AP Bio Ch 19 Quiz

Gene mutation occurs randomly and can happen at any time, regardless of whether it provides any advantage or benefit to the organism. This means that mutations can occur even if they do not improve the organism's ability to survive or reproduce. Therefore, the statement is true.

The statement is true because the founder effect refers to a situation where a small group of individuals founds a new population, resulting in a limited genetic diversity. In the case of the Amish population in Pennsylvania, their ancestors were a small group of individuals who migrated and settled in the area, leading to a restricted gene pool. As a result, certain unusual genes or genetic disorders can be found in high frequencies within the isolated population. This is a classic example of the founder effect.

The statement is false because the Hardy-Weinberg equilibrium assumes that certain conditions are met, such as a large population size, random mating, no migration, no natural selection, and no mutation. In reality, most populations are subject to changing environments which can disrupt these conditions and prevent the population from being in Hardy-Weinberg equilibrium. Therefore, the statement that the equilibrium is usually met in most populations in changing environments is incorrect.

The bottleneck effect refers to a phenomenon where a population undergoes a drastic reduction in size, resulting in a limited gene pool and decreased genetic diversity. In the case of cheetahs, it is believed that a bottleneck event occurred in their evolutionary history, leading to a significant decrease in their genetic variability. This reduction in genetic diversity can have negative consequences, including reduced fertility and increased vulnerability to diseases and environmental changes. Therefore, it is true that the bottleneck effect is thought to be responsible for the loss of variability and fertility in the cheetah species.

A population refers to all the individuals of a single species that live in a specific area at the same time. It includes all the individuals of the species, regardless of their age, sex, or reproductive status. A population is a fundamental unit of study in ecology and is important for understanding the dynamics and interactions within a species in a given area.

The statement is false because industrial melanism in peppered moths in England is actually an example of directional selection, not stabilizing selection. Stabilizing selection occurs when the extremes of a trait are selected against, leading to the average phenotype being favored. In the case of peppered moths, the dark-colored melanic form became advantageous in polluted industrial areas, leading to an increase in its frequency and a decrease in the light-colored form. This is a clear example of directional selection, where one extreme of the trait is favored over the other.

Genetic drift refers to the random changes in allele frequencies in a population over time. It is more likely to occur in small populations because chance events can have a greater impact on allele frequencies. When genetic drift occurs, it can lead to the loss of an allele from a population, causing the remaining allele to become fixed. This means that all individuals in the population will have the same allele for that particular gene. Therefore, the statement that genetic drift may lead to an allele's becoming fixed in a population when its alternative allele is lost from the population is true.

Drug-resistance mutations can occur in bacteria at any time, even when they are not exposed to the drug. This is because mutations can happen spontaneously in the bacterial DNA, leading to the development of resistance to certain drugs. These mutations can occur due to various factors such as errors during DNA replication or exposure to environmental stressors. Therefore, bacteria can acquire drug resistance even in the absence of drug exposure, making the given answer the correct explanation.