AP Biology: Frugivore Body Size and Dispersal Function Practice Questions
Practice ecological reasoning with original AP Biology multiple-choice questions about fruit-eating animals and seed dispersal. These items distinguish body-size correlations from mechanisms, fruit removal from effective dispersal, and observational patterns from evidence that supports causal conclusions.
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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1. A tree produces fruits whose seeds are wider than the gape of every small bird in the community. Which frugivores are most likely to swallow the fruits whole and transport the intact seeds?
Explanation. Gape limitation can prevent small frugivores from swallowing large fruits or seeds. Larger-gaped animals may therefore provide a dispersal pathway unavailable to smaller species, although swallowing does not by itself prove successful recruitment.
2. Researchers find that larger fruit-eating mammals usually carry seeds farther than smaller mammals in one forest. Which mechanism most directly could produce this pattern?
Explanation. Movement range combined with the time a seed remains in the digestive tract can influence dispersal distance. The relationship is not universal because behavior, habitat use, gut passage, and fruit traits also matter.
3. Two bird species remove equal numbers of fruits. Species A drops most seeds beneath parent trees, while species B deposits seeds in canopy gaps where seedling survival is high. Which measurement best captures their difference in dispersal quality?
Explanation. Dispersal quality depends on what happens after removal, including seed condition, deposition location, germination, and recruitment. Following seed fate at deposition sites distinguishes the two birds' functional contributions.
4. A survey reports that forests with more large frugivores also have more widely dispersed seedlings. What is the most cautious interpretation?
Explanation. An observational correlation can motivate a causal hypothesis but cannot exclude confounding variables such as forest area, fruit abundance, hunting pressure, or habitat connectivity. Direct tracking or controlled comparisons would strengthen inference.
5. Large-bodied frugivores disappear from a forest where they were the only animals able to swallow a plant's large fruits. Which immediate functional effect is most likely?
Explanation. If gape size makes large frugivores the only effective handlers, their loss removes an important transport pathway. Evolutionary change is not immediate, and replacement depends on whether other animals can perform the same function.
6. A medium-sized bird disperses fewer seeds than a large mammal but deposits a greater fraction of them in safe sites. Which conclusion best compares their functions?
Explanation. Effective dispersal combines quantity and quality. A species moving fewer seeds can still contribute strongly if it delivers a high fraction to sites where seeds survive and establish.
7. Which study would provide the strongest evidence that frugivore body size affects dispersal distance through animal movement?
Explanation. Combining movement paths, retention time, and observed seed deposition directly tests the proposed mechanism linking frugivore traits to dispersal distance. Each measurement connects a step in the causal chain.
8. A community contains several small birds with overlapping diets but only one large-bodied disperser of large-seeded plants. What does this pattern suggest about functional redundancy?
Explanation. Functional redundancy is specific to ecological tasks. Several small birds may overlap in dispersing small seeds while none can replace the large-bodied species for fruits limited by gape or handling capacity.
9. Heavy hunting selectively reduces large frugivores while total fruit production remains similar. Which plant group is predicted to experience the greatest initial dispersal limitation?
Explanation. Trait matching makes large-fruited plants that depend on large animals especially vulnerable to selective loss. Plants with abiotic dispersal or many effective remaining partners are less directly affected.
10. After large mammals decline, rodents remove more fallen fruits but cache most seeds near parent trees. What process and limitation are both represented?
Explanation. The rodents form or strengthen interactions after the decline, which is interaction rewiring. Their short-distance caching may restore fruit removal without replacing the lost long-distance transport function.
11. Researchers want to compare the dispersal effectiveness of three frugivores that differ in body size. Which response variable is most informative?
Explanation. The number of viable seeds delivered to suitable sites and contributing to establishment integrates seed quantity, handling effects, movement, deposition quality, and early recruitment.
12. Across four islands, larger frugivores disperse seeds farther only on islands with continuous forest. Which conclusion is best supported?
Explanation. The differing pattern suggests that landscape structure modifies how body size relates to movement and seed dispersal. Replication and direct movement measurements would help identify the mechanism.
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FAQ
Why can frugivore body size affect seed dispersal?
Body size can correlate with gape width, fruit-handling ability, movement range, and gut-retention time. These traits may influence which fruits an animal can consume and where seeds are deposited.
Are larger frugivores always better seed dispersers?
No. Effectiveness also depends on diet, seed damage, movement behavior, deposition habitat, abundance, interaction frequency, and seedling survival. Smaller species can provide high-quality dispersal in some contexts.
How do scientists measure effective seed dispersal?
They combine the number of seeds moved with seed condition, dispersal distance, deposition-site quality, germination, and recruitment. Fruit removal alone measures only an early step.