AP Biology: Predator-Prey Population Cycles Practice Questions
Practice predator-prey population cycles with original AP Biology multiple-choice questions. These items connect changes in prey abundance to delayed predator responses, population graphs, model assumptions, trophic cascades, and experimental evidence.
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1. In a repeating predator-prey cycle, why does the predator population often peak after the prey population?
Explanation. Greater prey availability can support more predator survival and reproduction. Those demographic changes take time, so the predator peak commonly follows the prey peak.
2. A graph shows prey abundance rising first, followed by predator abundance. What change is most likely to occur next in a basic predator-prey cycle?
Explanation. As predator numbers rise, total predation pressure can increase. This can help drive prey abundance downward in the next phase of the cycle.
3. After a prey population declines sharply, what most directly explains a later decline in its specialist predator population?
Explanation. A specialist predator depends strongly on its prey. When prey become scarce, food limitation can reduce predator survival and reproduction after a delay.
4. Researchers compare two otherwise similar islands. Predators are removed from one island, while the other remains unchanged. Which initial result best supports the hypothesis that predators limit prey abundance?
Explanation. A larger prey increase after predator removal, compared with an unchanged control island, supports the idea that predation had limited prey abundance.
5. Which event is most likely to disrupt a predator-prey cycle through a density-independent effect?
Explanation. A severe wildfire can affect populations regardless of their density. The other choices become stronger or more frequent as population density changes.
6. On an unlabeled graph of a coupled predator-prey cycle, curve X consistently peaks shortly before curve Y. If the interaction is the main cause of the pattern, which identification is most reasonable?
Explanation. Prey abundance commonly increases first, providing food that supports a delayed increase in the predator population. Thus the earlier-peaking curve is reasonably identified as prey.
7. Which pair of assumptions belongs to the simplest Lotka-Volterra predator-prey model?
Explanation. The basic model treats prey as capable of growth without predators and treats predator persistence as dependent on consuming prey. Real ecosystems add many further limits and interactions.
8. A field study finds that predator and prey numbers oscillate over several years. Why does this observation alone not prove that predation caused the oscillation?
Explanation. A correlated pattern is evidence of association, not proof of causation. Weather, resources, disease, competitors, and other factors could contribute to both population changes.
9. Which study design would best test whether prey refuges change the amplitude of predator-prey cycles?
Explanation. Replication, a refuge treatment, a comparable control, and repeated measurements of both populations allow researchers to test how refuges affect cycle amplitude.
10. A predator suppresses an herbivore, allowing plant biomass to increase. This indirect effect is an example of what ecological pattern?
Explanation. The predator indirectly benefits plants by reducing herbivore pressure. That chain of effects across trophic levels is a trophic cascade.
11. What does a predator's functional response describe?
Explanation. A functional response links prey density to the consumption rate of an individual predator. It differs from a numerical response, which concerns changes in predator abundance.
12. A prey species gains access to narrow shelters that its predator cannot enter. Which immediate mechanism could alter the population cycle?
Explanation. A refuge can lower encounter or capture rates. That change can weaken predation pressure and alter the timing or amplitude of population fluctuations.
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FAQ
Why do predator populations usually peak after prey populations?
An increase in prey provides more food, but predator survival, reproduction, and maturation take time. This creates a delayed predator response.
Do all predator-prey populations show regular cycles?
No. Alternative prey, refuges, weather, disease, competition, migration, and resource limits can weaken, reshape, or obscure cycles.
How should I interpret predator-prey graphs on AP Biology questions?
Compare the timing of peaks and declines, look for a predator lag after prey growth, and use the experimental context before assigning cause.