AP Biology Practice Quiz: Disruptions in Ecosystems

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 16 questions to check your progress.

Question 1 of 16

A population of insects is repeatedly sprayed with a specific insecticide. Over several generations, the insect population shows increasing resistance to the insecticide. Which of the following best explains this observation based on the provided principles?

A)The insecticide caused a directed mutation in the insects, making them resistant.B)Individual insects learned to tolerate the insecticide and passed this trait to their offspring.C)Random, preexisting variations in the insect population included some resistant individuals who survived and reproduced.D)The insecticide was a meteorological event that altered the insects' habitat.

All Questions (16)

A) The insecticide caused a directed mutation in the insects, making them resistant.

B) Individual insects learned to tolerate the insecticide and passed this trait to their offspring.

C) Random, preexisting variations in the insect population included some resistant individuals who survived and reproduced.

D) The insecticide was a meteorological event that altered the insects' habitat.

Correct Answer: C

According to the content, mutations are random and not directed by environmental pressures (Content 7). The environment (the insecticide) selects for preexisting genetic variations that provide an advantage (Content 1, 5). Therefore, some insects already had the resistance trait due to random variation, and they were the ones to survive and pass it on.

Zebra mussels, a non-native species, were introduced into the Great Lakes. They filter vast amounts of phytoplankton from the water and their shells cover surfaces, displacing native species. This is a clear example of how an invasive species can disrupt an ecosystem by:

A) Causing a major geological event.

B) Introducing a heterozygote advantage to native species.

C) Outcompeting native species and exploiting a new niche.

D) Leading to eutrophication through pollution.

Correct Answer: C

The content states that invasive species can disrupt ecosystems as they exploit new niches and outcompete native species (Content 2, 8). The zebra mussels are outcompeting native filter feeders for phytoplankton and displacing them for space.

Runoff from an agricultural area introduces high levels of nitrates and phosphates into a nearby pond, leading to a massive algal bloom. The subsequent decomposition of the algae depletes the oxygen in the water, causing a fish kill. This entire process is best described as:

A) Biomagnification

B) Eutrophication

C) Heterozygote advantage

D) A meteorological disruption

Correct Answer: B

Content 9 describes eutrophication as a human impact, often caused by pollution (like fertilizer runoff), that can accelerate ecosystem changes. The scenario of nutrient enrichment leading to algal blooms and oxygen depletion is the classic definition of eutrophication.

A massive forest fire, started by a lightning strike, burns through a large national park, clearing vast areas of trees and changing the landscape. This event is an example of a change in ecosystem structure caused by:

A) An invasive species.

B) A human activity.

C) A meteorological activity.

D) A random genetic mutation.

Correct Answer: C

Content 4 and 10 explain that geological and meteorological activities lead to changes in ecosystem structure and dynamics. A lightning-caused forest fire is a meteorological event that affects habitat and the ecosystem.

In certain regions of Africa, individuals who are heterozygous for the sickle-cell allele (AS) have a survival advantage in malaria-prone environments compared to homozygous dominant (AA) and homozygous recessive (SS) individuals. This phenomenon is known as:

A) An adaptation favored by selection

B) A random mutation

C) Biomagnification

D) Heterozygote advantage

Correct Answer: D

This scenario directly matches the definition provided in Content 6: 'Heterozygote advantage occurs when the heterozygous genotype has higher relative fitness than either homozygous genotype.'

A factory releases a small amount of a persistent, fat-soluble toxin into a lake. The toxin is found in very low concentrations in the water but at much higher concentrations in the tissues of ospreys that eat fish from the lake. This increase in concentration up the food chain is an example of:

A) Eutrophication

B) The introduction of an invasive species

C) Biomagnification

D) A geological ecosystem disruption

Correct Answer: C

Content 9 identifies biomagnification as a consequence of human pollution. It is the process by which the concentration of a toxin increases in organisms at successively higher levels in a food chain, as described in the question.

The kudzu vine was introduced to the United States from Asia to control soil erosion. It grows extremely fast and has no natural herbivores in its new environment, allowing it to smother and kill native trees and shrubs. The success of kudzu as an invasive species is best explained by its:

A) High rate of random mutation.

B) Lack of natural predators.

C) Ability to cause eutrophication.

D) Benefit from geological activity.

Correct Answer: B

Content 8 explicitly states that a reason for the success of invasive species is that they may 'lack natural predators' (or herbivores, in the case of a plant). This allows their populations to grow unchecked.

A genetic variation in a species of moth that provides better camouflage on tree bark is an example of:

A) An adaptation

B) An invasive species

C) A human activity

D) A meteorological event

Correct Answer: A

According to Content 5, an adaptation is a genetic variation that is favored by selection because it provides an advantage in a specific environment. Better camouflage is a classic example of such an adaptation.

Which of the following statements accurately describes the role of mutations in evolution within the context of environmental pressure?

A) Mutations are caused by environmental pressures to create beneficial adaptations.

B) Mutations occur randomly, and environmental pressures may favor certain variations.

C) Human activities are the primary cause of all new mutations in a population.

D) Geological events direct mutations to help species survive habitat changes.

Correct Answer: B

This synthesizes information from multiple points. Content 7 states that mutations are random and not directed by specific environmental pressures. Content 1 explains that the environment interacts with these random or preexisting variations, and Content 5 defines an adaptation as a variation favored by selection.

The formation of a mountain range due to tectonic plate collision separates a population of plants into two isolated groups, leading to changes in the distribution of the ecosystem. This is a direct result of:

A) A major geological event.

B) An invasive species introduction.

C) Human-caused pollution.

D) A short-term meteorological event.

Correct Answer: A

Content 10 states that major geological events affect the distribution of ecosystems over time. The formation of a mountain range is a major geological event that alters habitats and can isolate populations.

Which of the following is explicitly mentioned in the text as a human activity that leads to changes in ecosystem structure and dynamics?

A) Volcanic eruptions

B) Pollution

C) Random mutations

D) Heterozygote advantage

Correct Answer: B

Content 3 and 9 directly name human activities, such as pollution, as drivers of change in ecosystem structure and dynamics. The other options are natural phenomena or genetic principles.

A scientist observes that an invasive grass species is spreading rapidly in a prairie, displacing native grasses. Which of the following is the LEAST likely direct explanation for the invasive species' success based on the provided content?

A) The invasive grass is exploiting a niche not used by native plants.

B) The invasive grass is outcompeting native grasses for water and nutrients.

C) The invasive grass lacks the natural herbivores that controlled it in its original habitat.

D) The invasive grass is experiencing a heterozygote advantage over the native grasses.

Correct Answer: D

Content 8 provides A, B, and C as common reasons for the success of invasive species. While heterozygote advantage (Content 6) is a valid genetic principle that confers fitness, it is a specific mechanism within a population's gene pool and is not presented as a general explanation for why a species becomes invasive in a new environment.

A hurricane makes landfall, causing massive coastal erosion and flooding saltwater into freshwater marshes, killing many salt-intolerant plant species. This event directly illustrates how:

A) Human pollution can lead to biomagnification.

B) Invasive species can outcompete native species.

C) Meteorological events can affect habitat change.

D) Random mutations are favored by selection.

Correct Answer: C

A hurricane is a major meteorological event. According to Content 4 and 10, such events are a primary cause of habitat change and alterations to ecosystem structure and dynamics.

The provided content suggests that human impacts on ecosystems can ultimately lead to which severe outcome for affected species?

A) An increase in the rate of beneficial mutations.

B) The establishment of heterozygote advantage.

C) The acceleration of changes that can drive extinctions.

D) The reversal of long-term geological changes.

Correct Answer: C

Content 9 explicitly states that human impacts, such as pollution, 'can accelerate ecosystem changes and drive extinctions.'

A remote island ecosystem is stable for thousands of years. A new volcanic vent opens on the seafloor nearby, slowly changing the ocean acidity around the island. Which statement best describes the likely response of the island's marine populations?

A) The change in acidity will cause all species to develop new, favorable mutations to survive.

B) The environmental change will act upon preexisting genetic variations, favoring individuals who can tolerate higher acidity.

C) The geological event will have no effect on the populations because they are already adapted.

D) All marine populations will be outcompeted by invasive species better suited to the new acidity.

Correct Answer: B

This question combines the concepts of a geological event (Content 10) causing an environmental change that then interacts with population variation (Content 1). The change in the environment does not cause mutations (Content 7), but rather selects from the random variations that are already present in the populations.

Which of the following correctly pairs a type of ecosystem disruption with its cause?

A) Invasive Species :: A random mutation in a native population

B) Geological Activity :: Pollution from a factory

C) Human Activity :: Eutrophication from fertilizer runoff

D) Meteorological Activity :: Introduction of a non-native predator

Correct Answer: C

Content 3 and 9 link human activities to changes like eutrophication. Fertilizer runoff is a human-caused form of pollution. The other options are mismatched; for example, pollution is a human activity, not a geological one, and introducing a predator is not a meteorological event.