CH.6-8 Homework Problems

Susan assesses the proportion of plants with pink, blue, or purple flowers. From previous work with the species, the researchers know that flower color is controlled by two genes.

->Susan is collecting data regarding a ________

genetic polymorphism

Larry assesses the variable density of trichomes on the leaves. Trichomes are small, stiff hairs. Their density is influenced by the interaction of multiple genes and environmental factors.

->Larry is collecting data regarding a ________

quantitative trait

Rachel compares the population's dominant life cycle to that of other populations in the region. Seeds that experience a cold autumn season will have a biennial life cycle and produce rosettes that flower their second year. Seeds that experience a warm autumn season will have an annual life cycle and flower the following summer.

->Rachel is collecting data regarding a ________

polyphenism

David assesses the number of seeds that each plant produces. Seed set size depends upon pollinator activity and the number of flowers a plant produces.

->David is collecting data regarding a ________

quantitative trait

Suppose a population of organisms is in Hardy-Weinberg equilibrium. In the population, a gene has two alleles, B and b. If the frequency of B is 0.72 and the frequency of b is 0.28, what are the expected genotype frequencies of BB, Bb, and bb? Calculate each frequency to two decimal places.

BB genotype frequency: ________

Bb genotype frequency: ________

bb genotype frequency: ________

BB genotype frequency: 0.52

Bb genotype frequency: 0.40

bb genotype frequency: 0.08

Which of the following conditions must be met for a population to be in Hardy-Weinberg equilibrium?

infinitely large population

random mating

no mutation

Which example describes random mating as it applies to the Hardy-Weinberg theorem?

A.) Female bullfrogs are more likely to choose the larger and louder male bullfrogs as mates.

B.) For breeding, cattle ranchers use a method of randomization to determine which bull to match with each cow.

C.) A sperm with the albinism allele has equal probability of fertilizing an egg with or without the albinism allele.

D.) A pollen grain carrying the allele for rough leaves is more likely to pollinate an ovule carrying the same allele.

C.) A sperm with the albinism allele has equal probability of fertilizing an egg with or without the albinism allele.

How is the Hardy-Weinberg theorem used as a null hypothesis for evolution?

A.) Scientists apply the theorem as a null hypothesis to estimate the degree of evolution caused by inbreeding of harmful alleles within a population.

B.) Scientists use the theorem as a null hypothesis for evolution because the theorem describes the conditions under which allele frequencies do not change.

C.) Scientists accept the null hypothesis when the predicted and observed allele frequencies are statistically different and evolution has occurred.

D.) Scientists use the theorem as a null hypothesis to determine if evolution by natural selection will drive an allele to fixation or extinction.

B.) Scientists use the theorem as a null hypothesis for evolution because the theorem describes the conditions under which allele frequencies do not change.

How is genetic drift related to population size?

A.) Genetic drift affects a small population more drastically than a large population.

B.)The larger the population size, the greater the effect of genetic drift.

C.) No relationship exists between population size and genetic drift.

D.) Genetic drift occurs more often in a large population than in a small population.

A.) Genetic drift affects a small population more drastically than a large population.

Determine if each described population is experiencing Hardy-Weinberg equilibrium, selection, or genetic drift.

Suppose that of a population of 1000 dolphins, only 64 individuals produce the next generation of offspring. By chance, the reproducing individuals carry allele d at a frequency of 0.24, whereas the frequency of the allele in the population is 0.76. After the birth of the new generation, the allele frequency for d is 0.60 in the population.

genetic drift

Determine if each described population is experiencing Hardy-Weinberg equilibrium, selection, or genetic drift.

Suppose that geneticists are tracking a gene in a mouse population and measuring the frequencies of the gene's two alleles, B and b, over time. In the initial population, the allele frequencies for B and b were 0.845 and 0.155, respectively. Forty generations later, the frequencies of alleles B and b are not statistically different than any previous measurements.

equilibrium

Determine if each described population is experiencing Hardy-Weinberg equilibrium, selection, or genetic drift.

Suppose that a frog population includes individuals with either a short or long tongue. Sixty‑five percent of the frogs have a long tongue and are more successful at catching insect prey. The long‑tongued frogs have greater fitness than the short‑tongued frogs. After several generations, 82% of the frog population has a long tongue.

selection

Suppose a population of organisms is in Hardy-Weinberg equilibrium with respect to a gene that has two alleles, Y and y. The YY genotype has a frequency of 0.11, the Yy genotype has a frequency of 0.44, and the yy genotype has a frequency of 0.45. Calculate the frequency of each allele to two decimal places.

Y allele frequency: ________

y allele frequency: ________

Y allele frequency: 0.33

y allele frequency: 0.67

Genetic drift can be caused by a variety of events. A genetic bottleneck, which is one such event, results when ________. Genetic drift due to the founder effect results when ________. Populations resulting from either a genetic bottleneck or the founder effect tend to have ________ allele variations than the original population. The effects of genetic drift last for many generations.

a population loses most of its members; a small group is permanently isolated from a larger population; fewer

One way scientists study evolution within populations is by measuring allele frequencies at specific genetic loci. Scientists calculate allele frequencies within populations, then observe how allele frequencies change over time.

This field of study is called ________

population genetics

Imagine that a peacock hatches with a mutation in a gene involved with tail feather growth. The mutation produces an allele dominant to the original allele. The new dominant allele makes the tail display more attractive to peahens than the recessive allele.

What effect is natural selection likely to have on the frequencies of the two alleles over the next several generations?

A.) The dominant allele will be fixed, and the population will lose the recessive allele because females prefer the males that have the dominant allele.

B.) The dominant allele will increase in frequency, but the recessive allele will remain because heterozygous males are as attractive as homozygous dominant males.

C.) The single dominant allele in the population may be lost after the first generation because the male with the allele may not pass it on to any of his offspring.

D.) The frequencies of the two alleles will be nearly equal once the

B.) The dominant allele will increase in frequency, but the recessive allele will remain because heterozygous males are as attractive as homozygous dominant males.

For each situation, predict whether the allele frequency is likely to increase or decrease in the population due to natural selection.

A dominant allele is beneficial to individuals that carry it.

the allele frequency will increase rapidly, but the allele will not become fixed

For each situation, predict whether the allele frequency is likely to increase or decrease in the population due to natural selection.

A dominant allele is deleterious to individuals that carry it.

the allele frequency will decrease until the allele is lost from the population

For each situation, predict whether the allele frequency is likely to increase or decrease in the population due to natural selection.

A recessive allele in a population with some homozygous recessive individuals is beneficial to individuals carrying the allele.

the allele frequency will increase steadily until the allele becomes fixed

For each situation, predict whether the allele frequency is likely to increase or decrease in the population due to natural selection.

A recessive allele in a population with some homozygous recessive individuals is deleterious to individuals carrying the allele.

the allele frequency will decrease, but the allele will remain in the population

For each situation, predict whether the allele frequency is likely to increase or decrease in the population due to natural selection.

An additive allele is beneficial to individuals that carry it.

the allele frequency will increase steadily until the allele becomes fixed

For each situation, predict whether the allele frequency is likely to increase or decrease in the population due to natural selection.

An additive allele is deleterious to individuals that carry it.

the allele frequency will decrease until the allele is lost

An allele's ________ determines the probability that genetic drift will result in the allele's fixation. The higher the allele's frequency, the ________ that the allele will become fixed in the population. In addition, as one allele goes to fixation, the heterozygosity of the population ________.

The rate at which heterozygosity changes with genetic drift depends on the ________ and the ________.

starting frequency; higher the probability; decreases; original heterozygosity; size of the population

Gregor Mendel studied a variety of visible traits in garden peas, including pea color, flower color, and shape of the pea's pod. Mendel found that pea pods could be inflated or constricted and that this trait was controlled by two alleles, I and C, respectively, at a single gene.

Suppose Mendel had 452452 pea pods and knew that there were 692692 I alleles and 212212 C alleles in these pods.

Calculate the probability of fixation for each allele. Express the probabilities to two decimals. Assume that no evolutionary forces other than genetic drift act on pea pod shape.

-probability of fixation of I: _________

-probability of fixation of C: ________

-Which allele is more likely to go to fixation?

-Which allele is more likely to be lost from the population?

-probability of fixation of I: 0.77

-probability of fixation of C: 0.23

-the I allele

-the C allele

Suppose that a modern geneticist grows the same variety of garden peas that Gregor Mendel did. She randomly selects a single pea from 10 plants in her test garden and quantifies the alleles at a single locus. The frequency of heterozygotes in this first generation of 10 peas equals 0.70. She plants these peas and then selects 10 more peas from this population. She repeats this process two more times so that she has the original population, generation 1, and three successive generations of plants, generations 2, 3, and 4.

Using Wright's equation, predict the frequency of heterozygotes in generations 2, 3, and 4. Assume that the only evolutionary mechanism affecting heterozygosity is genetic drift. Express each frequency to two decimal places.

-frequency of heterozygotes in generation 2: ________

-frequency of heterozygotes in generation 3: ________

-frequency of heterozygotes in generation 4: ________

-frequency of heterozygotes in generation 2: 0.67

-frequency of heterozygotes in generation 3: 0.64

-frequency of heterozygotes in generation 4: 0.61

Humans first released the Japanese bush‐warbler on the Hawaiian island of Oahu in the early twentieth century. Since that time, the warblers have colonized most of the Hawaiian Islands. The birds colonized Kauai, Molokai, and Maui around 1980 and the big island of Hawaii in 1997.

In a 2018 study, scientists studied the genetic structure of populations of bush‐warblers located on each Hawaiian island. The researchers measured heterozygosity on each of the larger Hawaiian Islands. For three of these islands, Oahu, Kauai, and the big island of Hawaii, the heterozygosity was 0.52, 0.49, and 0.46, respectively.

Suppose that scientists had also estimated bush‐warbler population size on each island and that Oahu had 25 birds, Kauai had 25 birds, and Hawaii had only 55 birds.

Use Wright's equation to calculate the frequency of the heterozygotes in the next generation on each of the three islands. Express the predicted hetero

-frequency of heterozygotes on Oahu: 0.52

-frequency of heterozygotes on Kauai: 0.48

-frequency of heterozygotes on Hawaii: 0.41

1. On Oahu, the loss of heterozygosity due to genetic drift will likely be very slow, whereas the loss on Hawaii is likely to be much faster.

2. Wright's equation predicts that the rate of loss of heterozygosity on Kauai should be intermediate to the other islands.

Suppose that you are studying genetics in a population of organisms. You have values for the number of individuals in each of three genotypes and want to know if the genotypes are in Hardy-Weinberg equilibrium. To do this, you need to calculate a X2X2 value from the number of individuals in each genotype in the population.

Place the calculations you would use to determine if the population is in Hardy-Weinberg equilibrium. The last step in which the X2X2 value is compared to a statistical table has already been added to the list of steps.

[Observed number of individuals in each genotype]

calculate the observed genotype frequencies -> calculate the observed allele frequencies -> calculate the expected genotype frequencies -> calculate the expected number the individuals in each genotype -> calculate the X^2 value [Compare the X^2 value in a statistical table of X^2 values]

The HMGA2 gene is strongly correlated with height in humans. One allele of the gene, T, codes for tall humans, whereas another allele, S, codes for shorter humans. The effect of the T allele is additive. That is, one copy of the T allele results in a slightly taller person, whereas two copies of the allele result in a very tall person.

Suppose that a population of individuals contains 628 short individuals with the SS genotype, 245 medium height individuals with the TS genotype, and 127 very tall individuals with the TT.

Calculate the frequencies of each genotype. Express each frequency to three decimal places.

-SS genotype frequency: ________

-TS genotype frequency: ________

-TT genotype frequency: ________

Calculate the frequencies of the T and S alleles in this population. Express the frequencies to two decimal places.

-S allele frequency: ________

-T allele frequency: ________

-SS genotype frequency: 0.63

-TS genotype frequency: 0.25

-TT genotype frequency: 0.13

-S allele frequency: 0.76

-T allele frequency: 0.25

Geneticists have investigated many of the genes that control the length, color, and texture of fur in domesticated dogs. One gene, RSPO2, controls the texture of a dog's coat and whether or not the dog has a long mustache and eyebrows. An allele at this gene, W, has incomplete dominance and codes for a wiry coat and a long mustache and eyebrows. The other gene, w, codes for a soft coat, no mustache, and short eyebrows. The three genotypes of these alleles have unique phenotypes. Dogs with the WW genotype have very coarse hair and long mustaches and eyelashes. Dogs with the Ww genotype have slightly wiry hair and shorter mustaches and eyebrows. Dogs with the ww genotype have soft hair, no mustache, and short eyebrows.

Suppose that there are 393 dogs in a population. The frequency of the W allele in the population is 0.63, and the frequency of the w allele is 0.37.

Calculate the expected frequency of each genotype fr

-expected genotype frequency of WW: 0.40

-expected genotype frequency of Ww: 0.47

-expected genotype frequency of ww: 0.139

-expected number of dogs with the WW genotype: 155.98

-expected number of dogs with the Ww genotype: 183.22

-expected number of dogs with the ww genotype: 53.80

Genetic drift results in the ________ in

allele frequency from generation to generation, whereas natural selection results in a ________ in

allele frequency. In large populations, ________ drives allele frequencies to fixation or loss with little influence from ________. In contrast, ________ swamps the effect of ________

in small populations.

random change; directional change; natural selection; genetic drift; genetic drift; natural selection

In each of these scenarios, determine whether genetic drift or natural selection should dominate evolution.

The Javan rhino once roamed the forested habitats from India and China to Southeast Asia. Loss of habitat and poaching have reduced the number of Javan rhinos to fewer than 60 individuals, which exist in an isolated population in Indonesia.

dominated by genetic drift

In each of these scenarios, determine whether genetic drift or natural selection should dominate evolution.

Wildebeest live on the Serengeti and can migrate in herds of up to 1.5 million individuals. Selection pressures include predation by lions and extremely dry periods when both food and water are limited.

dominated by natural selection

In each of these scenarios, determine whether genetic drift or natural selection should dominate evolution.

Quaking aspen ranges across the North American continent from Alaska to Newfoundland and as far south as Mexico. Aspens do not form one continuous population but often exist in large populations of thousands of individuals. Selection pressures include drought and insect herbivory.

dominated by natural selection

In each of these scenarios, determine whether genetic drift or natural selection should dominate evolution.

Yellow-bellied marmots live high atop mountains in the western United States. Inhospitable conditions found between mountaintops separate marmot populations. The southernmost populations of marmots exist in small areas with few individuals. Predation and harsh winter conditions impose selection pressure on marmots.

dominated by genetic drift

African elephants once existed in large populations across the African continent. Elephants use their tusks to dig for water and food. Humans hunt and kill elephants for their tusks. Habitat loss and fragmentation have also reduced the total number of elephants and the size of elephant herds. Scientists estimate that the number of African elephants has decreased from several million to several hundred thousand. Population sizes range from over 100,000 individuals in Botswana to approximately 100 individuals in northern Cameroon. Scientists have also found that the frequency of elephants that never develop tusks is increasing.

Select all the statements that describe probable effects of poaching and habitat fragmentation on elephant evolution.

-The elephant population in Cameroon will experience high levels of genetic drift.

-The poaching of elephants for their tusks is leading to the evolution of tuskless elephants.

-Habitat fragmentation leads to decreases in population size and increases in genetic drift.

Geographic barriers split populations into smaller populations, each of which will continue to evolve. In each of the scenarios, predict the genetic consequences of the division of a population of organisms.

Suppose a four‐lane highway is built through a population of frogs, dividing the population into two subpopulations. After a heavy rain, some frogs are able to cross the road and mate with frogs from the other population.

A.) Complete genetic isolation will result in an increase in genetic distance between the subpopulations.

B.) Because of the continued gene flow, the subpopulations will maintain some genetic similarity.

C.) The two smaller populations will be less affected by genetic drift than the large population.

D.) Because selection pressures are the same, the populations will evolve in similar ways.

B.) Because of the continued gene flow, the subpopulations will maintain some genetic similarity.

Geographic barriers split populations into smaller populations, each of which will continue to evolve. In each of the scenarios, predict the genetic consequences of the division of a population of organisms.

Pika are small mammals that live above treeline on alpine tundra. As the climate warms, treeline moves to higher altitudes, forcing pika populations into smaller areas on the tops of mountains. These small areas support only a limited number of pika. In addition, pika do not migrate through forested areas, causing populations to become increasingly isolated from one another.

A.) Smaller habitat size will lead to fewer territorial disputes and higher fitness levels.

B.) Shrinking pika population size will result in a decrease in the amount of genetic drift.

C.) As pika population size decreases, inbreeding and inbreeding depression will increase.

D.) Gene flow among populations will result in a decrease in the pr

C.) As pika population size decreases, inbreeding and inbreeding depression will increase.

Geographic barriers split populations into smaller populations, each of which will continue to evolve. In each of the scenarios, predict the genetic consequences of the division of a population of organisms.

When the Great Rift Valley opened in eastern Africa, very large lakes formed in the valley. The lakes divided the populations of many terrestrial plant species. Suppose that plant populations on the western side of the lakes evolve independently of populations on the eastern side of lakes.

A.) If selection pressures vary between the populations, genetic distance will decrease.

B.) Differences in selection pressures between the populations will increase the effect of genetic drift.

C.) Eastern and western populations of plants will become genetically distinct through genetic drift.

D.) The larger the eastern and western populations are, the more rapidly they will be isolated by genetic drift.

C.) Eastern and western populations of plants will become genetically distinct through genetic drift.

Repeated inbreeding results in the loss of ________ a population. In addition, more individuals in the population are likely to be homozygous for deleterious, recessive alleles, resulting in ________ individual and population fitness.

genetic diversity from; low

Genetic drift can be caused by a variety of events. A genetic bottleneck, which is one such event, results when ________.

Genetic drift due to the founder effect results when ________. Populations resulting from either a genetic bottleneck or the founder effect tend to have ________ allele variations than the original population. The effects of genetic drift last for many generations.

a population loses most of its members; a small group is permanently isolated from a larger population; fewer

Suppose scientists studied a species of plant that grows in shady environments. They measured the size of leaves in two plant populations and found that the size distribution was similar. In addition, they found that plants with larger leaves tended to produce more seeds and that their offspring tended to have large leaves.

The scientists also measured the selection differential, S, of leaf size in each population. In population A, S equalled 1 cm^2. In population B, S equalled 2 cm^2.

Assume that the heritability of leaf size in the two populations is the same. Predict how the difference in S between the populations will affect the evolution of leaf size in these populations.

-Because S is larger in population B, leaf size will evolve more rapidly in population B than in A.

-After a given number of generations, the leaves in population B will be larger than those in A.

In which of these scenarios would quantitative trait locus (QTL) analysis be useful?

-to examine the cumulative effects of childhood diet on final adult height of humans

-to locate all the genes that influence the mating dances of birds of paradise

-to determine how many chromosomes influence seed weight in the plant Arabidopsis thaliana

-to identify which genes increase the risk of cardiovascular disease in humans

-to explain the interaction between the sickle cell anemia allele and the normal hemoglobin allele

-to locate all the genes that influence the mating dances of birds of paradise

-to determine how many chromosomes influence seed weight in the plant Arabidopsis thaliana

-to identify which genes increase the risk of cardiovascular disease in humans

Quantitative trait locus (QTL) analysis links the ________ of a quantitative trait to ________, called loci. For QTL analysis, scientists correlate phenotypic variation with genetic variation by using ________. Loci that are statistically correlated with the trait of interest usually indicate that ________ contribute to phenotypic variation in the trait.

phenotypic variation; genetic regions of interest; genetic markers; nearby genes

Each summer, farmers compete to grow the largest pumpkin, which can weigh thousands of pounds. They go to great lengths to help their pumpkin grow, including using extra fertilizer, heaters on cool spring days, and enclosures to reduce herbivory by insects.

Suppose that botanists measure the variation in pumpkin weight due to genetic composition and environmental factors. They measure variation in standard deviations. Variation due to genetic composition equals 254 pounds, whereas the variation due to environmental factors equals 385 pounds.

From these data, calculate the phenotypic variance in pumpkin weight.

phenotypic variance: ________

639

Determine whether each scenario is an example of phenotypic plasticity or evolution in a phenotype's plasticity.

The leaves growing in shade on a sugar maple tree are larger than the leaves growing in full sun on the same tree.

phenotypic plasticity

Determine whether each scenario is an example of phenotypic plasticity or evolution in a phenotype's plasticity.

The skin of a green anole lizard shifts from green to brown when the anole moves from a leaf to the bark of a tree.

phenotypic plasticity

Determine whether each scenario is an example of phenotypic plasticity or evolution in a phenotype's plasticity.

The fur of snowshoe hares is brown in summer and white in winter, but populations in warming areas have begun to retain their brown fur.

evolution in a phenotype's plasticity

Which studies could be conducted using genome‑wide association mapping?

-Researchers compare the genomes of 5000 leukemia patients to the genomes of 5000 people without leukemia to identify genes associated with this type of cancer.

-Scientists identify genes controlling stamen length in Arabidopsis thaliana by comparing the genomes of 6000 short‑stamen plants to an equal number of long‑stamen plants.

-Biologists searching for genes governing petal color in coneflowers examine the second generation offspring of a cross between purple and white coneflowers.

-Geneticists study the F2 progeny of a cross between two populations of zebra finches with different body sizes to determine the locations of genes possibly involved with body size.

-Researchers compare the genomes of 5000 leukemia patients to the genomes of 5000 people without leukemia to identify genes associated with this type of cancer.

-Scientists identify genes controlling stamen length in Arabidopsis thaliana by comparing the genomes of 6000 short‑stamen plants to an equal number of long‑stamen plants.

Why do calculations for narrow sense heritability not include dominance or epistasis?

A.)The effects of dominance and epistasis increase during meiosis and exaggerate trait expression.

B.) Dominance and epistasis are primarily responsible for offspring resembling their parents.

C.) The effects of dominance and epistasis depend on the presence of other inherited alleles.

D.) Dominance and epistasis are additive and do not depend on interactions with other alleles.

C.) The effects of dominance and epistasis depend on the presence of other inherited alleles.

________ genetics is the study of evolutionary mechanisms of continuous variation in phenotypic traits.

Continuous, or quantitative, traits are frequently ________ traits that depend on alleles at multiple loci. Additive effects of alleles or nonadditive interactions among alleles, also known as ________,

may influence trait expression. Also, the ________ of alleles in response to the environment may affect the degree of their expression.

quantitative; polygenic; epistasis; plasticity

Select the statements that describe broad‐sense heritability.

-the greater the influence of genetic factors, the smaller the value of broad‑sense heritability

-the total phenotypic variation in a trait, which includes genetic and environmental factors

-a measure of the relative importance of genetic factors to the phenotypic variation of a trait

-the portion of phenotypic variation not associated with environmental factors

-the portion of phenotypic variation associated with additive alleles

-a measure of the relative importance of genetic factors to the phenotypic variation of a trait

-the portion of phenotypic variation not associated with environmental factors

Suppose that an ornithologist measured tail length in a population of black‐capped chickadees, a type of small bird found in the northern United States and Canada. Variation in tail length due to genetic differences, environmental differences, and the interaction of genetic and environmental factors equaled 47, 27, and 14, respectively.

Calculate the total variation, 𝑉𝑃, in tail length for this population of chickadees.

𝑉𝑃: ________

88

Many wildflowers depend on pollinators, such as bees, moths, and hummingbirds, for the successful production of seeds. Penstemons have flowers that are well‐suited to pollination by bumblebees. Their flowers provide a sugary nectar for the bees and are the right size and shape for a bumblebee's body.

Suppose that scientists measured flower length and the concentration of sugar in nectar. They found that the variation in flower length was 25 and the variation in sugar concentration was 121. The genetic component of variation, 𝑉𝐺, for flower length was 23.5, and for sugar concentration, 45.

Calculate the broad‐sense heritability, 𝐻^2, for flower length and sugar concentration. Express 𝐻^2 to two decimal places.

-𝐻^2 of flower length: ________

-𝐻^2 of sugar concentration: ________

What conclusion can you draw from these results?

-𝐻^2 of flower length: 0.94

-𝐻^2 of sugar concentration: 0.37

A.) Offspring should have sugar concentrations that are similar to their parents.

B.) Flower length is more influenced by genetic factors than sugar concentration is.

The Lifeline Cohort Study examines the effects of genetic factors and environmental conditions on a wide variety of human health biomarkers in nearly 170,000 Scandinavians. Measures include body mass index (BMI), total cholesterol, fasting glucose, and approximately 30 other traits.

Suppose researchers calculated each of the components of phenotypic variation for BMI. They found that the genetic component of variation equals 2.46, the environmental component of variation equals 5.44, and the variation associated with interaction of genetic and environmental factors to be 1.21.

Calculate the broad‐sense heritability, 𝐻^2, for BMI. Express 𝐻^2 to two decimal places.

𝐻^2 of BMI: ________

0.27

Select the statements that describe narrow‐sense heritability, h^2.

-calculated by dividing the additive component of genetic variation by phenotypic variation

-calculated using the y‐intercept of a parent:offspring regression line

-includes the components of variation associated with epistasis and dominance

-quantifies only a portion of the genetic component of phenotypic variation

-quantifies the most predictable component of heritability

-calculated by dividing the additive component of genetic variation by phenotypic variation

-quantifies only a portion of the genetic component of phenotypic variation

-quantifies the most predictable component of heritability

Children's faces often resemble their parents' faces, which suggests that facial features are heritable. Scientists recently investigated the components of phenotypic variation of facial features in humans.

Suppose that the scientists measured each component of phenotypic variation for nose width. The variation associated with additive alleles was 86., with dominant alleles was 11.6, with epistatic interactions was 2.7, with environmental factors was 19.3, and with the interaction of genetic and environmental factors was 0.5.

Calculate the amount of phenotypic variation associated with genetic factors, VG. Express VG to one decimal place.

VG: ________

Which of these variables could also be calculated with the values given?

VG: 101.2

-broad‐sense heritability, H^2

-total phenotypic variation, VP

Complete each of the sentences about the Breeder's equation.

The Breeder's equation states that the response to selection, R, is a function of the selection differential, S, and ________. As the selection differential becomes larger, R becomes ________. In addition, if heritability is ________, then regardless of how large S is, there will be ________.

narrow-sense heritability, h^2; larger; 0; no response to selection

Suppose that a scientist studies how selection affects the foraging distance of mice. She begins her experiment with a population of mice with a mean foraging distance of 3.5 meters. She selects mice from the population that forage the greatest distance to produce a second generation of mice. The mice selected to produce the second generation have a mean foraging distance of 5.8 meters. The resulting offspring have a mean foraging distance of 4.3 meters.

Calculate the selection differential, S, for foraging distance. Express S to one decimal place.

S: ________ meters

Calculate the response to selection, R, for foraging distance. Express R to one decimal place.

R: ________ meters

2.3 meters

0.8 meters

Suppose that a botanist is studying grain yield in rice and wants to increase yield through selective breeding. His rice currently yields 3.2 tons per hectare. The botanist selects the highest‐yielding plants from the population to produce a second generation of plants. The breeding population has a yield of 6.1 tons per hectare. When the botanist grows the seed produced by the breeding population, he finds that the second generation of plants has a yield of 4.9 tons per hectare.

From these data, calculate the narrow‐sense heritability, h^2, of grain yield in this strain of rice. Express h^2 to two decimal places.

h^2: ________

0.59

Suppose a biologist measured the end of hibernation in wood frogs in southern Canada. The mean day that the frogs emerged from hibernation was on day 103 of the year, which corresponds to April 13. A cohort of frogs was able to emerge on a mean date of March 28, or day 87 of the year. In addition, the biologist measured the narrow‐sense heritability, h^2, of emergence, which equaled 0.27. Assume that the frogs that emerged from hibernation early produced most of the progeny for the year.

From these data, calculate the response to selection, R, for the end date of hibernation. Express R to one decimal place.

R: ________ days

-4.32

Poodle breeders have selectively bred poodles in three sizes. Standard poodles are about 22 inches at the shoulder, miniature poodles are approximately 14 inches, and toy poodles are less than 10 inches.

Suppose that you begin with a miniature poodle and want to breed a new type of toy poodle. The original population of miniature poodles has a mean height of 14 inches, but the dogs chosen to produce the next generation of poodles has a mean height of only 12 inches. The next generation of dogs has a mean height of 12.4 inches.

Calculate the selection differential, S, for poodle size. Express S to one decimal place.

S: ________

Calculate the response to selection, R, for poodle size. Express R to one decimal place.

R: ________

Calculate the narrow‐sense heritability, h^2, for poodle size. Express h^2 to two decimal places.

h^2: ________

Assuming that S, R, and h2 remain constant, determine the minimum number of ge

S: -2.0

R: -1.6

h^2: 0.8

3

Sort the characteristics of maximum likelihood and Bayesian methods of analysis.

-determines the probability that a data set can be reconstructed

maximum likelihood methods

Sort the characteristics of maximum likelihood and Bayesian methods of analysis.

used to evaluate phylogenies

both maximum likelihood and bayesian methods

Sort the characteristics of maximum likelihood and Bayesian methods of analysis.

determines the probability that a hypothetical tree is correct

bayesian methods

Sort the characteristics of maximum likelihood and Bayesian methods of analysis.

analysis begins with an a prori evolutionary model

both maximum likelihood and bayesian methods

Methods of ________ build phylogenies with the assumption that evolution occurs in the most straightforward way. One method of reconstructing evolutionary history is to examine ________ in protein‑coding genes. Due to selection for functionality, ________ selection eliminates deleterious mutations, causing protein-coding genes to evolve slowly and conserve signatures of relatedness. Another method, called ________, is when scientists build thousands of theoretical phylogenies with random characters from the data set and compare them to each other. Parts of the trees that are ________ similar carry more support for presenting the correct evolutionary hypothesis.

maximum parsimony; exons; purifying; bootstrapping; most

Predict how each situation would affect how quickly coalescence occurred.

A beneficial allele experiences positive selection.

coalescence happens rapidly, occurring closer to the tips of the gene tree

Predict how each situation would affect how quickly coalescence occurred.

A neutral allele exists in a small population.

coalescence happens rapidly, occurring closer to the tips of the gene tree

Predict how each situation would affect how quickly coalescence occurred.

A neutral allele exists in a large population

coalescence happens slowly, taking many generations

Predict how each situation would affect how quickly coalescence occurred.

Two alleles exist that both have some positive and some negative effects.

coalescence happens slowly, taking many generations

What is the most likely explanation for all extant copies of a gene coalescing?

A.) All the extant copies of the gene were inherited from the single ancestor in which the allele originated.

B.) One gene copy out of the multitude of copies that existed in the past gave rise to all the extant copies.

C.) A neutral allele that has persisted longer than any other is the ancestor of all the extant gene copies.

D.) Each extant copy of the gene bears the same mutation which occurred in multiple different ancestors.

B.) One gene copy out of the multitude of copies that existed in the past gave rise to all the extant copies.

For which purposes can scientists use molecular phylogenies?

1. to eliminate diseases from infected populations

2. to trace the origin of pathogens among populations

3. to identify adaptations for infection or transmission

4. to predict the evolution and emergence of new diseases

2. to trace the origin of pathogens among populations

3. to identify adaptations for infection or transmission

4. to predict the evolution and emergence of new diseases

How is the neutral theory of evolution used to deduce the timing of evolutionary events and the history of natural selection?

A.) Scientists observe the number of gene duplications to date events and apply the theory to determine the amount of change attributable to selection.

B.) Scientists date events knowing that neutral mutations are fixed in a population through drift much faster than they are through selection.

C.) Scientists apply the idea that the further back in time a branching event occurred, the fewer fixed neutral mutations a lineage carries.

D.) Scientists use a steady rate of mutation accumulation to date events and apply the theory as a null hypothesis for natural selection.

D.) Scientists use a steady rate of mutation accumulation to date events and apply the theory as a null hypothesis for natural selection.

How are gene trees used to describe the history of a gene?

A.) Gene trees depict the most ancient genealogy of a gene using sampling from a single population.

B.) Gene trees show a hypothesis about a gene's lineage using nucleotide sequences and mutation rates.

C.) Gene trees indicate the path of descent of an allele by denoting its expression in a morphological feature.

D.) Gene trees show evolutionary relationships among the alleles of a gene within and between populations.

D.) Gene trees show evolutionary relationships among the alleles of a gene within and between populations.

Select statements that describe molecular clocks.

1. Different segments of DNA acquire mutations at different rates.

2. Fossils can allow scientists to calibrate mutation rates.

3. Mutations increase fitness and the likelihood of fixation.

4. Base‑pair substitutions occur at a predictable rate.

1. Different segments of DNA acquire mutations at different rates.

2. Fossils can allow scientists to calibrate mutation rates.

4. Base‑pair substitutions occur at a predictable rate.

Sort the scenarios according to whether the mutations would spread by natural selection, neutral evolution, or both.

a mutation in a protein-coding gene changes the amino acid sequence of a protein

natural selection

Sort the scenarios according to whether the mutations would spread by natural selection, neutral evolution, or both.

a mutation in a pseudogene produces no downstream consequences

neutral evolution

Sort the scenarios according to whether the mutations would spread by natural selection, neutral evolution, or both.

a mutation in a protein-coding gene becomes fixed in a population

both natural selection and neutral evolution

Sort the scenarios according to whether the mutations would spread by natural selection, neutral evolution, or both.

a mutation in a protein-coding gene does not change the amino acid sequence of a protein

neutral evoultion

Sort the scenarios according to whether the mutations would spread by natural selection, neutral evolution, or both.

a mutation in a pseudogene changes the transcription rate of a protein

natural selection

Evolutionary biologists use morphological characters to create species trees. Similarly, scientists use ________ characters to create gene trees. More specifically, the characters of a gene tree are the ________ of a gene's nucleotide sequence.

When a ________ event occurs, a new allele arises in the gene tree. This divergence is represented by a ________, and each of the various alleles in the sample group are represented by a ________, with one common ancestral allele at the ________.

molecular; bases

mutation; branch; tip; root

A constructed gene history does not always reflect the history of the species in which the gene is embedded. With ________, different alleles pass into newly isolated populations by chance and may be randomly lost over time. Discrepancy between gene and species trees also occurs with ________, or the introduction of new genes into a species through hybridization.

incomplete lineage sorting; introgression

Suppose that scientists are investigating populations of a species of phlox to determine if the they are evolving different adaptations to their local environments. They investigate multiple segments of DNA to identify locations of synonymous (𝑑/S) and non‑synonymous (𝑑/N) mutations. For each scenario, determine whether scientists should accept or reject the null hypothesis of neutral evolution.

The light environment for each population differs. The scientists analyze a gene related to stem structure and find that the frequency of non‑synonymous mutations is much less than the frequency of synonymous mutations.

reject the null hypothesis of neutral evolution

Suppose that scientists are investigating populations of a species of phlox to determine if the they are evolving different adaptations to their local environments. They investigate multiple segments of DNA to identify locations of synonymous (𝑑/S) and non‑synonymous (𝑑/N) mutations. For each scenario, determine whether scientists should accept or reject the null hypothesis of neutral evolution.

Each population has a different frequency of asters with blue or purple flower petals. Scientists investigate a gene for petal color and find that the frequency of non‑synonymous mutations is nearly the same as the frequency of synonymous mutations.

accept the null hypothesis of neutral evolution

Suppose that scientists are investigating populations of a species of phlox to determine if the they are evolving different adaptations to their local environments. They investigate multiple segments of DNA to identify locations of synonymous (𝑑/S) and non‑synonymous (𝑑/N) mutations. For each scenario, determine whether scientists should accept or reject the null hypothesis of neutral evolution.

-The populations are in fields with different hydrology. The scientists analyze a gene related to root structure and determine that the frequency of non‑synonymous mutations is much greater than the frequency of synonymous mutations.

-The data suggest that which traits are under selection?

-reject the null hypothesis of neutral evolution

-stem structure and root structure