BSC 114 Chapter 23 Exam Questions
and Answers All Correct
Which statement correctly describes the role of chance in evolution? - Answer-The
ultimate source of new alleles is mutation, random changes in the nucleotide sequences
of an organism's DNA.
The evolutionary effects of genetic drift are greatest when __________. - Answer-the
population size is small
What situation most likely explains the occasional high frequency of certain inherited
disorders among human populations established by a small population? - Answer-
founder effect; is genetic drift attributable to colonization by a limited number of
individuals from a parent population.
Which type of selection tends to increase genetic variation?
a.) Directional selection
b.) Disruptive selection
c.) Stabilizing selection - Answer-b.) Disruptive selection; eliminates phenotypes near
the average and favors the extreme phenotypes, resulting in increased genetic variation
in a population.
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?
a.) Directional selection
b.) Stabilizing selection
c.) Disruptive selection - Answer-a.) Directional selection; drives the average of the
population in one direction, in this case, toward longer necks.
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?
a.) Stabilizing selection
b.) Disruptive selection
, c.) Directional selection - Answer-a.) Stabilizing selection; causes no change in the
average of the population; extreme phenotypes (in this case, large and small babies)
become less common.
Drag each statement into the appropriate bin depending on whether it applies to natural
selection, genetic drift, or gene flow.
-consistently causes a population to become better adapted to its environment
-a result of differential success in reproduction
-cannot cause a harmful allele to become more common - Answer-natural selection
Drag each statement into the appropriate bin depending on whether it applies to natural
selection, genetic drift, or gene flow.
-causes allele frequencies to fluctuate randomly
-can result from the bottleneck effect
-can result from the founder effect - Answer-genetic drift
Drag each statement into the appropriate bin depending on whether it applies to natural
selection, genetic drift, or gene flow.
-can introduce new alleles into a population's gene pool
-a result of the movement of fertile individuals or their gametes - Answer-gene flow
Allele frequencies in a gene pool may shift randomly and by chance. What is this
random shift called? - Answer-genetic drift
If a person has two normal copies of the hemoglobin allele, which statements are true?
Select all that apply.
a.) The person is homozygous at the hemoglobin locus.
b.) The person is heterozygous at the hemoglobin locus.
c.) The person is susceptible to malaria.
d.) The person is protected against malaria. - Answer-a.) The person is homozygous at
the hemoglobin locus.
c.) The person is susceptible to malaria.
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?
a.) Disruptive selection
b.) Stabilizing selection
c.) Directional selection - Answer-a.) Disruptive selection; causes both extreme
phenotypes (large and small beaks) to be favored over the intermediate phenotypes.
and Answers All Correct
Which statement correctly describes the role of chance in evolution? - Answer-The
ultimate source of new alleles is mutation, random changes in the nucleotide sequences
of an organism's DNA.
The evolutionary effects of genetic drift are greatest when __________. - Answer-the
population size is small
What situation most likely explains the occasional high frequency of certain inherited
disorders among human populations established by a small population? - Answer-
founder effect; is genetic drift attributable to colonization by a limited number of
individuals from a parent population.
Which type of selection tends to increase genetic variation?
a.) Directional selection
b.) Disruptive selection
c.) Stabilizing selection - Answer-b.) Disruptive selection; eliminates phenotypes near
the average and favors the extreme phenotypes, resulting in increased genetic variation
in a population.
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?
a.) Directional selection
b.) Stabilizing selection
c.) Disruptive selection - Answer-a.) Directional selection; drives the average of the
population in one direction, in this case, toward longer necks.
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?
a.) Stabilizing selection
b.) Disruptive selection
, c.) Directional selection - Answer-a.) Stabilizing selection; causes no change in the
average of the population; extreme phenotypes (in this case, large and small babies)
become less common.
Drag each statement into the appropriate bin depending on whether it applies to natural
selection, genetic drift, or gene flow.
-consistently causes a population to become better adapted to its environment
-a result of differential success in reproduction
-cannot cause a harmful allele to become more common - Answer-natural selection
Drag each statement into the appropriate bin depending on whether it applies to natural
selection, genetic drift, or gene flow.
-causes allele frequencies to fluctuate randomly
-can result from the bottleneck effect
-can result from the founder effect - Answer-genetic drift
Drag each statement into the appropriate bin depending on whether it applies to natural
selection, genetic drift, or gene flow.
-can introduce new alleles into a population's gene pool
-a result of the movement of fertile individuals or their gametes - Answer-gene flow
Allele frequencies in a gene pool may shift randomly and by chance. What is this
random shift called? - Answer-genetic drift
If a person has two normal copies of the hemoglobin allele, which statements are true?
Select all that apply.
a.) The person is homozygous at the hemoglobin locus.
b.) The person is heterozygous at the hemoglobin locus.
c.) The person is susceptible to malaria.
d.) The person is protected against malaria. - Answer-a.) The person is homozygous at
the hemoglobin locus.
c.) The person is susceptible to malaria.
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?
a.) Disruptive selection
b.) Stabilizing selection
c.) Directional selection - Answer-a.) Disruptive selection; causes both extreme
phenotypes (large and small beaks) to be favored over the intermediate phenotypes.
