Deck 25: Evolutionary Processes

Question 1

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 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

Answer 1

C

Question 2

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)stay the same
D)vary more

Answer 2

A

Question 3

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.

Answer 3

A

Question 4

Cystic fibrosis is a genetic disorder in homozygous recessives (ff)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 5

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

Question 6

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 7

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

Question 8

Based on the information given above,which of the following types of selection was most likely initially involved in the evolution of white outer tail feathers in juncos?

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

Question 9

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

Question 10

A biologist doing a long-term study on a wild spider population observes increased variation in silk thickness.She hypothesizes that the population is experiencing

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

Question 11

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)Two of the above statements might be true.
E)Any of the above statements might be true.

Question 12

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 13

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

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 15

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 be due to

A)disruptive selection.
B)sexual selection.
C)sexual dimorphism.
D)a genetic bottleneck.
E)founder effect.

Question 16

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 17

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;stabilizing
E)stay the same;stabilizing

Question 18

Figure 25.1 Use the following information when answering the corresponding 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 19

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. 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.

Figure 25.2
Examine the figure above.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)sexual selection

Question 20

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 21

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 22

Given the information about the number of individuals of specific genotypes in the table above,what can you infer?

A)A₂ is the dominant allele.
B)The relative amounts of each allele.
C)The phenotype of the individuals with each genotype.
D)The phenotype of A₁ is likely disadvantageous.

Question 23

Given the information above,what is the frequency of individuals with the A₁A₁ genotype?

A)0)1
B)0)15
C)0)2
D)0)3
E)0)4

Question 24

Which of the following is true?

A)Hardy-Weinberg can be used to examine only 1 gene at a time.
B)Hardy-Weinberg considers an organism's entire genotype (all genes).
C)Hardy-Weinberg can be used to examine more than 1 gene at a time.

Question 25

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

Question 26

Figure 25.4
Male turkeys have a snood,a flap of skin that hangs across their beak.Snood length is negatively correlated with parasite load (e.g.,males with longer snoods have fewer parasites),and females prefer to mate with long-snooded males.This is an example of

A)the fundamental asymmetry of sex.
B)sexual selection via female choice.
C)sexual selection via male-male competition.
D)a genetic marker.

Question 27

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 each in 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 28

Figure 25.4
This chapter's essay explains that the membrane protein involved in cystic fibrosis confers resistance to typhoid fever.Imagine that a drug-resistant form of typhoid fever becomes common worldwide,killing a significant proportion of the human population over a period of several decades.Which of the following would you expect to observe in the world population during this period?

A)no change in the frequency of cystic fibrosis
B)decrease in the frequency of cystic fibrosis
C)increase in the frequency of cystic fibrosis

Question 29

Two frog populations (same species)living in two neighboring lakes sing slightly different courtship songs.Predict what likely happens to the songs of the two frog populations after increased irrigation makes the land between the two lakes wetter.Females prefer loud frogs to quieter frogs,but do not distinguish between the two slightly different songs.Assume that courtship song differences have a genetic basis.

A)The songs become more similar to each other.
B)The songs become more different from each other.
C)There is no change in the frog courtship songs of the two lakes.

Question 30

Mutation is the only evolutionary mechanism that

A)does little to change allele frequencies on its own.
B)always causes decreased fitness.
C)is more important in eukaryotes than in prokaryotes.
D)is not mentioned by the Hardy-Weinberg model.
E)has no effect on genetic variation.

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

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 33

In some jacana species,males take care of the eggs and young,and females compete for territories and males against one another.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 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 34

In 1986,a nuclear power accident in Chernobyl,USSR (now the 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)Mutation by itself led to 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 35

If an allele is found at a frequency of 0.8 in a population that is in Hardy-Weinberg equilibrium,and an individual is heterozygous for that allele,what is the probability they will pass on that allele to their offspring?

A)0)8
B)0)2
C)0)5
D)0)64

Question 36

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 37

The frequency of theB₁ allele (for an autosomal gene)in a population that is in Hardy-Weinberg equilibrium is 0.2 and the frequency of the B₂ allele is 0.8.The phenotype of allele B₁ is dominant to that of B₂.If females make up exactly half of the population,what is the frequency of the B₁ allele in the female population alone?

A)0)1
B)0)2
C)0)4
D)0)8

Question 38

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 39

Which of the following describes what we should expect when a population is in Hardy-Weinberg genetic equilibrium?

A)a sexually reproducing population that is increasing in size
B)an asexually reproducing population that is increasing in size
C)a sexually reproducing population that is not evolving
D)an asexually reproducing population that is not evolving
E)a sexually reproducing population that is evolving.

Question 40

Given the information above,what is the frequency of the A₂ allele in this population?

A)0)75
B)0)8
C)0)85
D)0)875
E)0)9

Question 41

A hurricane sweeps across the southern tip of Florida,killing salamanders randomly.Salamander colour is genetic,and,after the storm,scientists notice that the frequency of yellow-brown salamanders and green-brown salamanders has changed significantly.This is an example of a ________ and we would predict that 20 generations after the storm the population would show ________.

A)founder effect;a lot of genetic variation
B)founder effect;speciation
C)founder effect;little genetic variation
D)bottleneck effect;little genetic variation
E)bottleneck effect;many useful adaptations to surviving floods

Question 42

Which of the following best describes the effect of the migration of individuals into a population?

A)Migration of individuals into a population generally increases the genetic variability within the recipient population.
B)Migration of individuals into a population generally causes no change in the genetic variability within the recipient population because it is a case of artificial selection.
C)Migration of individuals into a population generally causes the recipient population to diverge so much that it becomes a new species.
D)Migration of individuals into a population generally decreases the genetic variability within the recipient population.
E)Migration of individuals into a population generally increases the genetic variability within the donor population.

Question 43

Speller et al.(2010)analyzed turkey mitochondrial DNA haplotypes and reported that turkeys were domesticated by precontact native North American cultures in several independent events.Which of the following would be evidence of domestication of turkeys?

A)High genetic variation in turkey tissues found at settlement sites compared to wild turkey tissues.
B)Low genetic variation in wild turkeys relative to turkey tissues found at the settlement sites.
C)Low genetic variation in turkey tissues found at settlement sites compared to wild turkey tissues.
D)Similar amounts of genetic variation in wild turkeys relative to turkey tissues found at the settlement sites.

Question 44

Which of the following is FALSE with respect to natural selection and genetic drift?

A)Both natural selection and genetic drift result in allele frequency changes.
B)Both natural selection and genetic drift involve differences in fitness.
C)Both natural selection and genetic drift require genetically inherited traits.

Question 45

A population of 500 field mice exhibits black or grey coat colours in approximately equal proportions.An individual mouse has a mutation that results in a brown coat colour;this mutation is passed along to many of its 20 offspring,who also exhibit a brown phenotype.If frequency-dependent selection is operating,which of the following would be true?

A)Mice within the population would breed nonrandomly to avoid inbreeding depression.
B)Mice with the brown phenotype would have a higher fitness relative to individuals with black or grey coat colour.
C)Mice with the brown phenotype would have a lower relative fitness to individuals with black or grey coat colour.
D)Mice with the brown phenotype would have higher relative fitness if they were heterozygous.
E)There would be more heterozygous individuals in the population than expected according to HWE. F)It is impossible to determine unless the type of selection is known.

Question 46

How do the founder effect and the immigration aspect of gene flow differ for the cheetah (Acinonyx jubatus)?

A)Gene flow involves cheetahs moving into an area with an established cheetah population,whereas founder effect involves cheetahs colonizing an area where there is no established cheetah population (but where there might be populations of other species).
B)Both gene flow and founder effect involve cheetahs moving into established populations of cheetahs.
C)Gene flow involves cheetahs moving into an area with an established population of another species (e.g.,lions),whereas founder effect involves cheetahs moving into an area where there is an established cheetah population.
D)Both gene flow and founder effect involve cheetahs moving into an area where there is no established cheetah population.

Question 47

In a population of parrots on an island,there is considerable variation in beak size.Parrots with small,thick beaks can efficiently eat locusts (insect),while birds with long,thin beaks can efficiently eat beetles.Both food types are available on the island.Which of the following types of selection,and effects on phenotypic variation would you expect to see?

A)Directional selection;phenotypic variation decreases.
B)Directional selection;phenotypic variation increases.
C)Disruptive selection;phenotypic variation decreases.
D)Disruptive selection;phenotypic variation is maintained.
E)Directional selection;phenotypic variation remains the same.

Question 48

Dark-eyed junco birds have white outer tail feathers that the males display during aggressive interactions and also during courtship displays.Males with more white in their tail are more likely to win aggressive interactions with other males,and females prefer to mate with males with more white in their tails.In the case of juncos,aggression (fighting)by males is a type of ________ selection;thus,we would expect that variation in reproductive success to be higher in ________ and this species should exhibit ________ sexual dimorphism.

A)intrasexual;males;greater
B)intersexual;males;less
C)intrasexual;males;less
D)intersexual;females;greater
E)intrasexual;females;greater

Question 49

Humans have domesticated a number of plants and animals.In the domestication process,a few individuals of a species are "captured" to have a starting population and then these are bred for many generations.This is an example of a ________ and you would therefore predict that domesticated organisms would show ________.

A)founder effect;a lot of genetic variation
B)bottleneck effect;little genetic variation
C)bottleneck effect;many useful adaptations for surviving floods
D)gene flow;speciation
E)founder effect;little genetic variation

Question 50

Consider the following two scenarios: 1)A flash-flood sweeps through an area and random lemmings are killed,resulting in a change in lemming phenotype in subsequent generations;2)A flash-flood sweeps through an area and some lemmings are able to survive because they are able to hold their breath longer than other lemmings,resulting in a change in lemming phenotype in subsequent generations.What are the primary differences between the two scenarios?

A)Scenario 1 represents genetic drift because changes in the population were not adaptive,while Scenario 2 represents natural selection because some individuals were better adapted than other individuals.
B)Scenario 1 represents natural selection because changes in the population were adaptive,while Scenario 2 represents genetic drift because changes in the population were due to higher fitness of some individuals.
C)Both scenarios represent genetic drift because the flash-flood is a random event.
D)Both scenarios represent natural selection because some individuals survived in each scenario.