Deck 25: Evolutionary Processes

Question 1

Use the following information when answering the corresponding question(s).
In 1983 a population of dark-eyed junco birds became established on the campus of the University of California,San Diego (UCSD),which is located many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains.Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays.Males with more white in their tail are more likely to win aggressive interactions,and females prefer to mate with males with more white in their tails.Females have less white in their tails than do males,and display it less often.(Pamela J.Yeh.2004.Rapid evolution of a sexually selected trait following population establishment in a novel habitat.Evolution 58[1]:166-74. )
Refer to the paragraph on dark-eyed junco birds.The UCSD campus male junco population tails were,on average,36% white,whereas the tails of males from nearby mountain populations averaged 40-45% white.If this observed trait difference were due to a difference in the original colonizing population,it would most likely be due to _____.

A)mutations in the UCSD population
B)sexual selection
C)gene flow between populations
D)a genetic bottleneck
E)a founder effect

Answer 1

E

Question 2

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s.They do not marry with members outside their own immediate community.Today,the Dunkers are genetically unique and differ in gene frequencies,at many loci,from all other populations including those in their original homeland.Which of the following likely explains the genetic uniqueness of this population?

A)population bottleneck and Hardy-Weinberg equilibrium
B)heterozygote advantage and stabilizing selection
C)sexual selection and inbreeding depression
D)mutation and natural selection
E)founder effect and genetic drift

Answer 2

E

Question 3

Use the following information when answering the corresponding question(s).
In 1983 a population of dark-eyed junco birds became established on the campus of the University of California,San Diego (UCSD),which is located many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains.Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays.Males with more white in their tail are more likely to win aggressive interactions,and females prefer to mate with males with more white in their tails.Females have less white in their tails than do males,and display it less often.(Pamela J.Yeh.2004.Rapid evolution of a sexually selected trait following population establishment in a novel habitat.Evolution 58[1]:166-74. )
Refer to the paragraph on dark-eyed junco birds.The UCSD campus male junco population tails are about 36% white,whereas the tails of males from nearby mountain populations are about 40-45% white.The founding stock of UCSD birds was likely from the nearby mountain populations because some of those birds overwinter on the UCSD campus each year.Population sizes on the UCSD campus have been reasonably large,and there are significant habitat differences between the UCSD campus and the mountain coniferous forests;UCSD campus has a more open environment (making birds more visible)and a lower junco density (decreasing intraspecific competition)than that in the mountain forests.Given this information,which of the following evolutionary mechanisms do you think is most likely responsible for the difference between the UCSD and mountain populations?

A)natural selection
B)inbreeding
C)genetic drift
D)gene flow
E)mutation

Answer 3

A

Question 4

Figure 25.2
Use the following information when answering the corresponding question(s)
Martin Wikelski and L.Michael Romero (Body size,performance and fitness in Galápagos marine iguanas,Integrative and Comparative Biology 43 [2003]:376-86)measured the snout-to-vent (anus)length of Galápagos marine iguanas and observed the percent survival of different-sized animals,all of the same age.Figure 25.2 shows the log snout-vent length (SVL,a measure of overall body size)plotted against the percent survival of these different size classes for males and females.

Examine Figure 25.2.What type of selection for body size appears to be occurring in these marine iguanas?

A)directional selection
B)stabilizing selection
C)disruptive selection
D)You cannot determine the type of selection from the above information.

Question 5

Suppose 64% of a remote mountain village can taste phenylthiocarbamide (PTC)and must therefore have at least one copy of the dominant PTC taster allele.If this population conforms to Hardy-Weinberg expectations for this gene,what percentage of the population must be heterozygous for this trait?

A)16%
B)32%
C)40%
D)48%
E)60%

Question 6

Figure 25.1.
Use the following information when answering the following question(s).
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 Figure 25.1.Is this population in Hardy-Weinberg equilibrium?

A)Yes.
B)No;there are more heterozygotes than expected.
C)No;there are more homozygotes than expected.
D)More information is needed to answer this question.

Question 7

Researchers (Helle et al. ,2004)analyzed rates of twin births in the Sami population of Northern Scandinavia during the eighteenth and nineteenth centuries.They found that (1)a baby born from a singleton pregnancy was more likely to survive to adulthood than a baby born from a twin pregnancy,and (2)the average number of offspring raised to adulthood was higher for women who had twins than for those who never had twins.These data suggest that in this population,human twinning rate was _____.

A)under direction selection
B)under stabilizing selection
C)under disruptive selection
D)under sexual selection
E)undergoing genetic drift

Question 8

Genetic drift occurs in a population.Which of the following statements might be true?

A)Genetic drift increased the population's fitness.
B)Genetic drift decreased the population's fitness.
C)The population was relatively small.
D)The population experiences a decrease in genetic variation.
E)Any of the above statements might be true.

Question 9

Wikelski and Romero (2003)found that large marine iguanas had higher reproductive success than smaller iguanas did.However,the large iguanas were generally in poor body condition because they could not eat enough;at higher temperatures their foraging efficiency improved,allowing them to eat more.Thus,Wikelski and Romero hypothesize that iguana size will _____ as global warming gradually increases air and water temperatures in the Galápagos Islands.

A)increase
B)decrease
C)stabilize around the mean body size
D)remain unchanged,it is not clear that body size increases fitness

Question 10

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

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

Question 11

In a small population of alpine foxes,you observe increased ear length over a 10-year period.Can you conclude that increase in ear length is advantageous in this population?

A)Yes
B)No

Question 12

Currently the only predators of Galápagos marine iguanas are Galápagos hawks.Iguana body size is not correlated with risk of hawk predation,although small iguanas can sprint faster than large iguanas.If predators (e.g. ,cats)that preferably catch and eat slower iguanas are introduced to the island,iguana body size is likely to _____ in the absence of other factors;the iguanas would then be under _____ selection.

A)increase;directional
B)increase;disruptive
C)decrease;directional
D)decrease;disruptive
E)stay the same;stabilizing

Question 13

Figure 25.1.
Use the following information when answering the following question(s).
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.

Based on whether the population in Figure 25.1 is in Hardy-Weinberg equilibrium,the researchers had already noted that negligible mutation and migration existed in this milkweed population,and the toxin does not affect the butterflies that pollinate these plants.Which of the following would be a logical conclusion about this milkweed population?

A)Genetic drift and selection are negligible.
B)There is either a heterozygote advantage or stabilizing selection.
C)There is either directional selection or sexual selection.
D)There is either disruptive selection or inbreeding.

Question 14

Cystic fibrosis is a genetic disorder in homozygous recessives that causes death during the teenage years.If 9 in 10,000 newborn babies have the disease,what are the expected frequencies of the dominant (A₁)and recessive (A₂)alleles according to the Hardy-Weinberg model?

A)f(A₁)= 0.9997,f(A₂)= 0.0003
B)f(A₁)= 0.9800,f(A₂)= 0.0200
C)f(A₁)= 0.9700,f(A₂)= 0.0300
D)f(A₁)= 0.9604,f(A₂)= 0.0392
E)f(A₁)= 0.9600,f(A₂)= 0.0400

Question 15

Figure 25.3

Which of the graphs (Fig 25.3)best represents the relationship between the intensity of directional selection and the genetic variation present within a population?

A)Graph A
B)Graph B
C)Graph C
D)Graph D
E)Graph E

Question 16

For a biologist studying a small fish population in the lab,which Hardy-Weinberg condition is easiest to meet?

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

Question 17

A biologist doing a long-term study on a wild spider population observes increased variation in silk thickness.Which of the following could the spider population be experiencing?

A)directional selection
B)stabilizing selection
C)disruptive selection
D)sexual selection
E)genetic drift

Question 18

Three-spined stickleback fish (Gasterosteus aculeatus)show substantial heritable variation in gill-raker length.Fish caught in open water tend to have longer gill rakers and eat different foods than do those caught in shallower water.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 middle and shallow water around the sides)with a high density of these fish?

A)directional selection
B)stabilizing selection
C)disruptive selection
D)sexual selection
E)no selection

Question 19

Use the following information when answering the corresponding question(s).
In 1983 a population of dark-eyed junco birds became established on the campus of the University of California,San Diego (UCSD),which is located many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains.Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays.Males with more white in their tail are more likely to win aggressive interactions,and females prefer to mate with males with more white in their tails.Females have less white in their tails than do males,and display it less often.(Pamela J.Yeh.2004.Rapid evolution of a sexually selected trait following population establishment in a novel habitat.Evolution 58[1]:166-74. )
Refer to the paragraph on dark-eyed junco birds.Which of the following could explain why males display more often?

A)Many male juncos die without fathering any offspring.
B)Females have to expend energy competing for mates.
C)Males are more aggressive than females.
D)energy cost asymmetry in male and female parental investment

Question 20

Cystic fibrosis is a genetic disorder in homozygous recessive (ff)humans that typically causes death in the early 30s.Over time,we would expect the f allele frequency to _____ for this trait.

A)remain the same
B)increase
C)decrease
D)fluctuate

Question 21

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

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 22

In Kerr and Wright's experiment with 96 fruit-fly populations,only 4 males and 4 females bred in each generation.After 16 generations,73% of their populations had only one allele present for the bristle morphology gene.Which of the following would you expect to occur if they allowed 10 males and 10 females to breed in each generation?

A)About 73% of the populations would have only one allele for the bristle morphology gene.
B)More than 73% of the populations would have only one allele present.
C)Less than 73% of the populations would have only one allele present.
D)All of the populations would have only one allele present.

Question 23

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?

A)Mutations 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 24

A beneficial point mutation occurs in a plant ovule,which is fertilized.The seed matures,falls to the ground,and starts to grow.Is the plant's population likely to show evolutionary change as a result of this mutation? Why or why not?

Question 25

A rare species of newt is being studied by a young evolutionary biologist.She observes that female newts lay unusually large yolky eggs,but they abandon their nests as soon as the eggs are laid.Males,on the other hand,defend the territory around the nest and regularly bring the baby newts insects to feed on.The males also sleep with the babies to keep them warmer during cool nights.Which of the following statements is MOST LIKELY to be true of these newts?

A)The males are smaller than the females.
B)The males have lots of bright coloring on their skin to attract females.
C)The females are not choosy about which males to mate with.
D)The males are choosy about which females to mate with.
E)Males have far more offspring than females.

Question 26

In some jacana species,males take care of the eggs and young,and females compete among themselves for territories that contain one to several males.Female jacanas are significantly larger than males.Which of these statements would you predict to be true of this bird species?
1)Male jacana fitness is primarily limited by ability to take care of eggs and raise young.
2)Female jacana fitness is limited by the number of males in her territory with which a female mates.
3)Variation in reproductive success should be greater in male jacanas than in females.
4)Variation in reproductive success should be greater in female jacanas than in males.
5)Males and females have equal variation in reproductive success.

A)1 and 3
B)2 and 4
C)1,2,and 3
D)1,2,and 4
E)5

Question 27

Which sex typically has more extreme sex-selected characteristics:
males or females? Why? Give an example.

Question 28

An earthquake decimates a ground-squirrel population.The surviving population happens to have broader stripes on average than the initial population.If broadness of stripes is genetically determined,what effect has the ground-squirrel population experienced during the earthquake?

A)directional selection
B)disruptive selection
C)a founder event
D)a genetic bottleneck
E)gene flow

Question 29

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.

A)The songs 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 30

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

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 31

Figure 25.4
Refer to Figure 25.4.Male reproductive success,measured as the number of offspring surviving to adulthood (pupating),is found for two closely related beetle species and graphed above.Which of these statements would you expect to be true of sexual dimorphism in the two species?

A)Species A should have greater sexual dimorphism than species B.
B)Species B should have greater sexual dimorphism than species A.
C)Species A and B should have about equal amounts of sexual dimorphism.
D)Neither species should show any sexual dimorphism.

Question 32

Mutation is the only evolutionary mechanism that _____.

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