BIO - Chapter 12

0.3

A particular gene in a population has two alleles, C and c. If the allele frequency of C = 0.7, what is the frequency of c? A.) 1.0 B.) 0.7 C.) 0.3 D.) 0.0 FEEDBACK: Allele frequencies must add up to 1.0 (all alleles). That is, all the alleles in a population have to add up to 100%. If the frequency of C is 0.7 (or 70%), that means the frequency of c must be 1 - 0.7 = 0.3 (or 30%).

Small population size

A population experiencing a genetic bottleneck would have which of the following characteristics? A.) Small population size B.) High mutation rates C.) High levels of gene flow D.) Sexual selection FEEDBACK: A genetic bottleneck involves a large reduction in population size, which can lead to genetic drift.

Disruptive selection

A species of bird lives in an area where large and small seeds are common, but medium size seeds are not. Birds with large beaks are adept at eating large seeds and birds with small beaks are adept at eating small seeds. This population will likely undergo A.) directional selection B.) stabilizing selection C.) disruptive selection D.) artificial selection FEEDBACK: Disruptive selection occurs when either extreme of the phenotype is preferentially selected for.

Genetic drift

A storm kills all of the plants on a hillside; the rest of the population is unharmed. The allele frequency of the alleles seen in the plants that do not live on the hill increases. This is an example of A.) gene flow B.) natural selection C.) genetic drift D.) the founder effect FEEDBACK: The organisms that survived did so due to random chance rather than adaptive traits, so the increase in their allele frequencies is also random. This is known as genetic drift.

Gene flow

A tourist brings home a small fish and releases it into a nearby lake. This fish is able to breed with fish already in the lake. The lake population is mainly orange and this fish is white. This is an example of A.) gene flow B.) a bottleneck C.) genetic drift D.) the founder effect FEEDBACK: Gene flow can occur when an organism travels to a new population and brings with it new alleles.

The founder effect

A tourist carries home a handful of seeds collected during a hiking trip. This species does not exist in the tourist's home area. These seeds germinate in the tourist's home area and establish a new population with traits that are uncommon in the plant's native area. This is an example of A.) artificial selection B.) a bottleneck C.) the founder effect D.) gene flow FEEDBACK: A founder effect occurs when a small group of individuals establishes a new population. In gene flow, alleles move into another pre-existing population.

Bat wings and bird wings.

An example of analogous traits are A.) bat wings and bird wings. B.) bat wings and whale fins. C.) human arms and chicken wings. D.) human arms and human legs. FEEDBACK: Analogous traits are similar characteristics that are the result of convergent evolution rather than descent from a recent common ancestor. Bats and birds have wings, but these evolved separately in response to similar environmental pressures.

250

Consider a mouse population with a total of 500 alleles for a specific gene. How many individuals are in this population? A.) 1,000 B.) 500 C.) 250 D.) 125 FEEDBACK: Because each diploid individual has two alleles, the number of individuals is half the total number of alleles in the population.

Conjugation tube

During horizontal gene transfer, a bacterium passes DNA to the recipient through a connection called a A.) plasmid B.) chromosome C.) gene flow tunnel D.) conjugation tube FEEDBACK: During horizontal gene transfer, a donor bacterium passes plasmid DNA through a conjugation tube to the recipient bacterium.

by receiving plasmid DNA from another species of bacteria.

It seems that vancomycin-resistant S. aureus (VRSA) acquired the resistance gene A.) through sexual reproduction B.) through mutation in the chromosomal DNA. C.) by receiving plasmid DNA from another species of bacteria. D.) when a genetic bottleneck killed most members of a non-resistant population. FEEDBACK: The evidence indicates that VRSA became resistant to vancomycin through horizontal gene transfer, in this case the movement of plasmid DNA from Enterococcus to S. aureus.

more like the current mean.

Several generations into the future, a population of birds currently undergoing stabilizing selection will look A.) less like the current mean. B.) more like the current mean. C.) more like one of the extremes. D.) more like both of the extremes. FEEDBACK: Stabilizing selection shifts the population extremes toward the mean, as individuals near the mean reproduce more than those toward the extremes, creating more individuals clustered around the mean.

can lead to physical differences between the males and females of a species.

Sexual selection in a population A.) can lead to physical differences between the males and females of a species. B.) always favors individuals with a higher survival potential. C.) does not lead to evolution. D.) reduces genetic variation in the population. FEEDBACK: Sexual selection occurs when a characteristic or set of characteristics makes individuals better at finding mates. When one sex prefers certain traits in a mate, this can result in the evolution of sexual dimorphism, or a large difference in the appearance of males and females of the same species. However, some of the characteristics that allow for better mating potential may actually be detrimental to survival.

usually random and unpredictable.

The evolutionary effects of genetic drift are A.) most obvious in large populations. B.) usually random and unpredictable. C.) always the same as those of natural selection. D.) shaped by nonrandom selective forces. FEEDBACK: Genetic drift is the random and unpredictable change in the genetic makeup of a population as a result of small population sizes or chance events.

the raw material of evolution

The genetic mutations that occur in organisms are A.) relatively rare events that have little consequence for evolution. B.) predictable by scientists before they actually occur. C.) directed toward a particular adaptive goal. D.) the raw material of evolution. FEEDBACK: Mutations are common events that are critical to evolution because they are the ultimate source of new alleles. They are not directed nor are they predictable.

maintaining the same color frequencies over time.

The population of crayfish on the left represents a population that is A.) drastically reduced in size by a natural disaster. B.) reproductivity isolated from all other populations. C.) maintaining the same color frequencies over time. D.) changing its allele frequencies due to the founder effect. FEEDBACK: In the population on the left, the color frequencies in the tank are similar to those in the bottle, so this population is not experiencing a change in allele frequencies over time. The population on the right, however, is experiencing a change in color frequencies due to the bottleneck effect.

Only organisms with the purple trait survive.

What does the following analogy demonstrate? A.) Only organisms with the yellow trait survive. B.) The purple organisms mutate to become yellow. C.) Only organisms with the purple trait survive. D.) The yellow organisms mutate to become purple. FEEDBACK: This analogy demonstrates that the environment (the strainer) will cause the yellow organisms to die; the purple organisms survive and reproduce.

15/30, or 1/2

What is the allele frequency of the white-fur-pigment allele? A.) 5/15, or 1/3 B.) 15/30, or 1/2 C.) 10/15 or 2/3 D.) 13/30 FEEDBACK: Allele frequencies must be calculated out of the total number of alleles in the population (30), not the total number of individuals (15). There are 15 white-fur-pigment alleles (white circles) out of 30 total alleles.

Allele frequencies in an individual change over time.

Which of the following is NOT a correct statement regarding the evolutionary process? A.) Random mutations and genetic rearrangement occur. B.) Natural selection acts on the genetic variation present in a population. C.) Inheritable characteristics are produced by random genetic events, such as mutation. D.) Allele frequencies in an individual change over time. FEEDBACK: Allele frequencies change in a population rather than in an individual. Individuals do not evolve, populations do.

Genetic drift

Which of the following is more likely to occur when a population of organisms is small? A.) Natural selection. B.) Mutation C.) Genetic drift D.) Random mating FEEDBACK: Genetic drift is the random change in allele frequencies that occurs when a population is small. It stems from the strong influence of chance events when there are few members of a population.

Saving leftover antibiotics to take for your next illness

Which of the following should you avoid to limit the spread of antibiotic resistance among pathogenic bacteria? A.) Getting vaccinated B.) Saving leftover antibiotics to take for your next illness C.) Taking the full course of an antibiotic when it is prescribed D.) Good hygiene and sanitation FEEDBACK: Saving leftover antibiotics contributes to the overuse of antibiotics, which can hasten the evolution of antibiotic-resistant bacteria. Antibiotics should only be taken when prescribed.

It reduces the genetic variation between different populations.

Which of the following statements about gene flow is true? A.) It reduces the genetic variation within a single population. B.) It reduces the genetic variation between different populations. C.) It reduces the movement of alleles between populations. D.) It rarely occurs in natural populations. FEEDBACK: Gene flow moves alleles between populations, thus making those populations more alike genetically.

Mutation is the ultimate source of new alleles.

Which of the following statements about genetic variation is true? A.) Mutation is the ultimate source of new alleles. B.) The only source of genetic variation is gene transfer. C.) New alleles are only formed during sexual reproduction. D.) Mutations that occur in skin cells can be inherited. FEEDBACK: Mutation is the only source of new alleles and a major source of genetic variation. Only mutations in gametes can be inherited.