PCB 3044 Exam 2 Review (Cook) - Questions with
Correct Answers (Verified Update)
107 questions with answers
Topic: PCB 3044 Exam 2 Review (Cook)
1. How does hunting affect natural populations? What is trophy -Trophy hunting, and
how does this change the genetic makeup of the population offspring? What affect
has this had on the ram? What has happened to maturation time in cod? Why?
Answer: -One way hunting attects natural populations is by causing evolutionary change.
hunting is hunting for sport and displaying parts of an animal as trophies. Trophy hunting
causes the genetic characteristics of a population to change, or evolve. -This means rams
with small horns are able to reproduce more frequently than rams with bighorns, resulting in
more small horn rams. -In cod fishery, harvesting practices have selected individuals that
mature at a younger age and a smaller size for production purposes.
2. Define evolution. Explain using gene frequency. What is required of a trait for
natural selection to act upon it?
Answer: -We can define evolution as change over time in the frequencies (proportions) of
ditterent alleles in a population. -Gene frequency is the relative frequency of an allele at a
particular locus in a population, expressed as a fraction or percentage. A species evolves
when gene frequency changes over time. -For natural selection to act upon a trait, the trait
must possess heritable variation and confer an advantage for the population.
3. What do genes code for? What are alleles? How is this related to genotype? If
allele frequencies change for a gene in a population, what can be said about that
gene?
Answer: -Genes specify how to build (encode) proteins. -Alleles are one of two forms of a
gene that result in the production of ditterent versions of the protein that the gene encodes.
-Genotype is the genetic makeup of an individual. If a gene has two alleles, designated A and
a, the individual could be of genotype AA, Aa, or aa. -If the frequency of the a allele were to
change over time, from 40% to 71%, then the population would have evolved at that gene.
4. Explain descent with modification using natgive ural selection. What is a vestigial
structure, and how does this support the idea of descent with modification?
Answer: -Descent with modification is the idea that a species change over time, rise to new
species, and share a common ancestor. -A vestigial structure is a feature a species inherited
from an ancestor but is now less elaborate and functional than in the ancestor. This is an
example of descent with modification.
5. Describe why two populations might begin to mental develop different
characteristics. What factors would cause this?
Answer: -Darwin argued that is two populations experience ditterent environconditions,
individuals with one set of characteristics may be favored by natural selection in one
population, while individuals with a ditterent set of characteristics may be favored in the
other population.
6. What is a phenotype? What is it based off of? What causes phenotypes to vary?
Answer: -A phenotype is the observable characteristics of an organism, such as size or color.
-The phenotype of an organism is influenced by its genes. -Individuals ditter from one
another, in part because they have ditterent alleles of genes that influence their phenotype.
Page 1
,7. How do new alleles arise? Is this common?
Answer: -New alleles arise by mutation, a change in the DNA of a gene. -Mutations are
extremely rare.
8. What is recombination? How does it act upon mutation?
Answer: -Recombination is the rearrangement of genetic material during sexual
reproduction that produces ottspring with combinations of alleles that ditter from those in
either of their parents. -We can think of mutation as providing raw material (new alleles) on
which evolution is based, and recombination as rearranging that raw materials into unique
new combinations.
9. What are the three types of natural selection?
a. What is it called when one phenotypic extreme is favored?
b. What is it called when individuals of the intermediate phenotype are favored? -Graphs
c. What is it called when phenotypes of two extremes are favored?
d. Sketch a graph of each type.
Answer: -The three types of natural selection are: a. Directional selection occurs when
individuals with one extreme of a heritable phenotypic trait (e.g., large size) are favored over
other individuals (small and medium-sized individuals). b. Stabilizing selection, when
individuals with an intermediate phenotype (e.g., medium-sized individuals) are favored. c.
Disruptive selection, when individuals with a phenotype at either extreme are favored (e.g.,
small and large individuals have an advantage over medium-sized individuals). are in
Concept 6.2 (Interactive Figure 6.6)
10. What is genetic drift? Is genetic drift an example of natural selection? What
types of populations are more impacted by genetic drift?
Answer: -Genetic drift is when random events attect which alleles are passed from one
generation to the next. It is greater in smaller populations than in large ones. -Genetic drift is
not an example of natural selection, it happens through an entirely random process. -Small
populations are more impacted by genetic drift.
11. What four possible effects can genetic drift have on a population?
a. What is fixation? How does this affect the genetic variation of individuals a population?
b. Why can only mildly deleterious effects increase via genetic drift because and not
terribly deleterious ones? (Hint: What effect might a terribly deleterious allele have an
organism's ability to reproduce? Are allele frequencies still based on random chance in this
case?) because
c. How can genetic drift increase genetic differences between populations?
Answer: -Four possible ettects of genetic drift on a population: 1. Can cause allele
frequencies to fluctuate randomly over time in small populations. Eventually, some alleles
disappear from small populations, while others reach fixation. 2. Genetic drift reduces the
population's genetic variation, making the within the population more similar genetically to
one another. 3. Genetic drift can increase the frequency of a harmful allele. 4. Genetic drift
can increase genetic ditterences between populations random events may cause an allele to
reach fixation in one population yet be lost from another population. -Fixation is when an
allele occurs in a population at a frequency of 100%. Fixation causes low genetic variation in
a population. -Genetic drift can "overrule" the ettects of natural selection, causing a harmful
allele to randomly increase or decrease in frequency. - Genetic drift can increase genetic
ditterences between populations random events may cause an allele to reach fixation in one
population yet be lost from another population.
Page 2
, 12. Which two effects of genetic drift are most detrimental to a population? Why?
Answer: -The second and third ettects can have dire consequences for small populations.
This is because a loss of genetic variation can reduce the capacity of a population to evolve
in response to changing environmental conditions, potentially placing it at risk of extinction.
Likewise, an increase in the frequency of harmful alleles in a population can hinder the ability
of its members to survive or reproduce, again increasing the risk of extinction.
13. What is gene flow? What effects can gene flow have on a population?
Answer: -Gene flow occurs when alleles are transferred from one population to another via
the movement of individuals or gametes. (e.g., plant pollen). -Gene flow has two important
ettects. First, by transferring alleles between populations, it tends to make populations more
similar to one another genetically. Second, gene flow can introduce new alleles into a
population.
14. What is adaption? What features of an ororganism's ganism can be adapted to
the environment?
Answer: -Adaptations are features that evolve by natural selection and improve an ability to
survive and reproduce in its environment. -The features of an organism that can be adapted
to the environment are their structure, physiology, and behavior.
15. Why is natural selection considered to be adaptive evolution? Are traits with an
overall -Traits negative impact selected for by natural sepredictably lection? What
are some examples of adaptive evolution?
Answer: -Natural selection is considered adaptive evolution because it is a process of
change in which traits that confer survival or reproductive advantages tend to increase in
frequency over time. with an overall negative impact are not selected by natural selection.
When natural selection operates, individuals with certain alleles have higher survival and
produce more ottspring than individuals with other alleles. -Natural selection in soapberry
bug populations caused adaptive evolution in which a characteristics of the organism (beak
length) evolved to match an aspect of its environment (fruit size) more closely.
16. What are clines?
Answer: -Clines are patterns of change in a characteristic of an organism over a
geographical region.
17. How have organisms responded to climate change?
Answer: -Organisms have altered their timing of key events in their lives, such as delaying
the onset of winter dormancy or reproducing earlier in the spring.
18. What is phenotypic plasticity?
Answer: -Phenotypic plasticity is the ability of one genotype to produce more than one
phenotype in ditterent environments.
19. How can gene flow lim- -The it adaption? What does it mean to say that adaptive
evolution can only occur if natural selection forces are strong enough to overcome
gene flow?
Answer: extent to which adaptive evolution occurs in each population depends on whether
natural selection is strong enough to overcome the ettects of ongoing gene flow. -Natural
selection and adaptive evolution are driven by ecological interactionsorganisms interacting
with one another and their environment
Page 3
Correct Answers (Verified Update)
107 questions with answers
Topic: PCB 3044 Exam 2 Review (Cook)
1. How does hunting affect natural populations? What is trophy -Trophy hunting, and
how does this change the genetic makeup of the population offspring? What affect
has this had on the ram? What has happened to maturation time in cod? Why?
Answer: -One way hunting attects natural populations is by causing evolutionary change.
hunting is hunting for sport and displaying parts of an animal as trophies. Trophy hunting
causes the genetic characteristics of a population to change, or evolve. -This means rams
with small horns are able to reproduce more frequently than rams with bighorns, resulting in
more small horn rams. -In cod fishery, harvesting practices have selected individuals that
mature at a younger age and a smaller size for production purposes.
2. Define evolution. Explain using gene frequency. What is required of a trait for
natural selection to act upon it?
Answer: -We can define evolution as change over time in the frequencies (proportions) of
ditterent alleles in a population. -Gene frequency is the relative frequency of an allele at a
particular locus in a population, expressed as a fraction or percentage. A species evolves
when gene frequency changes over time. -For natural selection to act upon a trait, the trait
must possess heritable variation and confer an advantage for the population.
3. What do genes code for? What are alleles? How is this related to genotype? If
allele frequencies change for a gene in a population, what can be said about that
gene?
Answer: -Genes specify how to build (encode) proteins. -Alleles are one of two forms of a
gene that result in the production of ditterent versions of the protein that the gene encodes.
-Genotype is the genetic makeup of an individual. If a gene has two alleles, designated A and
a, the individual could be of genotype AA, Aa, or aa. -If the frequency of the a allele were to
change over time, from 40% to 71%, then the population would have evolved at that gene.
4. Explain descent with modification using natgive ural selection. What is a vestigial
structure, and how does this support the idea of descent with modification?
Answer: -Descent with modification is the idea that a species change over time, rise to new
species, and share a common ancestor. -A vestigial structure is a feature a species inherited
from an ancestor but is now less elaborate and functional than in the ancestor. This is an
example of descent with modification.
5. Describe why two populations might begin to mental develop different
characteristics. What factors would cause this?
Answer: -Darwin argued that is two populations experience ditterent environconditions,
individuals with one set of characteristics may be favored by natural selection in one
population, while individuals with a ditterent set of characteristics may be favored in the
other population.
6. What is a phenotype? What is it based off of? What causes phenotypes to vary?
Answer: -A phenotype is the observable characteristics of an organism, such as size or color.
-The phenotype of an organism is influenced by its genes. -Individuals ditter from one
another, in part because they have ditterent alleles of genes that influence their phenotype.
Page 1
,7. How do new alleles arise? Is this common?
Answer: -New alleles arise by mutation, a change in the DNA of a gene. -Mutations are
extremely rare.
8. What is recombination? How does it act upon mutation?
Answer: -Recombination is the rearrangement of genetic material during sexual
reproduction that produces ottspring with combinations of alleles that ditter from those in
either of their parents. -We can think of mutation as providing raw material (new alleles) on
which evolution is based, and recombination as rearranging that raw materials into unique
new combinations.
9. What are the three types of natural selection?
a. What is it called when one phenotypic extreme is favored?
b. What is it called when individuals of the intermediate phenotype are favored? -Graphs
c. What is it called when phenotypes of two extremes are favored?
d. Sketch a graph of each type.
Answer: -The three types of natural selection are: a. Directional selection occurs when
individuals with one extreme of a heritable phenotypic trait (e.g., large size) are favored over
other individuals (small and medium-sized individuals). b. Stabilizing selection, when
individuals with an intermediate phenotype (e.g., medium-sized individuals) are favored. c.
Disruptive selection, when individuals with a phenotype at either extreme are favored (e.g.,
small and large individuals have an advantage over medium-sized individuals). are in
Concept 6.2 (Interactive Figure 6.6)
10. What is genetic drift? Is genetic drift an example of natural selection? What
types of populations are more impacted by genetic drift?
Answer: -Genetic drift is when random events attect which alleles are passed from one
generation to the next. It is greater in smaller populations than in large ones. -Genetic drift is
not an example of natural selection, it happens through an entirely random process. -Small
populations are more impacted by genetic drift.
11. What four possible effects can genetic drift have on a population?
a. What is fixation? How does this affect the genetic variation of individuals a population?
b. Why can only mildly deleterious effects increase via genetic drift because and not
terribly deleterious ones? (Hint: What effect might a terribly deleterious allele have an
organism's ability to reproduce? Are allele frequencies still based on random chance in this
case?) because
c. How can genetic drift increase genetic differences between populations?
Answer: -Four possible ettects of genetic drift on a population: 1. Can cause allele
frequencies to fluctuate randomly over time in small populations. Eventually, some alleles
disappear from small populations, while others reach fixation. 2. Genetic drift reduces the
population's genetic variation, making the within the population more similar genetically to
one another. 3. Genetic drift can increase the frequency of a harmful allele. 4. Genetic drift
can increase genetic ditterences between populations random events may cause an allele to
reach fixation in one population yet be lost from another population. -Fixation is when an
allele occurs in a population at a frequency of 100%. Fixation causes low genetic variation in
a population. -Genetic drift can "overrule" the ettects of natural selection, causing a harmful
allele to randomly increase or decrease in frequency. - Genetic drift can increase genetic
ditterences between populations random events may cause an allele to reach fixation in one
population yet be lost from another population.
Page 2
, 12. Which two effects of genetic drift are most detrimental to a population? Why?
Answer: -The second and third ettects can have dire consequences for small populations.
This is because a loss of genetic variation can reduce the capacity of a population to evolve
in response to changing environmental conditions, potentially placing it at risk of extinction.
Likewise, an increase in the frequency of harmful alleles in a population can hinder the ability
of its members to survive or reproduce, again increasing the risk of extinction.
13. What is gene flow? What effects can gene flow have on a population?
Answer: -Gene flow occurs when alleles are transferred from one population to another via
the movement of individuals or gametes. (e.g., plant pollen). -Gene flow has two important
ettects. First, by transferring alleles between populations, it tends to make populations more
similar to one another genetically. Second, gene flow can introduce new alleles into a
population.
14. What is adaption? What features of an ororganism's ganism can be adapted to
the environment?
Answer: -Adaptations are features that evolve by natural selection and improve an ability to
survive and reproduce in its environment. -The features of an organism that can be adapted
to the environment are their structure, physiology, and behavior.
15. Why is natural selection considered to be adaptive evolution? Are traits with an
overall -Traits negative impact selected for by natural sepredictably lection? What
are some examples of adaptive evolution?
Answer: -Natural selection is considered adaptive evolution because it is a process of
change in which traits that confer survival or reproductive advantages tend to increase in
frequency over time. with an overall negative impact are not selected by natural selection.
When natural selection operates, individuals with certain alleles have higher survival and
produce more ottspring than individuals with other alleles. -Natural selection in soapberry
bug populations caused adaptive evolution in which a characteristics of the organism (beak
length) evolved to match an aspect of its environment (fruit size) more closely.
16. What are clines?
Answer: -Clines are patterns of change in a characteristic of an organism over a
geographical region.
17. How have organisms responded to climate change?
Answer: -Organisms have altered their timing of key events in their lives, such as delaying
the onset of winter dormancy or reproducing earlier in the spring.
18. What is phenotypic plasticity?
Answer: -Phenotypic plasticity is the ability of one genotype to produce more than one
phenotype in ditterent environments.
19. How can gene flow lim- -The it adaption? What does it mean to say that adaptive
evolution can only occur if natural selection forces are strong enough to overcome
gene flow?
Answer: extent to which adaptive evolution occurs in each population depends on whether
natural selection is strong enough to overcome the ettects of ongoing gene flow. -Natural
selection and adaptive evolution are driven by ecological interactionsorganisms interacting
with one another and their environment
Page 3
