Question 1

The recessive allele that causes sickle cell anemia is harmful to homozygous individuals. What maintains the presence of this allele in a population's gene pool?

Accepted Answer

A)  heterozygote advantage 
B)  stabilizing selection 
C)  diploidy 
D)  balancing selection 
A)  heterozygote advantage 
B)  stabilizing selection 
C)  diploidy 
D)  balancing selection

Question 2

Why doesn't inbreeding depression, by itself, cause evolution?

Accepted Answer

A)  It decreases the population's average fitness. 
B)  It limits gene flow. 
C)  It does not change the population's allele frequencies. 
D)  It increases homozygosity. 
E)  It violates the Hardy-Weinberg assumptions. 
A)  It decreases the population's average fitness. 
B)  It limits gene flow. 
C)  It does not change the population's allele frequencies. 
D)  It increases homozygosity. 
E)  It violates the Hardy-Weinberg assumptions.

Question 3

Three-spined stickleback fish (Gasterosteus aculeatus) show substantial heritable variation in gill-raker length related to differences in their diets. Longer gill rakers appear to function better for capturing open-water prey, while shorter gill rakers function better for capturing shallow-water prey. Which of the following types of selection is most likely to be found in a large lake (open water in the middle and shallow water around the sides) with a high density of these fish?

Accepted Answer

A)  directional selection 
B)  stabilizing selection 
C)  disruptive selection 
D)  sexual selection 
A)  directional selection 
B)  stabilizing selection 
C)  disruptive selection 
D)  sexual selection

Question 4

Two frog populations (same species) living in two neighboring lakes sing slightly different courtship songs. Increased irrigation makes the land between the two lakes wetter, allowing frogs to expand their ranges to the area between the lakes. Females in both populations prefer loud frogs to quieter frogs but do not distinguish between the two slightly different songs. Assuming that courtship song differences have a genetic basis, predict what will likely happen to the songs of the two frog populations.

Accepted Answer

A)  The songs will become more similar to each other. 
B)  Males will become louder. 
C)  Disruptive selection will cause the songs to differentiate even more. 
D)  Genetic drift will cause the songs to differentiate even more. 
E)  You cannot predict a change in the courtship songs at the two lakes. 
A)  The songs will become more similar to each other. 
B)  Males will become louder. 
C)  Disruptive selection will cause the songs to differentiate even more. 
D)  Genetic drift will cause the songs to differentiate even more. 
E)  You cannot predict a change in the courtship songs at the two lakes.

Question 5

In all three species of phalarope, a taxon of wading shorebirds, the majority of parental care is provided by the male. Based on the Bateman-Trivers hypothesis of sexual selection, what would you expect to see in phalaropes?

Accepted Answer

A)  Chick survival is very low. 
B)  Females are more brightly colored than males. 
C)  Each female mates with a single male. 
D)  Males are larger than females. 
A)  Chick survival is very low. 
B)  Females are more brightly colored than males. 
C)  Each female mates with a single male. 
D)  Males are larger than females.

Question 6

In 1986, a nuclear power accident in Chernobyl, USSR (now Ukraine), led to high radiation levels for miles surrounding the plant. The high levels of radiation caused elevated mutation rates in the surviving organisms, and evolutionary biologists have been studying rodent populations in the Chernobyl area ever since. Based on your understanding of evolutionary mechanisms, which of the following most likely occurred in the rodent populations following the accident?

Accepted Answer

A)  Mutation caused major changes in rodent physiology over time. 
B)  Mutation led to increased genetic variation. 
C)  Mutation caused genetic drift and decreased fitness. 
D)  Mutation caused the fixation of new alleles. 
A)  Mutation caused major changes in rodent physiology over time. 
B)  Mutation led to increased genetic variation. 
C)  Mutation caused genetic drift and decreased fitness. 
D)  Mutation caused the fixation of new alleles.

Question 7

Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago) and organisms colonized the island, the evolution of life on this new island should have been most strongly influenced by ________.

Accepted Answer

A)  a genetic bottleneck 
B)  sexual selection 
C)  habitat differentiation 
D)  founder effects 
A)  a genetic bottleneck 
B)  sexual selection 
C)  habitat differentiation 
D)  founder effects

Question 8

Which of the following is the most predictable outcome of increased gene flow between two populations?

Accepted Answer

A)  lower average fitness in both populations 
B)  higher average fitness in both populations 
C)  increased genetic difference between the two populations 
D)  decreased genetic difference between the two populations 
E)  increased genetic drift 
A)  lower average fitness in both populations 
B)  higher average fitness in both populations 
C)  increased genetic difference between the two populations 
D)  decreased genetic difference between the two populations 
E)  increased genetic drift

Question 9

Pea aphids (Acyrthosiphon pisum) are the only animals able to synthesize their own carotenoid pigments, due to lateral gene transfer from the genome of a fungus to the genome of a recent ancestor of the pea aphids. The resulting red or green coloration alters the risk the aphids face from specific predators and parasites. Select the correct statement below.

Accepted Answer

A)  The lateral transfer of genes for carotenoid synthesis had a deleterious effect on the aphid genome. 
B)  Natural selection favored the lateral transfer of genes for carotenoid synthesis from a fungus to an aphid. 
C)  The lateral transfer of genes for carotenoid synthesis from a fungus to an aphid is a form of mutation. 
D)  The lateral transfer of genes for carotenoid synthesis occurred to provide the aphids with protection from their predators and parasites. 
A)  The lateral transfer of genes for carotenoid synthesis had a deleterious effect on the aphid genome. 
B)  Natural selection favored the lateral transfer of genes for carotenoid synthesis from a fungus to an aphid. 
C)  The lateral transfer of genes for carotenoid synthesis from a fungus to an aphid is a form of mutation. 
D)  The lateral transfer of genes for carotenoid synthesis occurred to provide the aphids with protection from their predators and parasites.

Question 10

Evolution in a population of island iguanas can be caused by the following agent(s):

Accepted Answer

A)  natural selection. 
B)  genetic drift. 
C)  gene flow. 
D)  All of the above can be agents. 
E)  both natural selection and genetic drift. 
A)  natural selection. 
B)  genetic drift. 
C)  gene flow. 
D)  All of the above can be agents. 
E)  both natural selection and genetic drift.

Question 11

Mutation is the only evolutionary mechanism that ________.

Accepted Answer

A)  is the ultimate source of variation in natural populations 
B)  does little to change allele frequencies 
C)  decreases fitness 
D)  is more important in eukaryotes than in prokaryotes 
E)  has no effect on genetic variation 
A)  is the ultimate source of variation in natural populations 
B)  does little to change allele frequencies 
C)  decreases fitness 
D)  is more important in eukaryotes than in prokaryotes 
E)  has no effect on genetic variation

Question 12

Use the following information to answer the question below.
Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They identify the gene responsible for toxin production. The dominant allele (T) codes for an enzyme that makes the toxin, and the recessive allele (t) codes for a nonfunctional enzyme that cannot produce the toxin. Heterozygotes produce an intermediate amount of toxin. The genotypes of all individuals in the population are determined (see chart) and used to determine the actual allele frequencies in the population.  
Refer to the accompanying figure. Is this population in Hardy-Weinberg equilibrium?

Accepted Answer

A)  Yes. 
B)  No; there are more heterozygotes than expected. 
C)  No; there are more homozygotes than expected. 
D)  It is impossible to tell. 
A)  Yes. 
B)  No; there are more heterozygotes than expected. 
C)  No; there are more homozygotes than expected. 
D)  It is impossible to tell.

Question 13

Natural selection ________.

Accepted Answer

A)  is a random process 
B)  creates beneficial mutations 
C)  completely eliminates harmful mutations 
D)  can favor beneficial mutations 
A)  is a random process 
B)  creates beneficial mutations 
C)  completely eliminates harmful mutations 
D)  can favor beneficial mutations

Question 14

Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer or more than this have reduced fitness. Which of the following terms best describes this situation?

Accepted Answer

A)  artificial selection 
B)  directional selection 
C)  stabilizing selection 
D)  disruptive selection 
E)  sexual selection 
A)  artificial selection 
B)  directional selection 
C)  stabilizing selection 
D)  disruptive selection 
E)  sexual selection

Question 15

Which of the following is most likely to produce an African butterfly species in the wild whose populations show two strikingly different color patterns?

Accepted Answer

A)  artificial selection 
B)  directional selection 
C)  stabilizing selection 
D)  disruptive selection 
E)  sexual selection 
A)  artificial selection 
B)  directional selection 
C)  stabilizing selection 
D)  disruptive selection 
E)  sexual selection

Question 16

Swine are vulnerable to infection by bird flu virus and human flu virus, which can both be present in an individual pig at the same time. When this occurs, it is possible for genes from bird flu virus and human flu virus to be combined. If the human flu virus contributes a gene for Tamiflu resistance (Tamiflu is an antiviral drug) to the new virus, and if the new virus is introduced to an environment lacking Tamiflu, then what is most likely to occur?

Accepted Answer

A)  The new virus will maintain its Tamiflu-resistance gene, in case of future exposure to Tamiflu. 
B)  The Tamiflu-resistance gene will undergo mutations that convert it into a gene that has a useful function in this environment. 
C)  If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency. 
D)  If the Tamiflu-resistance gene confers no benefit in the current environment, and has no cost, the virus will increase in frequency. 
A)  The new virus will maintain its Tamiflu-resistance gene, in case of future exposure to Tamiflu. 
B)  The Tamiflu-resistance gene will undergo mutations that convert it into a gene that has a useful function in this environment. 
C)  If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency. 
D)  If the Tamiflu-resistance gene confers no benefit in the current environment, and has no cost, the virus will increase in frequency.

Question 17

For biologists studying a large flatworm population in the lab, which Hardy-Weinberg condition is most difficult to meet?

Accepted Answer

A)  no selection 
B)  no genetic drift 
C)  no gene flow 
D)  no mutation 
E)  random mating 
A)  no selection 
B)  no genetic drift 
C)  no gene flow 
D)  no mutation 
E)  random mating

Exam 23: Evolutionary Processes

The recessive allele that causes sickle cell anemia is harmful to homozygous individuals. What maintains the presence of this allele in a population's gene pool?

Why doesn't inbreeding depression, by itself, cause evolution?

In all three species of phalarope, a taxon of wading shorebirds, the majority of parental care is provided by the male. Based on the Bateman-Trivers hypothesis of sexual selection, what would you expect to see in phalaropes?

Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago) and organisms colonized the island, the evolution of life on this new island should have been most strongly influenced by ________.

Which of the following is the most predictable outcome of increased gene flow between two populations?

Evolution in a population of island iguanas can be caused by the following agent(s):

Mutation is the only evolutionary mechanism that ________.

Natural selection ________.

Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer or more than this have reduced fitness. Which of the following terms best describes this situation?

Which of the following is most likely to produce an African butterfly species in the wild whose populations show two strikingly different color patterns?

For biologists studying a large flatworm population in the lab, which Hardy-Weinberg condition is most difficult to meet?

Biology and the Tree of Life

Water and Carbon: the Chemical Basis of Life

Protein Structure and Function

Nucleic Acids and the Rna World

An Introduction to Carbohydrates

Ecosystems and Global Ecology

Lipids, Membranes, and the First Cells

Inside the Cell

Energy and Enzymes: an Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

Cellcell Interactions

The Cell Cycle

Meiosis

Mendel and the Gene

Dna and the Gene: Synthesis and Repair

How Genes Work

Transcription, Rna Processing, and Translation

Control of Gene Expression in Bacteria

Control of Gene Expression in Eukaryotes

The Molecular Revolution: Biotechnology and Beyond

Genes, Development, and Evolution

Evolution by Natural Selection

Speciation

Phylogenies and the History of Life

Bacteria and Archaea

Protists

Green Algae and Land Plants

Fungi

An Introduction to Animals

Protostome Animals

Deuterostome Animals

Viruses

Plant Form and Function

Water and Sugar Transport in Plants

Plant Nutrition

Plant Sensory Systems, Signals, and Responses

Plant Reproduction and Development

Animal Form and Function

Water and Electrolyte Balance in Animals

Animal Nutrition

Gas Exchange and Circulation

Animal Nervous Systems

Animal Sensory Systems

Animal Movement

Chemical Signals in Animals

Animal Reproduction and Development

The Immune System in Animals

An Introduction to Ecology

Behavioral Ecology

Population Ecology

Community Ecology

Biodiversity and Conservation Biology

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