
A. habitat isolation
C. geographic isolation
B. gametic isolation
D. reproductive isolation
15. A mutation occurs in the genes that code for coat color in deer. Which change will most likely result from
this mutation?
A. A change in the selection pressures acting on coat color.
B. A change in the coat-color genes of deer predator species.
C. An increase in coat-color diversity in the population.
D. An increase in the number of genes for coat color in the population.
Use the illustrations below to answer the next question.
16. The skeletons of mammalian forelimbs represent variations of a structure that was present in their common
ancestor. What has most likely caused the variation in forelimbs?
A. changes in muscle structure
C. trait formation due to behaviors
B. changes in the genetic codes
D. development of vestigial structures
17. A population of animals is permanently split by a natural barrier into two separate populations in different
environments. What will likely result after a long period of time?
A. The evolution of the two populations will be identical.
B. The production of variations will stop in the two populations.
C. The two populations will evolve into separate species.
D. Autotrophic nutrition will replace heterotrophic nutrition in the two populations.
18. When changes occur in the genes of sex cells, these changes
A. lead to mutations in the parent organism.
B. are always harmful to the offspring.
C. can be the basis for evolutionary change.
D. only affect sexually reproducing organisms.
19. When a species includes organisms with a wide variety of traits, it is most likely that this species will have
A. a high proportion of individuals immune to genetic diseases.
B. a greater chance to survive if environmental conditions suddenly change.
C. less success competing for resources.
D. limitless supplies of important resources, such as food and water.
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20. The sorting and recombination of genes during reproduction is important to evolution because these
processes
A. decrease variation and help maintain a stable population.
B. increase variation that enables species to adapt to change.
C. decrease the chances of producing offspring that are adapted to the environment.
D. increase the ability of all the offspring to adapt to the environment.
21. In the early stages of development, the embryos of dogs, pigs, and humans resemble one another. This
observation suggests that these animals may have
A. a similar number of chromosomes.
C. the same blood components.
B. similar habitat requirements.
D. a common ancestry.
22. The idea that evolution takes place at a continuous but very slow rate is known as
A. succession.
C. punctuated equilibrium.
B. artificial selection.
D. gradualism.
23. Which statement is best supported by the theory of evolution?
A. Genetic alterations occur every time cell reproduction occurs.
B. The fossil record provides samples of every organism that ever lived.
C. Populations that have advantageous characteristics will increase in number.
D. Few organisms survive when the environment remains the same.
24. Differences between the members of a population will most likely be passed to future generations if they are
A. due to genetic changes and result in unfavorable variations.
B. due to genetic changes and result in favorable variations.
C. not due to genetic changes and result in unfavorable variations.
D. not due to genetic changes and result in favorable variations.
25. A gene pool consists of
A. all the genes that mutate in a single generation.
B. all the heritable genes for traits in a population.
C. all the gametes produced by a population.
D. the mutated alleles for a particular trait.
26. A characteristic that an organism exhibits during its lifetime will only affect the evolution of its species if
the characteristic
A. results from isolation of the organism from the rest of the population.
B. is due to a genetic code that is present in the gametes of the organism.
C. decreases the number of genes in the body cells of the organism.
D. causes a change in the environment surrounding the organism.
27. A researcher recently discovered a new species of bacteria in the body of a tubeworm living near a
hydrothermal vent. He compared the DNA of this new bacterial species to the DNA of four other species of
bacteria. The DNA sequences came from the same part of the bacterial chromosome of all four species.
According to these data, the unknown bacterial species is most closely related to
A. species I
B. species II
C. species III
D. species IV
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28. Which species in the chart below is most likely to have the fastest rate of evolution?
29. The gene COII is in the genome of many organisms. A comparison of the number of base differences
between the COII gene in a rat and that of two other animals is shown.
A. Based on the data, describe a possible evolutionary relationship between rats, mice, and cows.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
B. Describe how different organisms having a common gene such as COII supports the theory of evolution.
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
C. The COII gene of a monkey has 203 base differences from the same gene in a rat and 201 base differences
from the same gene in a mouse. Compare the evolutionary relationships between the monkey, the rat, and
the mouse.
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