AP Biology: Soil Seed Bank Persistence and Recruitment Practice Questions
Practice ecological reasoning with original AP Biology multiple-choice questions about how viable seeds enter, persist in, and leave soil seed banks. These items connect dormancy and disturbance to seedling recruitment while separating seed abundance, viability, germination, establishment, and causal evidence.
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 distinguishes a persistent soil seed bank from a transient soil seed bank?
Explanation. Persistence refers to viable seeds remaining in the soil across seasons or years. A transient bank may contain viable seeds, but most germinate or die before persisting into later seasons.
2. Researchers recover 500 seeds from equal soil volumes at each of two sites. Which additional result is most necessary before concluding that the sites contain equally large viable seed banks?
Explanation. Counting intact seeds does not show how many remain alive. Viability tests are needed to compare the living portion of each seed bank rather than combining viable and dead seeds.
3. Which study best separates seedlings emerging from the existing soil seed bank from seedlings produced by new seed rain?
Explanation. Seed-rain exclusion limits newly arriving seeds while matched controls reveal background emergence. Keeping light and water comparable reduces alternative explanations for differences between treatments.
4. After a controlled soil disturbance, many seedlings emerge from plots that received no new seeds. What is the most cautious conclusion?
Explanation. Excluding new seeds supports the existing bank as the source of emergence. Emergence alone does not establish seed age, later survival, reproduction, or a universal benefit of disturbance.
5. Why can a persistent seed bank reduce a population's risk in a variable environment?
Explanation. Seeds that remain viable and germinate in different years provide temporal risk spreading. Persistence does not guarantee germination or survival and does not remove normal evolutionary or resource constraints.
6. A soil core contains many viable seeds, but few seedlings establish after germination. Which process most directly explains the gap?
Explanation. Recruitment requires more than a viable seed and germination. Competition, herbivory, drought, pathogens, or unsuitable microsites can kill germinants before they become established seedlings.
7. Scientists want to test whether alternating temperatures break dormancy in a seed bank species. Which design provides the strongest causal evidence?
Explanation. Random assignment and controlled conditions isolate the temperature regime as the tested variable. A matched constant-temperature group provides the comparison needed for a causal inference.
8. Seeds buried in mesh bags show 70% viability after three years, while unburied seeds kept in a dry laboratory show 90% viability. Which inference is best supported?
Explanation. The percentages show an association between treatment environments and viability. A strong causal claim requires comparable initial seeds, replication, and control of factors such as moisture, temperature, pathogens, and retrieval damage.
9. How can a soil seed bank contribute to vegetation recovery after a disturbance removes adult plants?
Explanation. A viable seed bank can provide local propagules after adult loss. Recovery still depends on germination cues, microsites, competition, survival, and whether the pre-disturbance species are represented in the bank.
10. A species is abundant as adults but nearly absent from soil seed-bank samples. Which explanation is most consistent with the observation?
Explanation. Some species form mainly transient seed banks, so adult abundance need not match persistent seed abundance. Other explanations remain possible, but short seed longevity directly fits the pattern.
11. Which measurement best estimates successful recruitment rather than seed-bank size or initial germination alone?
Explanation. Recruitment describes entry into an established population stage. Tracking new individuals through a defined survival threshold measures that outcome more directly than seed counts, viability, imbibition, or germination alone.
12. A field survey finds that plots with deeper litter have fewer emerging seedlings and more viable seeds remaining in the soil. What is the strongest conclusion from this survey alone?
Explanation. The survey reveals a pattern but does not rule out correlated differences such as moisture, canopy cover, seed input, or species composition. Manipulating litter with replication would better test causation.
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FAQ
What is a soil seed bank?
A soil seed bank is the pool of viable, ungerminated seeds present on or within the soil. It changes as seeds arrive, germinate, die, are eaten, or move through the soil.
Does a large seed bank guarantee strong plant recruitment?
No. Seeds must remain viable, receive appropriate germination cues, and survive post-germination bottlenecks such as drought, competition, herbivory, and unsuitable microsites.
How do ecologists test whether a seed bank aids recovery?
They may combine soil-core germination or viability assays with seed-rain controls, disturbance treatments, field emergence monitoring, and later seedling-survival measurements.