Deck 16: How Populations Evolve

Question 1

Which of the following statements about natural selection are true? Select all that apply.

A)Directional selection occurs when one extreme phenotype in the population is favored.
B)Stabilizing selection favors all phenotypes equally.
C)Disruptive selection favors two extreme phenotypes.
D)Directional selection is most common in stable environments.

Answer 1

A,C TWO OF THE STATEMENTS ARE TRUE.DIRECTIONAL SELECTION OCCURS WHEN ONE EXTREME PHENOTYPE HAS AN ADAPTIVE ADVANTAGE.DISRUPTIVE SELECTION FAVORS TWO EXTREME PHENOTYPES.STABILIZING SELECTION DOES NOT FAVOR ALL PHENOTYPES EQUALLY,INSTEAD IT FAVORS AN INTERMEDIATE PHENOTYPE AND SELECTS AGAINST THE EXTREME PHENOTYPES.DIRECTIONAL SELECTION IS MORE COMMON IN CHANGING ENVIRONMENTS.

Question 2

A certain species of butterfly varies in color from white to dark blue.The birds found in the same area feed on the white or lightly colored butterflies,leaving butterflies that are darkly colored.This is an example of what type of selection?

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

Answer 2

C

Question 3

Variation within a population is maintained by

A)mutation.
B)genetic recombination due to fertilization.
C)gene flow.
D)All of the choices are correct.

Answer 3

D

Question 4

You have been doing extensive research for 30 years on the frequency of coat colors (black,gray,white)in a guinea pig population located in the Andes Mountains.You suspect that your guinea pig population is undergoing stabilizing selection.If this is the case,what would you expect to find when you graph your data? Select all that apply.

A)Two peaks,one at each end of the graph.
B)A graph with a single peak towards the far right.
C)A graph with a single tall and narrow peak located in the center.
D)A graph indicating gray guinea pigs have an advantage over black guinea pigs and white guinea pigs.
E)A graph indicating that gray guinea pigs are being selected against.

Question 5

A random alteration in the sequence of DNA nucleotides that provides a new variant allele is known as a

A)gene mutation.
B)polymorphism.
C)gene frequency.
D)disruption.

Question 6

Which of the following is true about genetic drift?

A)It is more likely to occur in a large population than in a small population.
B)It may lead to an allele becoming fixed in a population.
C)It increases the number of heterozygotes in a population.
D)It increases the frequency of rare alleles in a population.

Question 7

If the Hardy-Weinberg equilibrium is met,what is the net effect?

A)evolution leading to a population better adapted to an unchanging environment
B)evolution leading to a population better adapted to a changing environment
C)very slow and continuous evolution with no increased adaptation
D)no evolution because the alleles in the population remain the same

Question 8

If there is gene flow between two adjacent populations of the same species,then the two populations will

A)have similar gene pools.
B)become isolated from each other.
C)develop into different species.
D)adapt to different conditions and become separate.

Question 9

You are employed by the Natural History Museum of Chicago as a wildlife biologist.You recently completed an expedition to Indonesia where you discovered a new and very colorful species of beetle.Based on observations,you hypothesize that sexual selection may be playing a role in the evolution of this species.Which of the following observations would support your hypothesis?

A)Male beetles are bigger and more brightly colored than females.
B)Female preference for larger,brighter males.
C)Males defend territories.
D)All of the above observations would support your hypothesis.

Question 10

What do the founder effect and the bottleneck effect have in common?

A)Both the founder effect and the bottleneck effect result from mutation.
B)Both the founder effect and the bottleneck effect result from an increase in gene flow.
C)Both the founder effect and the bottleneck effect are examples of disruptive selection.
D)Both the founder effect and the bottleneck effect are forms of genetic drift.

Question 11

Which of these conditions is NOT among the requirements of the Hardy-Weinberg equilibrium?

A)small population
B)no net migration of alleles into or out of the population
C)no net mutations
D)no selection of one phenotype over another
E)random mating population

Question 12

Which statement is NOT true about the founder effect?

A)It is a form of genetic drift.
B)It produces a high frequency of some rare alleles in a small isolated population.
C)Founding members contain a tiny fraction of the alleles found in the original population.
D)The founder effect occurs when a population is subjected to near extinction and then recovers so that only a few alleles are left in survivors.

Question 13

A student proposes that left-handedness is a recessive trait and is hidden in much of the human population.A survey of his class of 36 students finds that 9 students are left-handed.Using the Hardy-Weinberg formula,what would be the expected allelic and genotypic frequencies in this theoretical population?

A)P =.27 q =.09;
P² =.07,2pq =.048,q²=.00479
B)P =.5 q =.5;
P² =.25,2pq =.50,q²=.25
C)P =.75 q =.25;
P2 =.56,2pq =.25,q2=.25
D)They cannot be estimated using these limited data.

Question 14

Mutations that result in resistance to specific antibiotics in bacterial organisms occur

A)only when the bacteria are exposed to the drug to which they become resistant.
B)more often when the bacteria are exposed to the drug.
C)at any time,even when the bacteria are not exposed to the drug.
D)only when the bacteria are exposed to radiation or other mutagens.

Question 15

Which of the following would change the allele frequencies of a population?

A)Lack of mutation in the DNA
B)Tall people in a population preferentially marry other tall people.
C)A population on an island remains isolated and no one leaves or moves onto the island.
D)All of the answer choices would change allele frequencies of a population.

Question 16

The most common source of genetic variation in sexually reproducing organisms is

A)mutation.
B)recombination of alleles through meiosis and fertilization.
C)duplication of chromosomes.
D)duplication of genes.

Question 17

Which of the following is/are a biological "population?"

A)all of the corn plants in a cornfield
B)all of the variable-colored ladybird beetles of the species Harmonia axyridis in a forest
C)all male and female English sparrows that reside in your community
D)all of the human population of a rural western town
E)All of the choices are correct.

Question 18

The recessive allele for sickle cell anemia is more prevalent in regions of Africa where malaria is prevalent,than it is in regions where there is no malaria.This is due to

A)heterozygous advantage.
B)founder effect.
C)frequency dependent selection.
D)bottleneck effect.

Question 19

What is the term used to describe the changes in allele frequencies of a population over generations?

A)genetic drift
B)founder effect
C)microevolution
D)directional selection

Question 20

All the members of a single species that occupy a particular area at the same time are known as a

A)subspecies.
B)gene pool.
C)population.
D)group.
E)sub-population.

Question 21

A dominant allele is found in a population with a frequency of 0.8.As the environment begins to change,the dominant allele is not favored.Scientists find that the frequency of the dominant allele decreases by half each generation.What are the allele,genotype,and phenotype frequencies before and one generation after the population begins to change? Is Hardy-Weinberg equilibrium maintained?

Question 22

Define and give an example of assortative mating.Will this affect genotype frequencies?

Question 23

Scientists have studied,in detail,the evolution of the peppered moth,Biston betularia,over the last two hundred years.The peppered moths rest on tree trunks and are a tempting treat for birds in the area.In the mid-1800s the trees in their England habitat were covered with lichens,which are a light,grayish-green color.Although color variations occurred,the vast majority of the moths were light-colored.Because their light coloration effectively camouflaged them against the lichens-covered trees,they were not as easily seen by birds as darker colored moths.The light-colored moths flourished.
The environment changed,as the Industrial Revolution progressed.By 1900,the lichens had died and trees were coated with soot due to industrial pollution.The lighter colored moths were no longer "hidden" in their environment,and in fact,were easily seen by their predators.Their numbers dwindled.At the same time,the darker-colored moths flourished because of their ability to hide on the soot-covered trees.
a.What type of selection is this?
b.What is the agent of selection?
c.What alleles were favored in the clean environment? The polluted environment?

Question 24

Social research indicates that a person is most likely to marry someone from the same village or city,or a high school or college classmate.Therefore,the Hardy-Weinberg equilibrium does not apply well to human populations because

A)there is limited gene flow in the human population.
B)selection of mates is random.
C)individuals are not pairing up by chance across the whole population.
D)the human population is small.
E)natural selection is shaping mate choice in humans.

Question 25

What is the relative biological fitness of an individual who is heterozygous for sickle-cell disease who lives in central Illinois vs.an individual who is heterozygous and lives in South Africa?

Question 26

The northern elephant seal was hunted almost to extinction during the 18th and 19th centuries.Less than 100 seals were left to contribute to the gene pool of their future generations.Since the early 20th century,the elephant seals have been protected by law in both the U.S.and Mexico.Over 100,000 seals now inhabit the western shores of North America,all related to the small population that survived the slaughter of hunters. Scientists fear the elephant seals may be more susceptible to disease and pollution due to

A)heterozygous advantage.
B)disruptive selection.
C)founder effect.
D)bottleneck effect.

Question 27

You have been studying a newly discovered species of lemur.You have established that sexual selection has been a powerful force in the evolution of this species and it is clear that female choice plays an important role in determining which males procure mates.After many hours of observation and data collection,you find that females prefer males that are more proficient at collecting sap and fruit.You should conclude that your data strongly supports the good genes hypothesis.

Question 28

Which of the following is required for natural selection to occur in a population?

A)heritable variation
B)accumulation of adaptive traits
C)differential reproduction
D)All of the choices are correct.

Question 29

Scientists have studied,in detail,the evolution of the peppered moth,Biston betularia,over the last two hundred years.The peppered moths rest on tree trunks and are a tempting treat for birds in the area.In the mid-1800s the trees in their England habitat were covered with lichens,which are a light,grayish-green color.Although color variations occurred,the vast majority of the moths were light-colored.Because their light coloration effectively camouflaged them against the lichens-covered trees,they were not as easily seen by birds as darker colored moths.The light-colored moths flourished.
The environment changed,as the Industrial Revolution progressed.By 1900,the lichens had died and trees were coated with soot due to the industrial pollution.The lighter colored moths were no longer 'hidden' in their environment,and in fact,were easily seen by their predators.Their numbers dwindled.At the same time,the darker-colored moths flourished because of their ability to hide on the darkened trees.
Describe what the initial normal population curve would look like before pollution.Describe what the population curve would look like after the Industrial Revolution and indicate what phenotype was favored.

Question 30

The difference in temperature preference between two populations of Daphnia water fleas is due to a mutation.The original population prefers temperatures near 20°C,while the mutant population prefers temperatures between 25°C and 30°C.Predict how natural selection might affect the geographical distribution of these two populations.

Question 31

A population was surveyed to determine the percentage of individuals with detached earlobes and attached earlobes.16% of the population was found to have attached earlobes,a trait coded for by a recessive allele.Calculate the allele,genotype and phenotype frequencies of the population,assuming Hardy-Weinberg equilibrium is maintained.

Question 32

If the small groups of Viking explorers in Greenland and North America had survived and given rise to new populations,such a scenario would be an example of

A)gene flow from continent to continent.
B)the bottleneck effect.
C)genetic drift among the original Viking explorers.
D)directional selection.
E)the founder effect.

Question 33

In a population,the allele frequency for red flower color remained at 0.7 and the allele frequency for white flower remained at 0.3 for six generations.This ________ an example of a Hardy-Weinberg equilibrium in that ________.

A)is not; evolution occurred
B)is; evolution did not occur
C)is; evolution occurred
D)is not; evolution did not occur

Question 34

Natural selection can maintain genetic variation by favoring heterozygous genotypes.In equatorial Africa,the best genotype to have for hemoglobin is heterozygous (HbA / HbS).In the United States,there is no advantage to the heterozygous genotype.HbA codes for normal hemoglobin,whereas HbS codes for abnormal hemoglobin that causes red blood cells to become distorted in shape (sickle cell).Explain why the heterozygous state is advantageous in Africa,but not in the United States.What has happened to the sickle-cell allele in Africa? What has happened to the sickle-cell allele in the United States?

Question 35

The black bellied seed cracker,Pyrenestes,is a West African finch.Within the same geographic region,two subspecies of the finch are found.One subspecies has a large beak,which is efficient at cracking the hard seeds of the sedge,Scleria verrucosa.The other subspecies has a small beak,which is more efficient at eating the soft seeds of the sedge,Scleria goossensii.What type of selection occurred to produce this situation? Explain what a population distribution graph would look like that would depict this type of selection.

Question 36

Over the course of millions of years various environments have changed.As grasslands slowly took the place of forests the inhabitants were forced to adapt or they went extinct.During this time period the horse gradually evolved from a small cat sized creature to the size of the modern horses we see today.This is an example of which type of natural selection?

A)directional
B)disruptive
C)stabilizing
D)artificial
E)drift

Question 37

In the case of the peppered moths in England,when Kettlewell set up cameras to document that more white or black moths were eaten by birds on clean or sooty trees,he was verifying which factor involved in evolution by natural selection?

A)The organisms vary in traits and that these traits may be acquired during a lifetime.
B)The variation is inherited.
C)More young are born than can survive,so there will always be competition.
D)Some individuals are better adapted to a particular environment than other individuals.

Question 38

Amish populations in Lancaster County,Pennsylvania have high rates of a rare form of dwarfism.The recessive allele that codes for this disorder is found in 1 of 14 individuals in this Amish population,in contrast to 1 in 1,000 in the general population.In Ohio,an Amish population suffers with higher than normal rates of cystic fibrosis and a host of other genetic diseases so rare that some have not yet been named.What factors have caused such severe genetic problems in these two communities?

Question 39

Hospital data shows that human infants born with an intermediate birth weight have a better chance of survival than those that weigh much less or much more.Larger than normal babies may have a difficult delivery,while smaller than normal babies may not be fully developed.What type of selection is occurring? Is the variability in birth weight in human populations increasing or decreasing?

Question 40

If the mutation rate of individual genes is taken to be about one in 100,000 genes per cell cycle across many organisms,we might expect evolution to proceed at a consistent rate for various forms of life.Which factor could make the accumulation of gene mutations faster or slower among different organisms?

A)Organisms with more genes will likely have more mutations per generation.
B)More selection of mutations can occur in a shorter period of time for bacteria that replicate each twenty minutes than for humans with a (roughly)20-year generation span.
C)Organisms vary in the percent of loci that have multiple alleles.
D)Some organisms may be more effective at repairing mutations before they are passed on to the next generation.
E)All of the choices are correct.

Question 41

Which of the following conditions is necessary to maintain the Hardy-Weinberg equilibrium?

A)random mating
B)mutations
C)sexual selection
D)gene flow
E)genetic drift

Question 42

Explain why male baboons have evolved to be larger than the females of the species.

Question 43

Which of the following conditions is not necessary to maintain the Hardy-Weinberg equilibrium?

A)large gene pool
B)no migration
C)mutation
D)random mating
E)no selection

Question 44

Members of a population of guinea pigs exhibit one of three possible coat colors: black,gray,or white.Due to habitat loss,the population has recently colonized a new environment that has areas of black rocks as well as areas of white rocks.In addition,this new habitat contains several predators.If you could visit this population several generations later,what kind of phenotypic pattern,in terms of coat color,would you expect to find in this population?

A)Most guinea pigs would be white.
B)Most guinea pigs would be black.
C)Most guinea pigs would be gray.
D)Most guinea pigs would be either black or white.
E)There would be no difference in the frequency of coat colors.

Question 45

Gene mutation occurs at any time,without respect to the mutation's adaptive value or benefit to the organism.

Question 46

Which of the following likely reflects the presence of one or more gene mutations?

A)Fruit flies subjected to intense radiation produce a wider array of variable offspring.
B)A chemical leaking from the surface of an old abandoned coal mine alters a regulatory gene so that a cricket nymph develops an extra set of eyes.
C)The bacteria that cause gonorrhea,a common sexually transmitted disease,have previously been killed by penicillin; however,after continuous usage of the antibiotic,penicillin-resistant strains are now becoming prevalent.
D)Radiation causes an alteration in a DNA nucleotide sequence,which is discovered when mapped,but which appears to be neither increasing nor decreasing in successive generations.
E)All of the choices are correct.

Question 47

The founder effect is an example of genetic drift in which rare alleles occur at a higher frequency in a population isolated from the general population.

Question 48

British land snails are an example of disruptive selection.In the grassy fields,the light-banded snails escape bird predators.In the darker forest,the dark snails survive and the light-banded snails are eaten.The different colored snails have the opportunity to interact and breed across the British landscape.Why doesn't this "disruptive selection" eventually lead to two separate species?

A)There is no reproductive isolation to prevent gene flow.
B)They are already two separate species,and the intermediate forms are hybrids.
C)The color forms are probably not genetically determined.
D)This will result in the formation of two species if given a long enough time.

Question 49

The bottleneck effect is thought to be responsible for the loss of genetic variability in certain populations.

Question 50

Dominant alleles are always the most common alleles in a population.

Question 51

Which of the following agents of evolution will help a population become better adapted to its environment?

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

Question 52

At the beginning of a research project on egg laying in seagulls,a researcher noted that the birds laid an average of 7-9 eggs per clutch.After studying the population for 15 generations,the researcher noted that the birds were now laying 3-4 eggs per clutch.What type of natural selection is occurring in the population of gulls?

A)stabilizing
B)directional
C)disruptive
D)There is no selection occurring in this population.

Question 53

Which genotype is most likely to survive in a region of the world that contains malaria?

A)homozygous recessive for hemoglobin shape
B)heterozygous for hemoglobin shape
C)homozygous dominant for hemoglobin shape
D)All genotypes have the same potential for survival in a region that contains malaria.

Question 54

A population of organisms that reproduce asexually will display more variation than a population that reproduces sexually.

Question 55

What is the most plausible explanation for why the male of most bird species have elaborate plumage and mating rituals?

A)sexual selection
B)genetic drift
C)gene flow
D)natural selection