AP Biology : Population Genetics

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #291 : Evolution And Genetics

Select the best example of the bottleneck effect.

Possible Answers:

Drought causes a local lake to shrink drastically. Eagles catch and eat nearly all the fish before seasonal rains replenish the level of the lake. The fish population eventually returns to its original numbers.

During a flash flood a small group of fish inhabiting a river are able to swim through the flood waters to a nearby lake where they remain when the waters subside. This group of fish eventually dominates the lake which previously was home to smaller fish.

A fungus nearly wipes out all of a farmer's pea plants. Later the farmer learns from a botanist that the survivors possessed a gene that made those pea plants grow a thicker cuticle causing the fungus to be unable to take hold and kill the plant.

None of these

A pair of wolves (1 male and 1 female) are released into a large national park to reduce the population of deer. The wolves prosper in their new prey-rich environment and eventually establish a larger wolf population. 

Correct answer:

Drought causes a local lake to shrink drastically. Eagles catch and eat nearly all the fish before seasonal rains replenish the level of the lake. The fish population eventually returns to its original numbers.

Explanation:

The bottleneck effect occurs when a random and catastrophic event reduces the population of an organism by a large number. The remaining individuals repopulate the area after the event, but the genetic diversity of the population is greatly reduced. The founder effect occurs when a group of individuals are separated from the main population and subsequently establish a new population. This new population's genetic diversity is also greatly reduced.  In both cases a small number of individual establish a population and this small "pool" of genes is how genetic diversity is reduced. The wolves are separated from their pack by being released in a new area and then established a new population; this is an example of the founder effect. The pea plants were killed by a random event, but the survivors did not survive by random chance. Instead they had a gene that gave them higher fitness compared to the other members. This is a better example of natural selection. The fish in the flash flood were separated from the main population and subsequently established a new population in the nearby lake. This is an example of the founder effect. The drought lake is the best example of the Bottleneck effect because the event was random and the survivors lived due to random chance. A small number of the fish reestablished their population in the lake, their genetic diversity was also reduced.

Example Question #2231 : Ap Biology

Which of the following is true regarding genetic drift?

Possible Answers:

All of these

Genetic drift reduces genetic variation

It is the change in allele frequency due to sampling error

Effect of genetic drift is less in larger populations

Correct answer:

All of these

Explanation:

Genetic drift is a change in allele frequency between generations due to sampling error. Since genetic drift makes certain allele variations disappear, it decreases genetic variation. Additionally, genetic drift has a smaller effect in larger populations and a large effect in small populations.

Example Question #11 : Understanding Genetic Drift, Bottleneck Effect, And Founder Effect

Which of the following is an example of gene flow?

Possible Answers:

Migration

Neither migration nor horizontal gene transfer

Both migration and horizontal gene transfer

Horizontal gene transfer

Correct answer:

Both migration and horizontal gene transfer

Explanation:

Gene flow is a mechanism of evolution in which genes are transferred between populations. Two examples of gene flow are migration and horizontal gene transfer. In the case of migration, the movement of individuals into or out of a population also results in a transfer of alleles. Horizontal gene transfer (common in bacteria) is the transfer of genes through means other than reproduction (i.e. plasmid exchange).

Example Question #41 : Population Genetics

Evolution that occurs within a population due to the production of a finite number of zygotes from a given gene pool is referred to as which of these?

Possible Answers:

Loss of heterozygosity

Natural selection

Genetic drift

Inbreeding depression

The Fonder Effect

Correct answer:

Genetic drift

Explanation:

Genetic drift is due to the production of a finite number of zygotes within a population. This causes allele frequencies to change from one generation to the next. Genetic drift can result in the reduction of the fitness of individuals within a population if the alleles passed on are deleterious.

Example Question #2231 : Ap Biology

When a population is reduced for a short period of time, and only rare alleles are lost, this is referred to as which of these?

Possible Answers:

Natural selection

Divergence

Genetic drift

The Founder Effect

Bottlenecking

Correct answer:

Bottlenecking

Explanation:

When a population is reduced for a short period of time, only the rarest alleles are usually lost, as is seen in bottlenecking. In order for a significant change in allelic frequency to be seen, the population must become significantly small, and it must stay small for a significant amount of time. The latter is referred to as the Founder Effect.

Example Question #41 : Population Genetics

A population of geese migrates from Canada to Florida every winter. Individuals from the Canadian population sometimes breed with native Floridian geese. What is this an example of?

Possible Answers:

A prezygotic barrier

Gene flow

Sympatric speciation

Genetic drift

Correct answer:

Gene flow

Explanation:

This is an example of gene flow, because a small number of individuals from one population are passing some genes on to those in another population. Genetic drift occurs within a single population, so it does not apply here. This is not an example of speciation. There can't be a prezygotic barrier present if the geese are able to successfully mate.

Example Question #42 : Population Genetics

For natural selection to occur, which of the following must be true of a population?

Possible Answers:

Phenotypic variations must be based on genetic variations 

Food is not available

Having many populations in one area

The population must be isolated

Must be capable of sexual reproduction

Correct answer:

Phenotypic variations must be based on genetic variations 

Explanation:
Natural selection is one of the basic mechanisms of evolution, along with mutation, migration, and genetic drift. Phenotypic variations must be based on genetic variations rather than on varying environmental conditions to be considered an aspect of natural selection. While sexual reproduction is a medium through which genetic variation increases, it is not a requirement for natural selection to occur (i.e. an antibiotic-resistant strain of bacteria survives despite administration of antibiotics then reproduces via binary fission, increasing the proportion of bacteria in a population who contain the antibiotic resistance genes). Similarly, while both interspecies and intraspecies competition for resources such as food, water, and space may drive natural selection, these processes are not required for it to occur. 

Example Question #302 : Evolution And Genetics

Which type of isolation between populations is due to barriers related to time, such as differences in mating periods or differences in the time of day that individuals are most active.

Possible Answers:

Reproductive isolation

Two of these

Geographic isolation

Temporal isolation

Behavioral isolation

Correct answer:

Temporal isolation

Explanation:

Temporal isolation is between populations due to barriers related to time, such as differences in mating periods or differences in the time of day that individuals are most active. Geographic isolation between populations is due to physical barriers, not time. It wouldn't be both of them because only temporal isolation deals with time, versus geographic isolation is based on the physical barrier between populations such as mountains, rivers, or, for example, insects living on different trees in the jungle. Reproductive isolation is the inability to interbreed between species for various reasons like sterile offspring, physical incompatibility, or different mating rituals.

Example Question #303 : Evolution And Genetics

Which of the following is an example of genetic drift?

Possible Answers:

An organism is born with traits not attributed to the alleles of its parents, but a brand new allele.

An allele increases in frequency due to the increase in fitness it provides the organism.

All of these are examples of genetic drift.

Individuals from one population move and mate with members of a different population.

A massive storm randomly kills many individuals in a population, changing the frequency of alleles in that population.

Correct answer:

A massive storm randomly kills many individuals in a population, changing the frequency of alleles in that population.

Explanation:

Genetic drift occurs when the frequency of alleles in a population change by random chance. Change in allele frequency based on biological fitness is natural selection, not genetic drift. The change in allele frequency due to members moving from one population to another describes migration. A brand new allele that did not exist in the parents is the result of mutation.

Example Question #41 : Population Genetics

A population of wolves is living in an area when a tornado strikes and kills most of the wolves. The population of the wolves has been greatly reduced. Which of the following best describes the impact of the disaster on the genetic makeup of the population of wolves?

Possible Answers:

Hardy-Weinberg principle

Cannot be determined from the information

Bottleneck effect

Founder effect

Gene flow

Correct answer:

Bottleneck effect

Explanation:

The Bottleneck effect happens when an event occurs that drastically reduces the population of a species. The remaining individuals most likely do not represent the genetics of the population before the catastrophic event, since it becomes a much smaller sample size. 

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