Genes Within Populations: Chapter 20

In a small, isolated population of wildflowers, you observe a shift in allele frequencies for flower color simply due to chance events. This is an example of:

A population of birds exhibits a wide range of beak sizes. Over several generations, the average beak size shifts towards larger beaks due to a drought leading to larger, tougher seeds. This is an example of:

Male deer compete with each other using their antlers to win mating opportunities with females. This is an example of:

In a certain species of fish, individuals with a rare color pattern are better able to avoid predators because the predators haven't learned to recognize them. As the rare color pattern becomes more common, predators begin to target it, and its advantage decreases. This is an example of:

A population of butterflies experiences a cycle where brown coloration is advantageous during dry seasons due to camouflage on dead leaves, while green coloration is favored during wet seasons when foliage is lush. This is an example of:

In a population, individuals who are heterozygous for a particular gene have a higher survival rate than individuals who are homozygous. This phenomenon is known as:

A gene that affects both disease resistance and bone density exhibits:

In a scenario where the expression of one gene is masked or altered by the expression of another independent gene, this is an example of:

How does genetic variation contribute to the process of evolution?

In the context of population genetics, what is the most accurate definition of 'evolution'?

According to Darwin's theory of natural selection, what factor primarily determines which individuals will survive and reproduce?

What does it mean for a population to be in Hardy-Weinberg equilibrium?

Which condition is NOT a requirement for a population to be in Hardy-Weinberg equilibrium?

How does the process of gene flow affect the genetic diversity of populations?

If a population is experiencing a higher-than-expected rate of mutation, what is the likely long-term effect on the population's genetic variation and allele frequencies?

Which of the following scenarios best illustrates natural selection?

Consider a population of tetraploid wheat undergoing autopolyploidy. A novel disease resistance allele arises on one chromosome. Assuming preferential pairing during meiosis resulting in disomic inheritance, and given an initial allele frequency of $p = 0.01$, what is the expected frequency of homozygous resistant individuals ($RRRR$) after 10 generations of random mating, neglecting selection and mutation?

In a population of organisms with overlapping generations, where generation time is environmentally determined and varies significantly among individuals, what methodological challenge arises when attempting to measure allele frequency changes across multiple generations?

A researcher is studying a population of plants where seed dispersal is limited, leading to increased relatedness among neighbors. How does this non-random spatial distribution likely influence the efficacy of selection, and what evolutionary outcome is most probable?

Consider a scenario in which a population bottlenecks due to a catastrophic event, reducing its size to a few individuals. After the population recovers, the frequency of a previously rare deleterious allele is now significantly higher. Which of the following evolutionary mechanisms best explains this phenomenon, and what are its long-term implications for the population's fitness?

In a species of migratory birds, two distinct breeding populations exist, each adapted to different environmental conditions. However, some individuals occasionally migrate to the 'wrong' breeding site and interbreed. What evolutionary process is most directly affected by this phenomenon, and what is its likely impact on the genetic divergence between these populations?

A population of insects is exposed to a novel insecticide. Initially, only a few individuals possess a resistance allele. Over time, the frequency of this allele increases dramatically. How would you differentiate between a scenario where the resistance allele was already present in the population at low frequency versus one where the insecticide directly induced the mutation conferring resistance?

Consider a population undergoing cyclical environmental changes that alternately favor two different phenotypes. How would you expect this fluctuating selection regime to impact the overall genetic diversity in the population compared to a scenario with constant selection for a single phenotype?

In a scenario where two previously isolated populations of the same species come into secondary contact, what factors will determine whether they merge into a single panmictic population or maintain reproductive isolation, potentially leading to speciation?

Assuming a population of organisms with a continuous distribution of phenotypic traits is subjected to disruptive selection, what is the expected long-term effect on the genetic variance of these traits within the population, and how might this influence the potential for future evolutionary change?

If a population of plants is subjected to strong selection pressure favoring self-pollination over cross-pollination, how would you expect the genome-wide heterozygosity to change over several generations, and what are the potential evolutionary consequences of this shift in mating system?

Consider a metapopulation of a critically endangered amphibian species inhabiting a fragmented landscape. Patches vary significantly in size, resource availability, and degree of isolation. A novel, highly virulent pathogen is introduced into one of the larger patches. Which of the following scenarios would MOST likely result in the extirpation of the entire metapopulation, considering interactions between genetic drift, gene flow, and natural selection?

A population of deep-sea vent extremophiles exhibits a unique form of oscillating selection based on the cyclical eruption patterns of hydrothermal vents. During eruption phases, thermophilic genotypes are favored due to increased environmental temperatures. Conversely, during dormant phases, barophilic genotypes are favored due to increased hydrostatic pressure. Given a scenario where the frequency of vent eruptions becomes increasingly erratic and unpredictable due to anthropogenic climate change, what is the MOST likely long-term evolutionary outcome for this population?

In a theoretical model incorporating both inter- and intrasexual selection within a lek mating system, assume that male display traits (e.g., elaborate plumage, vocalizations) are condition-dependent, reflecting underlying genetic quality and immune competence. However, females also assess male fighting ability during brief, ritualized contests on the lek. If a novel, highly contagious, and debilitating disease is introduced into the population, which of the following scenarios is the MOST plausible evolutionary outcome?

Consider a scenario of negative frequency-dependent selection acting on a shell coiling direction polymorphism (dextral vs. sinistral) in a snail population subject to predation by birds with a learned search image. Initially, sinistral snails are rare and thus experience lower predation rates. However, as sinistral snails become more common, predators increasingly target them. If a co-occurring parasitic trematode preferentially infects dextral snails, inducing gigantism and reduced mobility specifically, how will this impact the equilibrium frequency of sinistral snails?

A population of migratory songbirds exhibits a genetically determined preference for specific wintering grounds. Birds that winter in region A experience higher survival rates but lower reproductive success due to limited resources. Conversely, birds wintering in region B exhibit lower survival but increased reproductive opportunities. If a climate change-induced shift in resource availability drastically alters the carrying capacity of region A, favoring earlier arrival and prolonged, what is the most likely evolutionary response? (Assume arrival time is also genetically determined.)

A population of plants is known to have both pleiotropic and epistatic gene interactions, influencing traits related to drought tolerance (root depth, leaf surface area) and pathogen resistance (production of antimicrobial compounds). Imagine that the region where the plants live experiences increased drought and a novel fungal pathogen outbreak. Given the constraints imposed by pleiotropy and epistasis, what evolutionary outcome is MOST probable?

Imagine that a scientist is studying gene flow in a group of isolated islands with distinct, endemic populations of lizards. Islands are connected by rare, stochastic dispersal events (e.g., lizards rafting on storm debris). The scientist notices that a specific allele, initially rare on a particular island, rapidly increases in frequency after a single such dispersal event, despite not conferring any obvious selective advantage in the new environment. What is the MOST likely explanation.

Consider a scenario in which a previously isolated population of birds experiences a sudden influx of individuals from a genetically distinct, larger population due to habitat fragmentation and forced migration. The resident population was well-adapted to its local environment, but the migrants carry alleles that are maladaptive in this setting. What evolutionary trajectory is MOST likely to occur in the admixed population immediately following this gene flow event, assuming that selection pressures remain constant?

In a species of annual plant with non-overlapping generations, seed dormancy is a bet-hedging strategy against unpredictable environmental fluctuations. Seeds can either germinate immediately or remain dormant in the soil seed bank for one or more years. In a climate change scenario characterized by increasingly frequent and severe droughts, how would you expect selection to act on the seed dormancy trait, considering its effect on both short-term and long-term population viability?

A researcher is studying a small, isolated population of island foxes. They observe a rare coat color morph that appears to confer a slight advantage in camouflage against a novel, introduced predator. However, the allele frequency for this coat color remains stubbornly low despite the selective advantage. Which of the following factors could MOST plausibly explain this persistent low frequency, even with ongoing selection?

Genetic Variation

Evolution

Natural Selection

Allele Frequency

Hardy-Weinberg Principle

Agents of Evolutionary Change

Mutation

Gene Flow

Genetic Drift

Nonrandom Mating

Sexual Selection

Intrasexual Selection

Heterozygote Advantage

Frequency-dependent Selection

Pleiotropy

Genetic Variation Importance

Evolution Definition

Natural Selection Process

Hardy-Weinberg Equilibrium Criteria

Hardy-Weinberg Equation

Mutation Role

Gene Flow Effect

Genetic Drift Definition

Nonrandom Mating Influence

Sexual Selection Concept

Quantifying Natural Selection

Reproductive Strategies

Negative Frequency-dependent Selection

Oscillating Selection

Guppy Color Patterns Study

Gene Flow vs. Local Adaptations

Epistasis

Limited Genetic Variation

Importance of Genetic Diversity