AP Biology: Seed Dispersal Distance and Recruitment Practice Questions
Practice ecological reasoning with original AP Biology multiple-choice questions about how seed dispersal distance relates to plant recruitment. These questions separate seed arrival from establishment, connect seed shadows to later seedling survival, and emphasize experimental evidence before making causal claims.
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. What is the clearest distinction between seed dispersal and seedling recruitment?
Explanation. Dispersal determines where seeds arrive, while recruitment depends on later transitions such as germination and survival to a specified seedling stage. Arrival alone does not demonstrate establishment.
2. Which field design most directly tests how distance from a parent plant affects per-seed recruitment?
Explanation. Equal seed additions and replicated distance treatments separate per-seed recruitment from the natural decline in seed number with distance. Tracking the same establishment stage makes the outcomes comparable.
3. Seed density declines with distance from a parent tree, but survival probability per seed rises over the same range. Which recruitment pattern is possible?
Explanation. Recruitment reflects both the number of seeds arriving and their probability of surviving. Opposing trends in arrival and survival can produce an intermediate peak rather than a strictly increasing or decreasing pattern.
4. An observational survey finds higher seedling survival farther from adult conspecifics. What is the most cautious interpretation?
Explanation. Distance may covary with seedling density, light, moisture, soil conditions, and enemy exposure. The survey reveals a pattern but does not isolate distance as the sole cause.
5. What potential population-level benefit can rare long-distance dispersal provide?
Explanation. Even if uncommon, long-distance events can move propagules beyond the local population into suitable sites. Successful colonization still depends on seed viability, habitat quality, and establishment.
6. In plant ecology, what does a seed shadow describe?
Explanation. A seed shadow represents where seeds are deposited relative to their source. It is an input to recruitment patterns, not a direct measure of later survival.
7. A species is absent from apparently suitable plots far from adult plants. Which result best supports seed limitation?
Explanation. If seed addition raises recruitment in otherwise comparable distant plots, natural seed arrival was limiting at least part of the recruitment process. Unseeded controls show the background recruitment rate.
8. Why can a simple comparison of near-parent and far-parent seedlings confuse distance effects with density effects?
Explanation. Natural seed fall often creates high conspecific density close to the source. A factorial design that varies distance and density independently provides stronger evidence about their separate effects.
9. Which outcome most directly measures recruitment rather than dispersal distance alone?
Explanation. Recruitment is a demographic transition, so the useful measure links deposited seeds to survival through a stated establishment stage. A distance measurement alone describes movement, not successful establishment.
10. Two dispersers move equal numbers of viable seeds the same average distance, but one produces more recruits. Which explanation is most plausible?
Explanation. Dispersal quality depends on deposition context as well as distance. Different microsites can change post-dispersal survival even when seed number, viability, and average distance are similar.
11. Which method best connects a measured dispersal distance to later recruitment?
Explanation. Individual tags or genetic assignment can connect a seed to its source and deposition distance. Repeated monitoring then links that movement record to germination and survival.
12. Which statement best evaluates the claim that greater dispersal distance always increases plant recruitment?
Explanation. Moving farther may reduce some near-parent risks but can also place seeds in unsuitable habitat, and fewer seeds may reach long distances. The net recruitment pattern must be measured for the species and setting.
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FAQ
Does the farthest-dispersed seed necessarily have the highest recruitment probability?
No. Distance can change density and enemy exposure, but habitat quality and post-dispersal survival also matter. Recruitment may increase, decrease, or peak at an intermediate distance.
Why is seed arrival not enough to demonstrate recruitment?
A deposited seed may be nonviable, consumed, fail to germinate, or die as a seedling. Recruitment requires survival to a clearly defined establishment stage.
How can an experiment separate distance from seed density?
Researchers can place equal numbers of viable seeds in replicated plots at multiple distances, or independently vary both distance and density. Standardized treatments and later survival measurements help isolate each factor.