Question 1

Insecticides are used to kill insects.However,insecticide-resistant insects are being found.What is the mechanism for this new insect trait?

Accepted Answer

Insecticide-resistant insects likely arise through a process of natural selection. When exposed to insecticides, most insects will die, but a few with a random mutation that provides resistance to the insecticide will survive. These resistant insects will then reproduce and pass on the resistance to their offspring, leading to an increasing frequency of the resistance trait in the population. Over time, the majority of insects in the population may become resistant to the insecticide, rendering it ineffective.

Question 2

Evolutionary changes occur when ________ acts upon populations containing individuals with genetic differences.

Accepted Answer

Evolutionary changes occur when natural selection acts upon populations containing individuals with genetic differences. Natural selection is the process by which organisms with traits better suited for their environment survive and reproduce more successfully than those without these traits, leading to a gradual change in the characteristics of a population over time. Continental drift, weather, and mutation may also play a role in evolution, but they are not the direct mechanism by which evolutionary changes occur.

Question 3

Two different species may have similar features because of

Accepted Answer

Similar features in two different species are generally attributed to a common ancestor. This is because when two species diverge from a common ancestor, they may retain certain traits even if they evolve in different ways. This is known as homology, and it is the basis for much of modern evolutionary biology. Genetic drift, the founder effect, and bottlenecks can all cause changes in the frequency of certain traits within a population, but they are unlikely to create similar features in two entirely different species.

Question 4

Disruptive selection operates whenever

Accepted Answer

Disruptive selection favors both extremes of a phenotype, leading to the splitting of a population into two distinct groups. This can result in the evolution of new species in the long term.

Question 5

An example of evolution that has been readily observed is

Accepted Answer

Increased resistance of bacteria to an antibiotic is an example of evolution that has been readily observed. Bacteria can evolve and develop resistance to antibiotics over time. This is because bacteria reproduce at a rapid rate, allowing for rapid changes in their genetic makeup. As a result, the use of antibiotics can lead to the survival and reproduction of bacteria with antibiotic resistance genes, ultimately leading to the evolution of new strains of bacteria. This has been observed in many different types of bacteria and is a well-documented example of evolution in action.

Question 6

Alex is a student with Strep throat (caused by a strain of bacterium)who is given a prescription for an antibiotic and is told to take the drug for two weeks.After a week,he feels better and stops taking the drug.Two months later,Alex again shows symptoms of Strep throat and decides to finish the leftover antibiotic rather than going to the doctor again.Two months after that,he develops Strep throat for a third time and returns to the doctor.This time,the antibiotic does not work.The doctor runs a test and discovers that the bacterial strain Alex is carrying is antibiotic resistant.What most likely happened?

Accepted Answer

When Alex stopped taking the antibiotic in the middle of the prescribed course, some of the bacteria that were more drug resistant would have survived and repopulated his throat. Over time, the drug-resistant alleles would have become more common, eventually leading to a strain that is resistant to the antibiotic. This is a common cause of antibiotic resistance in bacteria.

Question 7

New alleles arise by

Accepted Answer

New alleles arise by mutation, which is a random error in DNA replication that results in a new genetic variant not previously present in the population. Nonrandom mating can affect the distribution of existing alleles, but does not create new ones. Allele frequency refers to the proportion of existing alleles in a population, not the creation of new ones. Genetic drift is a random change in allele frequency due to chance events in small populations, but it does not create new alleles.

Question 8

Jean-Baptiste Lamark proposed that populations evolve when traits acquired during the lifetime of a parent are passed down to offspring.What is wrong with this proposal?

Accepted Answer

Lamarck's proposal, also known as the inheritance of acquired characteristics, is not supported by modern genetics. Only changes in the DNA sequence of an organism can be inherited, while traits acquired throughout life generally do not involve changes to DNA. Therefore, traits that are acquired during an individual's lifetime cannot be passed down to offspring.

Question 9

In natural selection,________ that increase survival and reproductive success become more common in a population.

Accepted Answer

Natural selection acts on phenotypes, or the observable traits of an individual, in order to increase their chances of surviving and reproducing. This can result in certain phenotypes becoming more common over time, as they are passed down to offspring and spread throughout the population. While genotypes and allele frequencies can also play a role in natural selection, it is ultimately the phenotype that determines an individual's ability to survive and reproduce in their particular environment. Bottlenecks, on the other hand, refer to a temporary reduction in genetic diversity within a population and do not directly relate to natural selection.

Question 10

Two unrelated species evolving to look more similar due to environmental pressures is called

Accepted Answer

Convergent evolution is when two unrelated species evolve to look more similar due to similar environmental pressures. This can result in similar physical appearance or adaptations even though the two species are not closely related genetically. Gene flow is the exchange of genes between populations, genetic drift is a random change in the frequency of alleles in a population, and divergent evolution is when two related species evolve to become more different over time. None of these describe the scenario of two unrelated species becoming more similar due to environmental pressures.

Question 11

Convergent evolution occurs when natural selection causes distantly related organisms to

Accepted Answer

Convergent evolution occurs when distantly related organisms evolve similar structures in response to similar environmental challenges. This results in analogous structures (similar function but different evolutionary origin) rather than homologous structures (similar function and evolutionary origin).

Question 12

When robins lay a clutch of more than four eggs,their chicks are often malnourished because they have so many to feed.If the robins lay fewer than four eggs,they may not have any viable offspring.As a result,robins typically lay a clutch of four eggs.This is an example of

Accepted Answer

Stabilizing selection favors the average characteristic and eliminates the extremes. In this case, laying a clutch of four eggs is the average and most successful strategy for robins, as it maximizes the chances of having viable offspring while also avoiding malnourishment of the chicks due to competition for resources.

Question 13

The color of a certain species of beetle is determined by a single gene.Two beetles homozygous for green coloration (meaning they have two copies of the green allele)produce a single offspring with brown coloration.Brown color appeared in this offspring as a result of

Accepted Answer

The appearance of brown coloration in the offspring of two green-colored parents indicates a mutation has occurred. This mutation likely affected the gene responsible for determining the coloration of the beetle, resulting in a change from the green allele to the brown allele.

Question 14

Which of the following is true with regard to mutations?

Accepted Answer

Mutations can occur spontaneously without any external pressure or influence. They can arise from errors during DNA replication or from exposure to mutagens, but they are not necessarily a direct response to environmental pressures.

Question 15

Several related bird species live in a desert.One species is much smaller than the other species.This small species nests in holes in cacti.Because the bird is so small,it can easily squeeze between the spines of the cactus and create a well-protected nest.This is an example of

Accepted Answer

This is an example of natural selection because the small size of the bird allowed it to adapt to its environment by nesting in a protected area. Over time, this trait would continue to be selected for through the process of natural selection.

Question 16

In a shallow bay,a population of oysters is the food source for the local crabs.The lightest colored oysters blend with the color of the rocks and the darkest colored oysters are concealed in the shadows cast by the rocks.Oysters with an intermediate coloring are easily detected by the crabs and become a tasty meal for them.Over time,fewer and fewer oysters display the intermediate coloring while more oysters are either the lightest coloring or the darkest coloring.This is an example of

Accepted Answer

This is an example of disruptive selection because it favors the extreme phenotypes (lightest and darkest colored oysters) over the intermediate phenotype. This results in a bimodal distribution of oyster coloration and ultimately reduces the number of intermediate colored oysters in the population.

Question 17

The population of a cactus species in a particular area has two to seven spines with an average of four spines per square centimeter of surface area.Cacti with fewer than four spines per square centimeter are more easily eaten by the wild boars thriving in the area.Over time,the population of this cactus species in this area have an average of six spines per square centimeter of surface area.This is an example of

Accepted Answer

The increase in average number of spines suggests that natural selection favored cacti with more spines, which would be resistant to wild boar predation. This is an example of directional selection.

Question 18

Evolution can be described as

Accepted Answer

Evolution is a gradual change in the genetic characteristics of a population of organisms over time through natural selection, mutation, genetic drift, and migration. It is not designed or predetermined, but rather a result of environmental pressures and chance events. B is incorrect because sudden shifts in an individual's genetic characteristics would not necessarily result in evolutionary change in the population. D is incorrect because although geologic forces can cause isolation of populations, this is not the definition of evolution.

Question 19

When individuals with intermediate values of an inherited phenotypic trait,like head circumference at birth,have an advantage over other individuals in the population,________ is the apparent pattern of natural selection.

Accepted Answer

Stabilizing selection favors individuals with intermediate phenotypes, often leading to a decrease in population variation for the trait in question without changing the mean of the trait. This is because individuals with extreme values of the trait are selected against, while those with values closer to the population mean are more likely to survive and reproduce.

Question 20

Which of the following is NOT a mode of natural selection?

Accepted Answer

Directional selection, disruptive selection, and stabilizing selection are all well-documented modes of natural selection. However, "dormant selection" is not a recognized mode of natural selection. It is possible that this is simply a term that has been made up, as "dormant" does not seem to fit well within the context of natural selection.

Quiz 12: Mechanisms of Evolution