AP Biology: Seed Coat Hardness and Disperser Handling Practice Questions
Practice ecological and evolutionary reasoning with original AP Biology multiple-choice questions about how seed coat traits interact with animal feeding and dispersal behavior. These items distinguish fruit or seed removal from effective dispersal, identify trade-offs between protection and germination, and test the evidence needed for 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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Answer the questions below — you get instant feedback and a full explanation for each.
1. A plant population produces seeds with unusually hard coats. Which direct benefit is most likely before germination?
Explanation. A hard seed coat can protect the embryo while the seed is dormant or being handled. It does not guarantee dispersal or remove the environmental requirements for germination.
2. Seeds of one species germinate more often after passing intact through a bird's digestive tract. Which mechanism best explains the result?
Explanation. Mechanical or chemical scarification during gut passage can weaken a resistant coat and improve imbibition after deposition. The effect varies among plant and animal species.
3. Two rodents collect equal numbers of hard-coated seeds. Rodent A swallows and destroys most embryos, while rodent B caches many intact seeds and fails to recover some. Which measurement best distinguishes their effects on plant recruitment?
Explanation. Initial removal does not reveal whether handling produces seed predation or dispersal. Following viability, germination, and establishment measures the ecological outcome of each interaction.
4. A field survey finds that harder seeds are more often carried by large-billed birds. What is the most cautious conclusion?
Explanation. An observational association supports a trait-matching hypothesis but does not isolate a mechanism. Direct measurements and controls are needed to separate hardness from correlated traits and ecological opportunity.
5. A seed coat becomes so resistant that water rarely enters even after the seed reaches suitable soil. Which trade-off is most evident?
Explanation. Increased hardness can protect seeds, but excessive resistance may maintain dormancy by limiting water uptake. The fitness effect depends on whether later scarification or weathering opens the coat at an advantageous time.
6. Which animal trait most directly affects whether a hard-coated seed is cracked, swallowed intact, or rejected?
Explanation. Feeding structures and force directly interact with coat resistance. These traits can determine whether handling destroys the embryo, leaves the seed intact, or prevents consumption.
7. Researchers want to test whether moderate abrasion by a disperser improves germination without reducing seed viability. Which experiment is strongest?
Explanation. A controlled abrasion gradient links treatment intensity to permeability, viability, and germination. Measuring all three outcomes reveals both the potential benefit and the damage threshold.
8. Hard-coated seeds survive passage through one bird species but are crushed by another species before swallowing. Which statement best explains the difference?
Explanation. The same seed trait can lead to different outcomes because animals differ in feeding structures, forces, and behaviors. Ecological function belongs to the interaction, not to one trait in isolation.
9. A rodent caches hard-coated seeds in many shallow sites, and some caches are forgotten. Which immediate dispersal benefit can result?
Explanation. Forgotten caches can provide directed movement and burial while leaving seeds intact. The benefit is conditional because rodents may recover seeds and cache sites differ in suitability.
10. After a hard-seed-cracking bird declines, softer-billed birds remove more fruits but spit all intact seeds beneath parent plants. What does this pattern show?
Explanation. New or stronger feeding links represent rewiring, but deposition beneath parents may not replace scarification, transport distance, or deposition quality. Link counts alone can therefore overstate functional recovery.
11. Which response variable best tests whether disperser handling of hard-coated seeds increases effective dispersal?
Explanation. Effective dispersal integrates handling, seed survival, movement, deposition quality, germination, and establishment. A feeding count or single trait measures only part of that pathway.
12. In a dry habitat, hard-coated seeds benefit from scarification after rare heavy rains, but the same coat treatment reduces survival during long dry periods. Which conclusion is best supported?
Explanation. The value of protection versus rapid permeability changes with rainfall timing, damage risk, and deposition conditions. A trait or handling effect that is beneficial in one context can be costly in another.
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FAQ
How can a hard seed coat affect germination?
It can protect the embryo and maintain dormancy, but it may also delay water uptake. Abrasion, digestion, weathering, heat, or other cues can weaken some coats and permit germination.
Does animal handling always help hard-coated seeds?
No. Handling may move, bury, or scarify a seed, but it can also crack the embryo or result in seed predation. The outcome depends on both plant and animal traits.
Why is seed removal not enough to prove effective dispersal?
Researchers must also determine whether seeds remain viable, where they are deposited, whether conditions support germination, and whether seedlings establish.