AP Biology Practice Quiz: Biodiversity

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

Test your understanding with short quizzes. This quiz has 14 questions to check your progress.

Question 1 of 14

Which of the following best describes the relationship between ecosystem diversity and its resilience to environmental changes, according to the provided text?

A)Higher ecosystem diversity generally leads to lower resilience.B)Higher ecosystem diversity generally leads to higher resilience.C)Ecosystem diversity is unrelated to its resilience.D)Only the number of producers determines an ecosystem's resilience.

All Questions (14)

Which of the following best describes the relationship between ecosystem diversity and its resilience to environmental changes, according to the provided text?

A) Higher ecosystem diversity generally leads to lower resilience.

B) Higher ecosystem diversity generally leads to higher resilience.

C) Ecosystem diversity is unrelated to its resilience.

D) Only the number of producers determines an ecosystem's resilience.

Correct Answer: B

The provided content explicitly states that greater ecosystem diversity contributes to greater resilience against environmental changes. Conversely, it notes that ecosystems with less diversity are often less resilient.

A remote island ecosystem has only three species of plants, one primary herbivore, and one predator. Based on the provided information, how would this ecosystem likely respond to the introduction of a new disease that affects one of the plant species?

A) It would be highly resilient due to its simple structure.

B) It would be less resilient because it has fewer components and less diversity.

C) It would be unaffected as long as the predator species remains healthy.

D) It would gain resilience by adding a new component (the disease) to the ecosystem.

Correct Answer: B

The content states, 'Ecosystems with fewer components and less diversity are often less resilient to environmental changes.' This island ecosystem has very low diversity, making it vulnerable to a change like a new disease.

Which of the following best defines a keystone species?

A) A species that is the most abundant primary producer in an ecosystem.

B) A species that has a disproportionately large effect on its ecosystem relative to its abundance.

C) Any non-native species that is introduced into an ecosystem.

D) The top predator in an ecosystem with the largest biomass.

Correct Answer: B

The text provides a direct definition: 'Keystone species have a disproportionately large effect on their ecosystem relative to their abundance.' This distinguishes them from species that are simply numerous or at the top of the food chain.

According to the text, what is the most likely long-term consequence of removing a keystone species from an ecosystem?

A) A temporary decrease in the population of primary producers.

B) An increase in the overall resilience of the ecosystem.

C) The ecosystem may collapse.

D) Another species will quickly and seamlessly fill its niche.

Correct Answer: C

The content explicitly states that the removal of a keystone species 'often leads to ecosystem collapse.' This highlights their critical role in maintaining the ecosystem's structure and function.

A wildfire burns through a large section of a forest, destroying a significant portion of the undergrowth but leaving the largest trees intact. Based on the provided text, what is the most likely immediate effect on the ecosystem's structure?

A) There will be no change to the ecosystem's structure because the producers (large trees) remain.

B) The ecosystem's short-term structure will be altered due to the removal of biotic components.

C) The ecosystem's resilience will permanently increase.

D) Only the abiotic factors, such as soil composition, will be affected.

Correct Answer: B

The text states, 'the addition or removal of any component of an ecosystem will affect its overall short-term and long-term structure.' The fire removed biotic components (the undergrowth), which will cause a short-term structural change.

Which of the following are all identified in the text as being critical for maintaining ecosystem diversity?

A) Apex predators, decomposers, and soil.

B) Sunlight, water, and consumers.

C) Keystone species, producers, and essential abiotic factors.

D) Herbivores, carnivores, and omnivores.

Correct Answer: C

The text specifically lists these three categories: 'Keystone species, producers, and essential abiotic and biotic factors are critical for maintaining ecosystem diversity.' Option C is the only one that correctly identifies components from this list.

In a coastal ecosystem, sea otters prey on sea urchins, which in turn graze on kelp. The otters are not abundant, but without them, the urchin population explodes and destroys the kelp forests, which are the primary producers for many other species. This scenario is a direct example of:

A) An ecosystem with low diversity being highly resilient.

B) The critical role of a keystone species in maintaining ecosystem structure.

C) An abiotic factor being removed from an ecosystem.

D) The removal of a producer leading to increased overall diversity.

Correct Answer: B

The sea otter has a large effect on the ecosystem despite its low numbers, fitting the definition of a keystone species. Its removal leads to a cascade of negative effects, demonstrating its critical role as described in the text.

A farmer decides to convert a diverse meadow into a monoculture soybean field. According to the principles described, this action will most likely have what effect on the ecosystem's resilience to pests and drought?

A) It will increase resilience because the system is now simpler to manage.

B) It will have no effect on resilience, as the amount of producer biomass is the same.

C) It will decrease resilience because the ecosystem has fewer components and less diversity.

D) It will increase resilience because soybeans are a hardy producer.

Correct Answer: C

The conversion from a diverse meadow to a monoculture field is a drastic reduction in ecosystem diversity. The text states that 'Ecosystems with fewer components and less diversity are often less resilient to environmental changes' like pests or drought.

The damming of a river prevents seasonal flooding that historically deposited nutrient-rich silt onto the surrounding floodplain. This change represents the alteration of what critical component for maintaining ecosystem diversity?

A) A keystone species.

B) A primary producer.

C) An essential abiotic factor.

D) A biotic component.

Correct Answer: C

The seasonal flooding and silt deposition are non-living (abiotic) processes that are essential for the health of the floodplain ecosystem. The text identifies 'essential abiotic...factors' as critical for maintaining diversity.

An ecosystem experiences a significant, negative change in its overall structure after a single, low-abundance species of fungus is eliminated by a chemical spill. Which of the following is the most likely explanation for this drastic change?

A) The fungus was the main producer for the entire ecosystem.

B) The fungus was likely a keystone species, having a disproportionately large effect on the ecosystem.

C) Ecosystems with fewer components are always more stable, so this outcome is unexpected.

D) The removal of any species always results in a complete and permanent collapse of the ecosystem.

Correct Answer: B

The key information is that a 'low-abundance' species caused a 'significant, negative change' upon its removal. This perfectly aligns with the definition of a keystone species having a 'disproportionately large effect on their ecosystem relative to their abundance.'

If a new, highly efficient predator is introduced into an ecosystem and begins to hunt multiple native prey species, what does the provided text suggest about the potential long-term impact?

A) The ecosystem's structure will not be affected in the long term.

B) The addition of this new component will affect the ecosystem's overall structure.

C) The ecosystem's resilience will automatically increase to cope with the new predator.

D) Only the abiotic factors of the ecosystem will be altered.

Correct Answer: B

The text states that 'the addition or removal of any component of an ecosystem will affect its overall short-term and long-term structure.' The introduction of a new predator is the addition of a significant biotic component.

How does the role of a primary producer, like a widespread species of grass, differ from the role of a keystone species, like a prairie dog, in maintaining ecosystem diversity?

A) The producer is an abiotic factor, while the keystone species is a biotic factor.

B) The producer's importance is based on its large biomass and energy provision, while the keystone species' importance is disproportionately large compared to its biomass.

C) The removal of the producer has no effect, while the removal of the keystone species causes collapse.

D) The keystone species is always the most abundant, while the producer is less abundant.

Correct Answer: B

Producers are critical due to their foundational role in the food web (often high abundance/biomass). The text defines keystone species by their disproportionately large effect relative to their (often low) abundance. This question requires distinguishing between two different types of critical components.

A student argues that an ecosystem with only a few, highly-specialized species is stronger because there is less competition. Why is this argument incorrect according to the provided text?

A) The argument is correct; less diversity means less competition and greater stability.

B) The argument is incorrect because such an ecosystem is less resilient to environmental changes.

C) The argument is incorrect because keystone species are only found in low-diversity ecosystems.

D) The argument is correct because the removal of one component would have a minimal effect.

Correct Answer: B

The text directly contradicts the student's argument by stating, 'Ecosystems with fewer components and less diversity are often less resilient to environmental changes.' The lack of diversity makes the ecosystem more vulnerable, not stronger.

Which of the following scenarios best illustrates the concept that higher ecosystem diversity leads to higher resilience?

A) A monoculture crop fails completely when a single pest is introduced.

B) A coral reef with hundreds of species experiences bleaching in some corals due to a heatwave but the overall ecosystem structure persists.

C) The removal of a single predator species from a simple food web causes the entire system to collapse.

D) A parking lot remains barren and devoid of life years after being abandoned.

Correct Answer: B

This scenario shows a highly diverse ecosystem (coral reef) facing a significant environmental change (heatwave). While some components are damaged, the overall structure persists, demonstrating resilience. The other options illustrate low resilience (A, C) or a lack of an ecosystem (D).