Evolution exam 2 (QUESTIONS)

Imagine a widely distributed mammal species for which body size shows strong heritability and follows Bergmann's rule. Predict the outcome if efficient predators that live in warm regions preferentially attack large individuals.

a. Evolution of smaller body sizes across the entire range

b. Evolution of larger body sizes across the entire range

c. Evolution of a cline, with large bodied individuals in the south and small bodied individuals in the north

d. Evolution of a cline, with large bodied individuals in the north and small bodied individuals in the south

e. Extinction of the mammal, as too many stresses cannot be handled at once

d.

Which condition would result in the least evolution as a result of gene flow?

a. Unusually high migration variance

b. A great dispersal distance between birth and mating

c. Individuals that are very successful at migrating to new populations, but cannot mate in the new locations

d. Migration rates that vary greatly from year to year

e. Very different allele frequencies in different subpopulations

c.

You observe a very narrow cline in the middle of a broadly distributed species' range. From this you could conclude that

a. selection is strong.

b. migration variance is high.

c. migration variance is low.

d. Either a or b

e. Either a or c

e.

Which scenario would be found in a tension zone of a cline?

a. Natural selection eliminates heterozygotes, preventing introgression deep into the other side of the cline.

b. There are differing selection pressures on either side of the cline.

c. There is strong gene flow, relative to selection.

d. Selection is weak but the cline is maintained by low dispersal rates.

e. Local adaptation has led to a very low FST between either end of the cline.

a.

Which organism depends most on high rates of dispersal and migration for survival of its population?

a. An annual wildflower that colonizes disturbed patches

b. An insect that depends on a very specific flower for nectar meals

c. A freshwater fish that lives in an ancient lake

d. An island population of bats

e. A domesticated animal, like a cow or a sheep

a.

Which factor is least likely to limit dispersal to a new range of an organism whose environment is changing?

a. The rea of suitable habitat has decreased outside of original range.

b. Impassable barriers to movement exist.

c. Organism is physiologically incapable of surviving elsewhere.

d. Organism is a relatively poor disperser.

e. Organism has a generalist diet and can find food in many habitats.

e.

Many North American animal species migrated to the south during Pleistocene ice ages and returned to the north during interglacial periods. These observations are consistent with

a. expanded physiological tolerance.

b. distribution shift and habitat tracking.

c. migration barriers.

d. range expansion by adaptation.

e. declining habitat size.

b.

Which source of variation is most important to evolution?

a. Genetic change

b. Maternal effect

c. Environmental variance

d. DNA methylation

e. Developmental noise

a.

Which observation about a population would not violate the assumptions of the Hardy-Weinberg principle?

a. UV radiation induces new mutations at a high frequency.

b. Individuals migrate from nearby populations but die prior to breeding.

c. Cold tolerance differs by genotype, and the population experiences a frost.

d. Inbreeding is present.

e. The population size is smaller than 100 individuals.

b.

Nonrandom associations between alleles at different loci are referred to by which term?

a. Heterozygosity

b. Linkage equilibrium

c. Inbreeding depression

d. Panmictic

e. Linkage disequilibrium

e.

A mutation in DNA found in which type of cell would be found in descendants as well as the individual in which the mutation occurred?

a. A guard cell in a leaf's stomata

b. A skin cell on a monkey's ear

c. A germ-line cell in an elephant's teste

d. A muscle-cell in a mouse's heart

e. A parenchyma cell in the soft tissue of a plant's fruit

c.

When we say that mutation is random, we mean that

a. we cannot predict which gene copy will undergo a mutation, and environments do not induce adaptive mutations.

b. all loci are equally mutable.

c. the chance that a mutation occurs is influenced by whether or not an organism is in an environment in which that mutation would be advantageous.

d. environmental factors cannot affect mutation rates.

e. all conceivable mutations are equally likely to occur.

a.

Phenotypic differences that are not based on DNA sequence differences (for example, DNA methylation) can be passed from parent to offspring. This phenomenon is called

a. genotype × environment interaction.

b. maternal effects.

c. epigenetic inheritance.

d. phenotypic plasticity.

e. norm of reaction.

c.

Natural selection and genetic drift are the two most important causes of evolutionary change. How do they differ?

a. Natural selection focuses on the survival of individuals, while genetic drift refers to which individuals actually reproduce.

b. Only genetic drift has been observed in populations of finite size.

c. Only natural selection can change the frequencies of alleles in a population.

d. Natural selection involves a population moving toward a goal, while genetic drift is not directed.

e. Genetic drift is nonadaptive; it changes allele frequency without regard to fitness.

e.

Consider a hypothetical locus with several segregating alleles. The population size is small, mutation is absent, and none of the alleles has a selective advantage. Which of the following is likely to occur after a long period of time (many generations)?

a. Balancing selection will maintain all the alleles.

b. Genetic variation will decline as alleles randomly go extinct.

c. Allele frequencies will change over time, but all alleles will remain.

d. Allele frequencies will remain constant.

e. Allele frequencies will cycle over time.

b.

Two alleles segregate at a locus. Assuming that no stabilizing forces exist, the first allele will eventually be _______.

a. either lost or found.

b. either lost or fixed.

c. preserved.

d. fixed.

e. either fixed or broken.

b.

In the late eighteenth century, a typhoon swept through the Pacific atoll of Pingelap, leaving approximately 20 survivors. A large percentage of the present-day inhabitants of Pingelap are color blind. One can conclude, therefore, that the population experienced a _______.

a. bottleneck.

b. selective sweep.

c. coalescence.

d. speciation event.

e. mutation.

a.

Which observation would be the best evidence for a recent founder event or population bottleneck?

a. Low genetic diversity in a single population of a widely distributed species

b. Evidence that population size on an island is maintained by a steady influx of migrants from the mainland

c. Roughly equal genetic variation in all subregions of a species range

d. Evidence that a specific genotype has a strong selective advantage in an environment

e. Census evidence for a steadily growing population

a.

Which statement about genetic drift is true?

a. Linkage disequilibrium cannot occur, because of genetic drift.

b. Evolution by random genetic drift proceeds faster in large populations than in small populations.

c. New mutations that are neutral are less likely to be fixed in small populations than in large populations.

d. Heterozygosity is unaffected by genetic drift.

e. Mildly disadvantageous alleles can sometimes increase in frequency, due to genetic drift.

e.

Which mutation is most likely to become fixed?

a. All of these mutations are equally likely to be fixed.

b. A beneficial mutation in an extremely large population

c. A neutral or nearly neutral mutation in an extremely small population

d. A neutral or nearly neutral mutation in an extremely large population

e. A beneficial mutation in an extremely small population

e.

When the environment affects the phenotypes of all the genotypes in a population and the reaction norms of the genotypes are parallel,

a. phenotypic variance includes environmental variance, genetic variance, and a genotype by environment interaction.

b. only genetic variance and environmental variation contribute to phenotypic variance.

c. phenotypic variation is driven by genetic variance only.

d. phenotypic variation is driven by environmental variance only.

e. phenotypic variation is driven by a genotype by environment interaction only.

b.

Stabilizing selection is often observed in nature because of

a. selection on variance.

b. trade-offs.

c. linkage disequilibrium.

d. variable selection.

e. realized heritability.

b.

Imagine a population of Galápagos finches that vary for bill size. If the population mean is near the optimum size for eating the seeds found on the island, what would we expect to occur if their main seed resource goes extinct, and another plant with much larger seeds replaces it?

a. Stabilizing selection maintaining the population average

b. Disruptive selection increasing phenotypic variance for bill size

c. Correlational selection between seed size and bill size

d. Directional selection increasing bill size towards a new optimum

e. Extinction of the new plant as finches each all its seeds

d.

Phenotypic variance that is not due to genetic variance can be attributed to

a. environmental variance.

b. dominance.

c. epistasis.

d. pleiotropy.

e. linkage disequilibrium

a.

Which example does not include a case of phenotypic variance?

a. A population of humans in which individuals differ in height

b. A genetically uniform population of barnacles express more muscular reproductive organs in wavy environments

c. A population of bacteria is polymorphic for a single nucleotide polymorphism that resulted from a synonymous mutation

d. A population of garter snakes with several color patterns use different escape behaviors

e. A population of finches has their bill size increased by directional selection

c.

What is meant by the statement "Evolution may proceed along 'genetic lines of least resistance'"?

a. Because mutations may be more likely to appear at some locations in a gene than at others, we can easily predict the phenotype it will experience when natural selection occurs.

b. Evolution operates on the set of phenotypes that a genotype can produce under all possible environmental conditions.

c. Functionally correlated characters will not remain genetically correlated, because they are broken up during segregation and crossing over.

d. Characters with little genetic variation will constrain the rate of natural selection; correlated characters may increase in fitness less rapidly, because they can evolve only along the greatest axis of variation.

e. The phenotypes produced by genes under selection will be those that require the least energy input, despite potential fitness gains.

d.

The phenotypic effect of synergistic interactions among loci is referred to as

a. heritability.

b. dominance.

c. epistasis.

d. pleiotropy.

e. linkage disequilibrium.

c.

Which of the following would likely cause the greatest mean rates of change to morphological characters in a large population with a constant mutation rate?

a. Genetic drift

b. Directional selection

c. Fluctuating selection

d. Stabilizing selection

e. A condition of stasis

b.

Anthropogenic climate change is taking place at such a fast rate that many species will fail to adapt quickly enough to avoid extinction. Which of the following may constrain evolution in response to human-induced climate change?

a. Lack of heritable genetic variation for relevant traits

b. Genetic correlations between relevant traits and other traits that conflict with the direction of selection

c. Loss of genetic variation in relevant traits by genetic drift in dwindling populations

d. Lack of new mutations that allow adaptation to new climate conditions

e. All of the above

e.

Which pair of traits are least likely to be genetically correlated?

a. Two traits that are affected pleiotropically by a single locus

b. Two morphological traits that must "fit" or "work" together

c. A morphological trait that works best with a specific behavioral trait

d. Two traits that are in linkage disequilibrium with each other

e. Two traits whose appearance varies based on the environmental conditions

e.

In correlated selection, selection favors some combination of character states over others, usually because the characters

a. are on different chromosomes.

b. are functionally related.

c. are phenotypically plastic.

d. are canalized.

e. represent a trade-off.

b.

Genetic correlations can have two causes: _______ and _______.

a. linkage disequilibrium; pleiotropy

b. linkage disequilibrium; epistasis

c. epistasis; pleiotropy

d. phenotypic correlation; environmental correlation

e. phenotypic correlation; pleiotropy

b.

Consider a hypothetical locus with several segregating alleles. The population size is small, mutation is absent, and none of the alleles has a selective advantage. Which of the following is likely to occur after a long period of time (many generations)?

a. Allele frequencies will change over time, but all alleles will remain

b. Allele frequencies will cycle over time

c. Genetic variation will decline as alleles randomly go extinct

d. Balancing selection will maintain all the alleles

e. Allele frequencies will remain constant

c.

Which statement about natural selection is true?

a. It is the same as evolution.

b. It always results in reduced genetic variation.

c. It can have an evolutionary effect only if phenotypic differences are heritable.

d. It acts directly on genotypes.

e. Changes in allele frequencies can occur only because of natural selection.

c.

Why did industrial melanism in the peppered moth, Biston betularia, help convince researchers that the intensity of natural selection can be very strong?

a. The dark-colored morph drove the light-colored morph to extinction.

b. Birds were unable to prey on the moths once they acquired their color adaptations.

c. The moth population exploded, covering England with moths during the Industrial Revolution.

d. The dark-colored allele increased in frequency very rapidly in multiple populations and later decreased rapidly after the environment changed.

e. Natural selection maintained constant proportions of the color alleles in the population, despite rapid environmental change brought about by the Industrial Revolution.

d.

Which conditions are required for natural selection to occur?

1. Traits are heritable; offspring resemble parents

2. Traits are coded for by dominant genes

3. Traits are correlated with fitness

4. Populations reproduce sexually

a. 1, 2 and 3

b. 3 and 4

c. 2, 3 and 4

d. 1 and 3

e. All of the conditions

d.

Which of the following is the definition of fitness, according to evolutionary biology?

a. The quality of being able to fulfill a particular role or task

b. The fecundity of a genotype

c. The condition of being physically fit and healthy

d. The viability of a genotype

e. The average, lifetime contribution of individuals with a particular genotype to a population

e.

A change in which variable would not necessarily change an organism's fitness?

a. Mating success

b. Fertilization success

c. Fecundity

d. Mutation rate

e. Viability

d.

A population carries two alleles at a locus. One allele has a miniscule fitness advantage. What is the long-term fate of the locus if natural selection is the only important evolutionary force?

a. Eventually the beneficial allele will be fixed by natural selection.

b. Both alleles will remain in the population at a ratio proportional to the fitness difference.

c. The population size will increase.

d. The population size will decrease.

e. The allele at a disadvantage will mutate to improve to the fitness level of the other allele.

a.

In a scenario where a population is evolving only in response to natural selection, allele frequencies will change at a rate proportional to the selection coefficient and the

a. size of the population.

b. population's growth rate.

c. level of genetic variation at the locus.

d. mean fitness of the population.

e. degree of the allele's penetrance.

c.

What will happen to DNA sequence variation in the regions of the genome immediately adjacent to an allele undergoing a selective sweep, or strong positive selection?

a. Decreased variation and high levels of linkage disequilibrium at nearby sites

b. Increased variation and high levels of linkage disequilibrium at nearby sites

c. Increased variation and the absence of linkage disequilibrium at nearby sites

d. Decreased variation and the absence of linkage disequilibrium at nearby sites

e. No change in local genetic variation

a.

If one genotype in a genetically variable population is favored in dry years and a different genotype is favored in wet years,

a. genetic variation is not necessarily maintained.

b. genetic drift will be a stronger force than selection.

c. genetic variation is always maintained.

d. rates of fixation are likely to speed up.

e. hard selection is likely to occur.

a.

Human sex ratios are close to equal because if one sex becomes rare, it will be at a fitness advantage and increase in frequency in the population until equilibrium at 50:50 is regained. This is an example of

a. overdominance, or heterozygote advantage.

b. negative frequency-dependent selection.

c. positive selection on sex ratio.

d. underdominance, or heterozygote disadvantage

e. positive frequency-dependent selection.

b.

Populations of the grasshopper Vandiemenella viatica possess different chromosomal fusions and inversions. Grasshoppers that are heterozygous for different chromosomal rearrangements have reduced fitness. What would you expect to observe if you investigated the genotypes of grasshoppers in a recently merged population?

a. New combinations of genes yielding genotypes of greater fitness

b. Few heterozygotes because of underdominance

c. Frequency-dependent selection, leading to fluctuations in fitness

d. Heterozygotes with greater fitness, owing to overdominance

e. A random assortment of genotypes because of genetic drift

b.

The end result of positive frequency-dependent selection for a population depends strongly on

a. the sex ratio of the population.

b. the initial frequencies of alleles in the population.

c. the level of background selection.

d. underdominance by heterozygotes.

e. the height of the adaptive peak.

b.

Sewall Wright's metaphor of an "adaptive landscape" that includes "peaks" and "valleys" is used widely in evolutionary biology. Natural selection will always move populations' mean fitness up the peaks. Which influence is most likely to cause a population to move away from a fitness peak towards a valley?

a. Purifying selection

b. Large population size

c. Overdominant selection

d. Positive selection

e. Genetic drift

e.