Question 1

Which evolutionary process is most likely to increase the proportion of heterozygotes in a population?

Accepted Answer

A)  Natural selection 
B)  Intersexual selection 
C)  Intrasexual selection 
D)  Genetic drift 
E)  Mutation 
A)  Natural selection 
B)  Intersexual selection 
C)  Intrasexual selection 
D)  Genetic drift 
E)  Mutation

Question 2

Muller's ratchet is the

Accepted Answer

A)  breaking down of adaptive combinations of genes by recombination. 
B)  elimination of deleterious mutations through sexual reproduction. 
C)  maintenance of genetic variation via disruptive selection. 
D)  crossing over and independent assortment of chromosomes during meiosis. 
E)  accumulation of deleterious mutations in asexual lineages. 
A)  breaking down of adaptive combinations of genes by recombination. 
B)  elimination of deleterious mutations through sexual reproduction. 
C)  maintenance of genetic variation via disruptive selection. 
D)  crossing over and independent assortment of chromosomes during meiosis. 
E)  accumulation of deleterious mutations in asexual lineages.

Question 3

In a plant population, the genotypes that grow fastest tend to be the most sensitive to drought.This is an example of _______, and it tends to _______ evolution.

Accepted Answer

A)  disruptive selection; accelerate 
B)  disruptive selection; constrain 
C)  stabilizing selection; accelerate 
D)  a trade-off; accelerate 
E)  a trade-off; constrain 
A)  disruptive selection; accelerate 
B)  disruptive selection; constrain 
C)  stabilizing selection; accelerate 
D)  a trade-off; accelerate 
E)  a trade-off; constrain

Question 4

Evolution is most likely to be constrained by

Accepted Answer

A)  sexual dimorphism. 
B)  genetic diversity. 
C)  environmental variation. 
D)  developmental processes. 
E)  neutral alleles. 
A)  sexual dimorphism. 
B)  genetic diversity. 
C)  environmental variation. 
D)  developmental processes. 
E)  neutral alleles.

Question 5

If the exchange of allele b1 for b2 at the b locus does not affect the fitness of individuals, these alleles can be considered _______ alleles.

Accepted Answer

A)  selected 
B)  neutral 
C)  neutered 
D)  Muller's 
E)  deleterious 
A)  selected 
B)  neutral 
C)  neutered 
D)  Muller's 
E)  deleterious

Question 6

Suppose variants at a single locus affect wing length in a species of crickets, with homozygotes for the L allele having long wings, homozygotes for the l allele having short wings, and heterozygotes having wings of intermediate length.In one population of 600 individuals, 400 have long wings, 160 have intermediate-length wings, and 40 have short wings.What is the frequency of the L allele?

Accepted Answer

A)  0.2 
B)  0.35 
C)  0.7 
D)  0.8 
E)  0.96 
A)  0.2 
B)  0.35 
C)  0.7 
D)  0.8 
E)  0.96

Question 7

Evolution by natural selection requires

Accepted Answer

A)  large populations. 
B)  diploid individuals. 
C)  selective breeding by humans. 
D)  genetic variation among individuals. 
E)  small populations. 
A)  large populations. 
B)  diploid individuals. 
C)  selective breeding by humans. 
D)  genetic variation among individuals. 
E)  small populations.

Question 8

Suppose the mutation rate per nucleotide for a genetic locus is 4 × 10-8 and that the locus contains 1,500 nucleotides.What is the per-locus mutation rate?

Accepted Answer

A)  4 × 10-5 
B)  6 × 10-5 
C)  8 × 10-5 
D)  4 × 10-4 
E)  6 × 10-4 
A)  4 × 10-5 
B)  6 × 10-5 
C)  8 × 10-5 
D)  4 × 10-4 
E)  6 × 10-4

Question 9

A genetic locus has two alleles.One has a frequency of 0.12; the other has a frequency of _______.

Accepted Answer

A)  −0.12 
B)  0.12 
C)  0.06 
D)  0.88 
E)  More information is required to answer this question. 
A)  −0.12 
B)  0.12 
C)  0.06 
D)  0.88 
E)  More information is required to answer this question.

Question 10

Suppose a hard frost in southern Florida wipes out nearly all of a population of plants.Even though the plant population recovers in numbers after a couple of decades, the genetic variation within that population remains much reduced.Which is the most likely cause of the diminished genetic variation?

Accepted Answer

A)  Founder effect 
B)  Purifying selection 
C)  Population bottleneck 
D)  Gene flow 
E)  Muller's ratchet 
A)  Founder effect 
B)  Purifying selection 
C)  Population bottleneck 
D)  Gene flow 
E)  Muller's ratchet

Question 11

Was Darwin a specialist or a generalist? Explain in the context of what he did to develop his theory of evolution.

Accepted Answer

Darwin was a generalist in that he was w

Question 12

In a population of tree swallows, 18 individuals are homozygous for the c4 allele, 22 individuals are heterozygous for the allele, and 10 individuals lack the allele.What is the frequency of the c4 allele?

Accepted Answer

A)  0.29 
B)  0.36 
C)  0.40 
D)  0.58 
E)  0.80 
A)  0.29 
B)  0.36 
C)  0.40 
D)  0.58 
E)  0.80

Question 13

Following a flood, migration from neighboring populations alters genotypic frequencies of a population of river bottom midges.Assuming that the conditions for Hardy-Weinberg subsequently will be met, how many generations of random mating will be required to restore the genotypic frequencies to Hardy-Weinberg equilibrium?

Accepted Answer

A)  1 
B)  2 
C)  Between 3 and 10 
D)  Between 11 and 20 
E)  More than 20 
A)  1 
B)  2 
C)  Between 3 and 10 
D)  Between 11 and 20 
E)  More than 20

Question 14

If the frequency of an allele is 0.6, we would expect to find _______ copies of that allele in a population of 1,100 individuals.

Accepted Answer

The answer of If the frequency of an allele is...

Question 15

Which statement about evolution is false?

Accepted Answer

A)  Populations evolve. 
B)  Natural selection is one of several mechanisms of evolution. 
C)  Genetic drift can change the genetic makeup of populations over time. 
D)  Nonrandom mating can change the genetic makeup of populations over time. 
E)  An individual organism will evolve if subject to intense selection. 
A)  Populations evolve. 
B)  Natural selection is one of several mechanisms of evolution. 
C)  Genetic drift can change the genetic makeup of populations over time. 
D)  Nonrandom mating can change the genetic makeup of populations over time. 
E)  An individual organism will evolve if subject to intense selection.

Question 16

Which would not be considered an example of a trade-off?

Accepted Answer

A)  Brightly colored male guppies are more successful at acquiring mates than other males but are more likely to be killed by predators. 
B)  Humans who carry the e4 allele for the Apo-E gene are at greater risk than individuals without this allele for acquiring Alzheimer's disease and coronary heart disease. 
C)  Rats that are resistant to the poison warfarin have an increased need for vitamin K. 
D)  Flies that reproduce early in their lives do not live as long as those that reproduce late. 
E)  Plants of the genus Mimulus that are more resistant to herbivores produce fewer seeds. 
A)  Brightly colored male guppies are more successful at acquiring mates than other males but are more likely to be killed by predators. 
B)  Humans who carry the e4 allele for the Apo-E gene are at greater risk than individuals without this allele for acquiring Alzheimer's disease and coronary heart disease. 
C)  Rats that are resistant to the poison warfarin have an increased need for vitamin K. 
D)  Flies that reproduce early in their lives do not live as long as those that reproduce late. 
E)  Plants of the genus Mimulus that are more resistant to herbivores produce fewer seeds.

Question 17

Which statement about Darwin is true?

Accepted Answer

A)  Even as a youth he recognized that life evolves. 
B)  He published his observations about evolution soon after the HMS Beagle arrived in England. 
C)  He recognized that animals on the Galápagos Islands were all identical to those on the mainland. 
D)  He had a keen interest in geology. 
E)  He was the first to present evidence that life has evolved. 
A)  Even as a youth he recognized that life evolves. 
B)  He published his observations about evolution soon after the HMS Beagle arrived in England. 
C)  He recognized that animals on the Galápagos Islands were all identical to those on the mainland. 
D)  He had a keen interest in geology. 
E)  He was the first to present evidence that life has evolved.

Question 18

A population of frogs of the genus Rana has 126 individuals that are homozygous for one allele, 108 that are heterozygous, and 66 that are homozygous for the other allele.Compared to Hardy-Weinberg expectations, this population has _______ too few heterozygotes.

Accepted Answer

The answer of A population of frogs of the genus...

Question 19

In a bacterial population, the frequencies of two alleles at the same locus remain very constant.In cases where researchers have perturbed the frequencies of the alleles, the frequencies have come back to the same equilibrium point.What is the most reasonable cause of these observations?

Accepted Answer

A)  Clinal variation 
B)  Heterozygote advantage 
C)  Frequency-dependent selection 
D)  Hardy-Weinberg equilibrium 
E)  Genetic drift 
A)  Clinal variation 
B)  Heterozygote advantage 
C)  Frequency-dependent selection 
D)  Hardy-Weinberg equilibrium 
E)  Genetic drift

Question 20

Different populations of mice that were previously isolated now experience gene flow.What is the most likely outcome after several generations?

Accepted Answer

A)  The populations will become more genetically similar to one another. 
B)  The populations will become less genetically similar to one another. 
C)  The total amount of genetic variation across all of the populations will increase. 
D)  The total amount of genetic variation across all of the populations will decrease. 
E)  A founder effect will occur. 
A)  The populations will become more genetically similar to one another. 
B)  The populations will become less genetically similar to one another. 
C)  The total amount of genetic variation across all of the populations will increase. 
D)  The total amount of genetic variation across all of the populations will decrease. 
E)  A founder effect will occur.

Exam 20: Mechanisms of Evolution

Which evolutionary process is most likely to increase the proportion of heterozygotes in a population?

Muller's ratchet is the

In a plant population, the genotypes that grow fastest tend to be the most sensitive to drought.This is an example of _______, and it tends to _______ evolution.

Evolution is most likely to be constrained by

If the exchange of allele b1 for b2 at the b locus does not affect the fitness of individuals, these alleles can be considered _______ alleles.

Evolution by natural selection requires

Suppose the mutation rate per nucleotide for a genetic locus is 4 × 10-8 and that the locus contains 1,500 nucleotides.What is the per-locus mutation rate?

A genetic locus has two alleles.One has a frequency of 0.12; the other has a frequency of _______.

Was Darwin a specialist or a generalist? Explain in the context of what he did to develop his theory of evolution.

In a population of tree swallows, 18 individuals are homozygous for the c4 allele, 22 individuals are heterozygous for the allele, and 10 individuals lack the allele.What is the frequency of the c4 allele?

If the frequency of an allele is 0.6, we would expect to find _______ copies of that allele in a population of 1,100 individuals.

Which statement about evolution is false?

Which would not be considered an example of a trade-off?

Which statement about Darwin is true?

A population of frogs of the genus Rana has 126 individuals that are homozygous for one allele, 108 that are heterozygous, and 66 that are homozygous for the other allele.Compared to Hardy-Weinberg expectations, this population has _______ too few heterozygotes.

In a bacterial population, the frequencies of two alleles at the same locus remain very constant.In cases where researchers have perturbed the frequencies of the alleles, the frequencies have come back to the same equilibrium point.What is the most reasonable cause of these observations?

Different populations of mice that were previously isolated now experience gene flow.What is the most likely outcome after several generations?

Studying Life

Small Molecules and the Chemistry of Life

Proteins, Carbohydrates, and Lipids

Nucleic Acids and the Origin of Life

Cells: the Working Units of Life

Cell Membranes

Cell Communication and Multicellularity

Energy, Enzymes, and Metabolism

Pathways That Harvest Chemical Energy

Photosynthesis: Energy From Sunlight

The Cell Cycle and Cell Division

Inheritance, Genes, and Chromosomes

Dna and Its Role in Heredity

From Dna to Protein: Gene Expression

Gene Mutation and Molecular Medicine

Regulation of Gene Expression

Genomes

Recombinant Dna and Biotechnology

Reconstructing and Using Phylogenies

Speciation

Evolution of Genes and Genomes

The History of Life on Earth

Bacteria, Archaea, and Viruses

The Origin and Diversification of Eukaryotes

Plants Without Seeds: From Water to Land

The Evolution of Seed Plants

The Evolution and Diversity of Fungi

Animal Origins and the Evolution of Body Plans

Protostome Animals

Deuterostome Animals

The Plant Body

Transport in Plants

Plant Nutrition

Regulation of Plant Growth

Reproduction in Flowering Plants

Plant Responses to Environmental Challenges

Physiology, Homeostasis, and Temperature Regulation

Animal Hormones

Immunology: Animal Defense Systems

Animal Reproduction

Animal Development

Neurons, Glia, and Nervous Systems

Sensory Systems

The Mammalian Nervous System: Structure and Higher Functions

Musculoskeletal Systems

Gas Exchange

Circulatory Systems

Nutrition, Digestion, and Absorption

Salt and Water Balance and Nitrogen Excretion

Animal Behavior

The Physical Environment and Biogeography of Life

Populations

Species Interactions

Communities

Ecosystems

A Changing Biosphere

Filters

In a plant population, the genotypes that grow fastest tend to be the most sensitive to drought.This is an example of _, and it tends to _ evolution.

Suppose the mutation rate per nucleotide for a genetic locus is 4 × 10^-8 and that the locus contains 1,500 nucleotides.What is the per-locus mutation rate?