AP Biology: Source-Sink Dynamics Practice Questions
Practice source-sink dynamics with original AP Biology multiple-choice questions. These items focus on high-quality source habitats, low-quality sink habitats, dispersal, population growth rates, and how habitat connections affect regional persistence.
Free original practice questions for study purposes. Open Exam Prep is an independent study resource and is not affiliated with, endorsed by, or sponsored by the makers of AP Exams.
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Answer the questions below — you get instant feedback and a full explanation for each.
1. In population ecology, what best describes a source habitat?
Explanation. A source habitat has positive local population growth. It can produce more individuals than it loses, allowing some individuals to disperse to other patches.
2. Which statement best describes a sink habitat?
Explanation. A sink habitat has negative local population growth. Without immigration from source habitats, the local population would decline or disappear.
3. A bird population in a forest patch produces more fledglings than are needed to replace adult deaths. Some juveniles move to nearby patches. Which label best fits the forest patch?
Explanation. The forest patch is a source because local reproduction exceeds mortality and it can export dispersing juveniles to other patches.
4. A roadside grassland has a butterfly population that produces too few offspring to offset adult mortality, but adults arrive each year from a nearby preserve. What is the best interpretation?
Explanation. The roadside patch has negative local growth, but immigration keeps it occupied. That pattern is characteristic of a sink habitat.
5. Which data would most directly help classify a habitat patch as a source or sink?
Explanation. Source-sink classification depends on whether local reproduction balances mortality and whether movement among patches changes local abundance.
6. Why can a sink habitat still contain many individuals during a census?
Explanation. A sink can appear occupied or even crowded if immigrants arrive often enough. Census size alone does not prove that the habitat is self-sustaining.
7. A conservation biologist protects only a visible sink patch while the nearby source patch is developed. What outcome is most likely over time?
Explanation. If a sink depends on immigrants from a source, losing the source can reduce regional persistence even if the sink patch itself remains protected.
8. Which scenario best illustrates source-sink dynamics rather than simple isolated population growth?
Explanation. Source-sink dynamics require differences in patch quality and movement among patches. The sink can remain occupied because individuals arrive from a source.
9. In a source-sink system, what is one possible effect of building a wildlife corridor from a high-quality source patch to a low-quality sink patch?
Explanation. A corridor can increase movement among patches. In a source-sink system, that movement may help keep a sink occupied, though local habitat quality still matters.
10. A patch has lambda greater than 1 when immigration and emigration are excluded. What does this suggest about the patch?
Explanation. Lambda greater than 1 indicates positive local growth. If that pattern is due to local births exceeding deaths, the patch can function as a source.
11. Why is it risky to identify sources and sinks using population density alone?
Explanation. Density is a snapshot. Source-sink status depends on demographic rates and movement, so a high-density patch can still be a sink if immigrants maintain it.
12. Which management action best follows from source-sink theory?
Explanation. Effective management should consider which patches produce surplus individuals and how dispersal connects the landscape, not just whether a patch is occupied.
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FAQ
What are source-sink dynamics in AP Biology?
Source-sink dynamics describe connected habitat patches where high-quality source patches produce surplus individuals and low-quality sink patches may persist because immigrants arrive.
How can you tell a source from a sink?
Look at local birth rates, death rates, immigration, and emigration. A source has positive local growth, while a sink has negative local growth without immigration.
Why does source-sink ecology matter for conservation?
Protecting only occupied sink patches can miss the productive source habitats that support the regional population through dispersal.