Table of Contents
Does frequency-dependent selection preserve genetic variation?
Positive frequency-dependent selection favours common alleles, accelerates the loss of rare alleles and decreases genetic variation. … Host antibodies target the most common antigens, and frequency-dependent selection preserves genetic diversity of antigens of parasites and antibodies of their hosts.
Is balancing selection frequency-dependent?
Frequency-dependent selection is a dynamic form of balancing selection that occurs when the fitness of a given phenotype increases, or decreases, based on its prevalence relative to alternative phenotypes within a population.
Can frequency-dependent selection maintain multiple alleles?
Intuitively, negative frequency dependence (selection against common alleles) should be good at maintaining many alleles at a locus. Conversely, one would expect positive frequency dependence (selection for common alleles) to result in monomorphism.
How does negative frequency-dependent selection help maintain variation?
Negative frequency-dependent selection has the potential to maintain polymorphisms within populations because relatively rare variants have a selective advantage over more common variants and thus tend to increase in frequency and avoid local extinction.
What is frequency-dependent selection in biology?
Frequency-dependent selection is defined as a situation where fitness is dependent upon the frequency of a phenotype or genotype in a population. Our focus here is on negative frequency-dependent selection, whereby fitness of a phenotype or genotype increases as its frequency in a population decreases.
What is frequency independent selection?
Selection is called frequency independent if the fitness of a genotype does not depend on the frequencies of the other genotypes in the population. If constant selection acts on a haploid population, each haploid genotype (haplotype) has an externally determined fitness value.
What is an example of frequency-dependent selection?
Frequency-dependent selection occurs when the fitness of a genotype depends on its frequency. … Examples of frequency dependence can arise in systems of mimicry: Natural selection may favor non-poisonous butterflies that have the same color pattern as poisonous butterflies.
What is the difference between balancing and disruptive selection?
Balancing selection keeps two or more alleles at intermediate frequencies and prevents fixation. … Disruptive selection can fix either allele, if its frequency is already high enough.
How does balancing selection differ from frequency-dependent selection?
One type of balancing selection is the heterozygote advantage. … Frequency-dependent selection is another type of balancing selection. This is when selection acts against a specific phenotype when it becomes too common. The phenotype that is less common often holds the advantage because it is less common.
How does selection affect gene frequency?
Explanation: Natural selection decreases the frequency in a population of genes that decrease fitness and increases the frequency of genes that increase fitness. **Note that fitness in ecology refers to an individual’s ability to survive and produce viable offspring.
Why does the fitness of phenotype depend on frequency-dependent selection?
In frequency-dependent selection the fitness of a phenotype depends on how common it is in the population. … Prey species protect from whichever scale eating fish is most common hence selecting against that particular phenotype. As a result, the frequency of each phenotype oscillates over time.
What is positive frequency-dependent selection?
Positive frequency-dependent selection (FDS) is a selection regime where the fitness of a phenotype increases with its frequency, and it is thought to underlie important adaptive strategies resting on signaling and communication.
Does negative selection reduce genetic diversity?
Consequences of Negative Selection If the best-adapted variant does not change because it is at a stable local optimum, then negative selection will remove all new variants for that optimal trait. It is important to note that negative selection can also impact molecular diversity.
What is positive selection in genetics?
Positive natural selection, or the tendency of beneficial traits to increase in prevalence (frequency) in a population, is the driving force behind adaptive evolution.
Is Batesian mimicry positive or negative frequency-dependent selection?
Batesian mimicry can be under positive selection because of the protection gained against predators, due to resemblance to unpalatable model species.
What is an example of stabilizing selection?
Stabilizing selection in evolution is a type of natural selection that favors the average individuals in a population. … Classic examples of traits that resulted from stabilizing selection include human birth weight, number of offspring, camouflage coat color, and cactus spine density.
What is an example of intersexual selection?
Intersexual selection occurs as a result of interactions between males and females of a species. One sex, typically males, will develop and display traits or behavior patterns to attract the opposite sex. Examples of such traits include plumage on birds, the mating calls of frogs, and courtship displays in fish.
What does Underdominance mean in biology?
Underdominance is classically defined as the genetic condition where the fitness of heterozygote individuals is lower than the fitness of both of the parental homozygotes (Hartl and Clark 1989). There are two stable and one unstable equilibria in such a system with two alleles.
What is inverse frequency dependent selection?
Frequency-dependent selection is an evolutionary process by which the fitness of a phenotype or genotype depends on the phenotype or genotype composition of a given population. … In negative frequency-dependent selection, the fitness of a phenotype or genotype decreases as it becomes more common.
What does the frequency depend on?
The actual frequency is dependent upon the properties of the material the object is made of (this affects the speed of the wave) and the length of the material (this affects the wavelength of the wave).
What is independent selection?
Independent Selection is a selection strategy whereby a genotype is selected if it has an outstanding level for a single trait (breeding objective), regardless of its levels on other traits.
What is an example of disruptive selection?
Disruptive Selection Examples: Color Light-colored oysters would blend into the rocks in the shallows, and the darkest would blend better into the shadows. The ones in the intermediate range would show up against either backdrop, offering those oysters no advantage and make them easier prey.
Is Mullerian mimicry frequency-dependent?
Mllerian mimicry and warning color are standard textbook examples of frequency-dependent selection within species (e.g. 99, 126) as well as leading to Mllerian mimicry between species (103).
What is the result of directional selection?
Directional selection: Directional selection occurs when a single phenotype is favored, causing the allele frequency to continuously shift in one direction. … The result of this type of selection is a shift in the population’s genetic variance toward the new, fit phenotype.
How does balancing selection work?
Balancing selection means that two alleles are maintained in the population because of natural selection. … This means that the fitness of an individual with two different versions of the allele is higher than the fitness of an individual with two copies of one of the alleles.
What are the three types of selection?
The 3 Types of Natural Selection
- Stabilizing Selection.
- Directional Selection.
- Disruptive Selection.
How are heterozygote advantage and frequency dependent selection both examples of balancing selection?
balancing selection (balanced polymorphism): 2 or more alleles are maintained in a population due to selection. Both heterozygote advantage and frequency dependent selection are examples of balancing selection, they both lead to a stable polymorphic equilibrium state.
What do you mean by balancing selection?
Balancing selection occurs when multiple alleles are maintained in a population, which can result in their preservation over long evolutionary time periods. A characteristic signature of this long-term balancing selection is an excess number of intermediate frequency polymorphisms near the balanced variant.
What is the advantage of heterozygosity?
Heterotic balance (heterozygous advantage) polymorphisms develop when the fitness of heterozygotes is higher than the fitness of both homozygotes in a given population. A classic case of balanced polymorphism in human populations is sickle cell anemia.
Does negative frequency dependent selection increase genetic variation?
Negative frequency-dependent selection serves to increase the population’s genetic variance by selecting for rare phenotypes, whereas positive frequency-dependent selection usually decreases genetic variance by selecting for common phenotypes.