Chapter 19 Quiz

Explain why small populations are more vulnerable to the forces of genetic drift than large populations. a) The more individuals in a population, the larger and more stable is its gene pool. b) The more individuals in a population, the more alleles are present in its gene pool. c) The fewer individuals in a population, the more likely it is to go extinct. d) The fewer individuals in a population, the more room there is for new individuals to migrate into it.

a) The more individuals in a population, the larger and more stable is its gene pool.

What is fitness the measure of? a) successful reproduction b) the effect of chance on a population's gene pool c) the abnormalities in a population d) the frequency of beneficial alleles

a) successful reproduction

Heterozygote advantage is a condition in which heterozygotes are favored by natural selection. How would the value of 2pq likely change if the population was undergoing heterozygote advantage? a) It would not remain in equilibrium because the value of 2pq would likely increase. b) It would remain in equilibrium because the value of p and q would remain the same. c) It would remain in equilibrium because the value of 2pq would remain the same. d) It would not remain in equilibrium because the value of 2pq would likely decrease.

a) It would not remain in equilibrium because the value of 2pq would likely increase.

Antibiotics are medicines that are designed to kill disease-causing organisms, or pathogens. However, some pathogens evolve antibiotic resistance, where they gain traits that allow them to survive in the presence of antibiotics. The ability of bacteria to adapt to antibiotics so quickly has created a huge concern over whether antibiotics are being overused. What form of evolution is antibiotic resistance an example of, and why? a) Natural selection, because the bacteria is adapting to a new environmental condition - the presence of the antibiotic. b) Mutation, because each bacteria must mutate to an antibody resistant form in order to survive. c) Genetic drift because medical workers cannot follow the randomly-fluctuating gene frequencies of bacterial populations d) Gene flow because the bacteria are passing on the resistant trait within their populations.

a) Natural selection, because the bacteria is adapting to a new environmental condition - the presence of the antibiotic.

Explain the founder effect and identify the best example. a) The founder effect is an event that isolates part of a population, generating an allele frequency which is not typical of the original population. An example of the founder effect is the Amish population. The Amish population was established from about 200 German immigrants. Individuals of this founding population carried gene mutations that cause inherited disorders such as Ellis-van Creveld syndrome. This form of dwarfism is found in a large concentration in the Amish population today because the immigrants that established the population had a high concentration of the disorder in a very small population. b) The founder effect is when only a few males within a population are selected by females to reproduce, generating an allele frequency which is different from the original population. An example of the founder effect is the reproductive pattern of mountain gorillas. Mountain gorillas tend to have a single dominant male, the silverback, who gets the vast majority of the matings in the population. This leads to the next generation expressing mainly genes from the silverback and very few genes from the other males, changing the genetic structure of the population. c) The founder effect is an event that kills off a significant proportion of a population, generating an allele frequency which is not typical of the original population. An example of the founder effect is the Northern elephant seal. At one point, hunting of these seals had reduced their numbers to less than 50 individuals. The population has since rebounded, but still contains less genetic variation than the related Southern elephant seal due to the loss of some alleles. d) The founder effect occurs when the selective pressure on a trait varies depending on the alleles expressed within the population, generating varying allele frequencies based on the genetic makeup of the original population. An example of the founder effect is the cyclical dominance of three throat-color patterns in side-blotched lizards.

a) The founder effect is an event that isolates part of a population, generating an allele frequency which is not typical of the original population. An example of the founder effect is the Amish population. The Amish population was established from about 200 German immigrants. Individuals of this founding population carried gene mutations that cause inherited disorders such as Ellis-van Creveld syndrome. This form of dwarfism is found in a large concentration in the Amish population today because the immigrants that established the population had a high concentration of the disorder in a very small population.

In the past, it is thought that wolves used to be attracted to human settlements, where they could scavenge for food remains. At some point, humans may have attempted to feed the wolves. The more docile members of the pack may have accepted this food, and maintained a close association with humans, as the humans offered them food and safety. However, the more ferocious members of the pack would be driven away and would not receive any of these benefits. How would the wolves that were allowed to live with humans evolve and what form of evolution is this an example of? a) The wolves living with humans will likely continue to be selected by humans to be more tame and docile. This is an example of artificial selection. b) The wolves living with humans will likely start to be selected by humans to be more ferocious. This is an example of natural selection. c) The wolves living with humans will likely continue to be selected by humans to be more tame and docile. This is an example of natural selection. d) The wolves living with humans will likely start to be selected by humans to be more ferocious. This is an example of artificial selection.

a) The wolves living with humans will likely continue to be selected by humans to be more tame and docile. This is an example of artificial selection.

Explain how genetic drift can lead to the elimination of an allele. a) Mutation within an allele could make it nonfunctional, causing it to lead to the death of any fetuses with that allele. This would remove the allele from the gene pool. b) Chance events such as a premature death or illness could make it impossible for individuals carrying recessive alleles to survive and reproduce. This would remove those alleles from the gene pool. c) A new allele that is introduced to a population through mutation could confer greater fitness than the existing allele, causing individuals with the original allele to reproduce less successfully. Over time, the original allele can be eliminated entirely. d) A new allele that is introduced to a population by an individual from another population could confer greater fitness than the existing allele, causing individuals with the original allele to reproduce less successfully. Over time, the original allele can be eliminated entirely.

b) Chance events such as a premature death or illness could make it impossible for individuals carrying recessive alleles to survive and reproduce. This would remove those alleles from the gene pool.

Describe natural selection and give an example of natural selection at work in a population. a) The process in which genes flow from one population to another. The beak size of Darwin's finches changing as the availability of different-sized seeds changes. b) The process in which better-adapted organisms are able to survive and reproduce; The beak size of Darwin's finches changing as the availability of different-sized seeds changes. c) The process in which better-adapted organisms are able to survive and reproduce; The Founder Effect occurring among humans immigrating to a new country. d) The process in which genes flow from one population to another. The Founder Effect occurring among humans immigrating to a new country.

b) The process in which better-adapted organisms are able to survive and reproduce; The beak size of Darwin's finches changing as the availability of different-sized seeds changes.

What would violate the conditions of Hardy-Weinberg equilibrium? a) random mating b) mutations c) large population d) no natural selection

b) mutations

Compare and contrast the bottleneck and founder effects. a) Both the bottleneck and founder effect change the genetic structure of a population. However, the bottleneck effect occurs when inbreeding depression kills off part of a population, whereas the founder effect relies on nonrandom mating. b) Both the bottleneck and founder effect change the genetic structure of a population. However, the bottleneck effect reduces or eliminates alleles within a population, whereas the founder effect introduces or increases alleles. c) Both the bottleneck and founder effect are examples of genetic drift. However, the bottleneck effect is a process in which a large portion of a genome is wiped out, whereas the founder effect occurs when members of a larger population migrate to establish their own population. d) Both the bottleneck and founder effect are examples of gene flow. However, the bottleneck effect occurs after a cataclysmic event, whereas the founder effect occurs when mutations introduce new alleles into a population.

c) Both the bottleneck and founder effect are examples of genetic drift. However, the bottleneck effect is a process in which a large portion of a genome is wiped out, whereas the founder effect occurs when members of a larger population migrate to establish their own population.

Which of the following is not an important role of population geneticists in ecology? a) Characterizing the emergence of new traits in a population b) Identifying changes in a population associated with changes in their habitat c) Determining the genetic diversity of populations d) Isolating the DNA mutation associated with an animal with a novel phenotype

c) Determining the genetic diversity of populations

The large alpha male elephant seal is constantly fending off the advances of medium sized males. Small males are then able to sneak copulation with females and successfully pass on their genes. What is this an example of? Explain. a) This is an example of genetic drift. Because there are so many medium-sized males to compete with the large alpha male, the small males are able to mate and cause the gene pool to shift towards smaller individuals. b) This is an example of directional selection. Because only the smallest males are mating, the next generation will have a higher proportion of alleles for small size, making the seals smaller over time. c) This is an example of diversifying selection, which is selection that favors extreme phenotypes. The sneaky males are favored in this case. d) This is an example of sexual selection. The females are selecting the small males over the large male.

c) This is an example of diversifying selection, which is selection that favors extreme phenotypes. The sneaky males are favored in this case.

Imagine you are trying to test whether a population of flowers is undergoing evolution. You suspect there is selection pressure on the color of the flower: bees seem to cluster around the red flowers more often than the blue flowers. In a separate experiment, you discover that blue flower color is dominant to red flower color. In a field, you count 600 blue flowers and 200 red flowers. What would you expect the genetic structure of the flowers to be? a) You would expect 300 homozygous dominant blue flowers, 300 heterozygous blue flowers, and 200 homozygous recessive red flowers. b) You would expect 14 homozygous dominant red flowers, 186 heterozygous blue flowers, and 600 homozygous recessive blue flowers. c) You would expect 200 homozygous dominant blue flowers, 400 heterozygous blue flowers, and 200 homozygous recessive red flowers. d) You would expect 100 homozygous dominant red flowers, 100 heterozygous red flowers, and 600 homozygous recessive blue flowers.

c) You would expect 200 homozygous dominant blue flowers, 400 heterozygous blue flowers, and 200 homozygous recessive red flowers.

Before the Industrial revolution light-colored moths were able to blend in with the environment and better avoid predators. Since the Industrial Revolution, dark-colored moths are better camouflaged than light-colored moths. The number of dark-colored moths has increased to be the most common color. This is an example of what? a) stabilizing selection b) frequency-dependent selection c) directional selection d) diversifying selection

c) directional selection

Describe an example of genetic drift. a) Introduction of new alleles through mutation can cause genetic drift. For example, if there are two alleles for fur color in a rabbit population, and a mutation in one of them produces a third allele, the gene pool changes to incorporate the new allele. b) Differential survival and reproduction can cause genetic drift. For example, if all the white rabbits in a population get eaten by wolves because their white fur stands out and is more visible, the proportion of the allele for white fur in the population will decrease. c) Immigration of new individuals can cause genetic drift. For example, if several white rabbits migrate into a population of mostly brown rabbits, the allele for white fur will increase within the population. d) Chance events such as a natural disasters can cause genetic drift. For example, if the only white rabbits in a population get killed by a storm, the allele for white fur will diminish or disappear in the population.

d) Chance events such as a natural disasters can cause genetic drift. For example, if the only white rabbits in a population get killed by a storm, the allele for white fur will diminish or disappear in the population.

The phenotype for a mouse is either dominant, (brown BB), or recessive, (white bb). If 40% of the mouse population is white, what is the percentage of mice in the population that are heterozygous? What is the frequency of homozygous dominant individuals? a) Heterozygous 14%, Homozygous dominant 47% b) Heterozygous 37%, Homozygous dominant 24% c) Heterozygous 27%, Homozygous dominant 34% d) Heterozygous 47%, Homozygous dominant 14%

d) Heterozygous 47%, Homozygous dominant 14%

How can evolutionary biologists use Hardy-Weinberg equilibrium while studying populations of organisms that they suspect may be evolving? a) Scientists can tell a population is evolving if the genotype frequencies are constant. b) Scientists can tell a population is evolving if the frequencies of homozygous dominant and homozygous recessive individuals are not equal. c) Scientists can tell a population is evolving if the frequencies of homozygous dominant and homozygous recessive individuals are equal. d) Scientists can tell a population is evolving if the allele frequencies change.

d) Scientists can tell a population is evolving if the allele frequencies change.

Large male cuttlefish attempt to acquire harems of breeding females, while very small male cuttlefish sneak into the harems by pretending to be females. What feature are the small males using to their advantage? a) Handicap principle b) Diversifying selection c) Positive frequency-dependent selection d) Sexual dimorphism

d) Sexual dimorphism

Trout inhabit a pond and are the main food for birds of prey in an area. The trout come in two colors: pink and silver. The pink are the brightest and easiest to see in the winter and are quickly picked off by the birds, allowing the number of silver trout to increase. When summer comes and the sun is out, the scales of the silver trout shine. The birds then begin to target the silver trout allowing the number of pink trout to increase. What type of selection is this? Explain. a) Sexual selection as one sex is preferred over the other. b) This is diversifying selection, because an extreme phenotype at one end of the spectrum is being selected over the other phenotype. c) This is stabilizing selection, because an intermediate phenotype is selected. d) This is directional selection, because an extreme phenotype at one end of the spectrum is being selected over the other phenotype.

d) This is directional selection, because an extreme phenotype at one end of the spectrum is being selected over the other phenotype.