Evolutionary Science Quiz

Natural selection is the process by which certain traits or characteristics become more or less common in a population over time. It occurs when individuals with certain advantageous traits are more likely to survive and reproduce, passing on those traits to future generations. This leads to a gradual change in allele frequencies within a population, as individuals with beneficial alleles have a higher chance of passing them on. Therefore, natural selection is the evolutionary process that accounts for the most changes in allele frequencies compared to other processes such as genetic drift or gene flow.

The three models of natural selection are directional, stabilizing, and disruptive. Directional selection occurs when individuals with extreme traits have a higher fitness and are favored by natural selection, causing the population to shift towards that extreme trait. Stabilizing selection occurs when individuals with intermediate traits have a higher fitness, leading to a reduction in the variation of the population. Disruptive selection occurs when individuals with extreme traits at both ends of the spectrum have a higher fitness, resulting in the population being divided into two distinct groups.

Inbreeding is a severe form of non-random mating that typically occurs in small populations. It involves the mating of individuals who are closely related, such as siblings or cousins. This leads to an increased occurrence of homozygous recessive individuals, as the chances of inheriting two copies of the same recessive allele are higher when mating with a close relative. Homozygous recessive individuals have two copies of the same recessive allele, which can result in the expression of harmful or deleterious traits.

Gene flow refers to the movement of alleles (different forms of a gene) into or out of a population when individuals migrate or disperse. It can occur when individuals from one population migrate and join another population, bringing their alleles with them, or when individuals leave a population, taking their alleles with them. This process can introduce new genetic variation into a population or reduce existing variation, depending on the characteristics of the migrating individuals. Gene flow is an important mechanism for genetic exchange between populations and can have significant impacts on the genetic structure and diversity of populations.

The correct answer is Founder Effect. The Founder Effect occurs when a small number of individuals leave a population and establish a new isolated population. As a result, the smaller number of individuals cannot contain all the genetic diversity present in the parent population. This leads to a loss of genetic variation and the new population becomes genetically different from the original population.

Genetic drift refers to the random changes in the frequency of alleles in a population over time. It is a result of chance events rather than natural selection. In small populations, genetic drift can have a significant impact and may lead to the loss of beneficial alleles. This occurs because random events, such as the death or failure to reproduce of individuals carrying these alleles, can cause their frequency to decrease. Therefore, when genetic drift occurs, beneficial alleles may be eliminated from the population.

A cline is a graded series of changes in some characteristics that are correlated with a gradual change in an environmental factor over the geographic range of a species. This means that as the environmental factor changes across different regions, the characteristics of the species also gradually change. A cline can be observed in various traits such as body size, coloration, or behavior, and it represents the adaptation of a species to different environmental conditions.

Directional selection occurs when there is a shift in the average phenotype of a population towards one extreme due to environmental changes. This means that individuals with traits closer to the extreme end of the spectrum are favored and have higher fitness. As a result, the frequency of these traits increases in the population over time, leading to a change in the overall phenotype. This type of selection is commonly observed in response to factors such as changes in temperature, food availability, or predation pressure.

Disruptive selection is the model of natural selection that results in dimorphism or polymorphism. In this type of selection, extreme traits are favored over intermediate traits, leading to the divergence of a population into two or more distinct phenotypes. This can result in the development of different forms or colors within a species. Individuals with extreme traits have a higher fitness and are better adapted to different environmental conditions, allowing them to survive and reproduce more successfully. Over time, this can lead to the establishment of distinct populations with different traits.

The Hardy-Weinberg equilibrium is used to predict genetic changes in a population over time. This principle assumes that certain conditions are met, such as no mutation, migration, natural selection, random mating, and a large population size. In an equilibrium state, allele frequencies remain constant from generation to generation. By studying the equilibrium, scientists can make predictions about how genetic traits will be inherited and distributed within a population over time.

During non-random mating, sexual dimorphism occurs which means due to differences in appearances (like feather color) females will select the most fit mate. Sexual dimorphism refers to the physical differences between males and females of the same species. In this case, females are choosing mates based on their appearance, such as feather color, which indicates their fitness. This selective process ensures that the most fit mates are chosen, leading to the continuation of desirable traits in the population.

A population bottleneck refers to a drastic and abrupt decrease in the size of a population. This can occur due to natural disasters or habitat loss, which greatly reduce the number of individuals in the population. As a result of this sudden reduction, the genetic diversity within the population is also reduced. This leads to a random alteration of allele frequencies, as certain alleles may be lost or become more prevalent in the remaining population.