AP Biology: Seed Bank Depth, Disturbance, and Emergence Practice Questions
Practice ecological reasoning with original AP Biology multiple-choice questions about how seed depth and disturbance affect emergence. These questions distinguish viable seed abundance from emergence and establishment, and they emphasize controlled comparisons before 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. Why are seeds buried deeply in soil often less likely to emerge than seeds near the surface?
Explanation. Depth can alter the cues that trigger germination and increases the distance a seedling must grow before reaching light. Deep burial does not necessarily cause immediate death or prevent water uptake.
2. A researcher wants to compare seed-bank density at 0-2 cm and 8-10 cm depths. Which sampling method best supports that comparison?
Explanation. Replicated, depth-stratified soil cores preserve the depth information needed for comparison and reduce the influence of one unusual location. Mixing layers would erase the tested variable.
3. Which experiment most directly tests whether a shallow soil disturbance increases emergence from a preexisting seed bank?
Explanation. Matched controls, random assignment, and seed-rain exclusion isolate the effect of shallow disturbance on seedlings that arise from seeds already present in the soil.
4. After soil scraping, a plot has more emerging seedlings than an undisturbed plot. What is the most cautious conclusion?
Explanation. The comparison supports an effect on emergence in that study, but it does not establish universal outcomes, seed histories, or long-term population growth. Follow-up measurements can test mechanisms and survival.
5. How can surface disturbance sometimes promote seedling emergence?
Explanation. Disturbance can reposition seeds or alter microsites so that cues become available. It does not remove resource needs, genetic variation, or all competition.
6. A deep soil layer contains more viable seeds than a shallow layer, but fewer seedlings emerge from it in a greenhouse assay. Which explanation best fits both observations?
Explanation. Viability and emergence are different outcomes. A deeper layer can retain viable seeds while its physical conditions or depth limit the proportion that germinates and reaches the surface.
7. Which result would best show that a seedling-emergence response is caused by burial depth rather than by seed source?
Explanation. Using one mixed seed source and random depth assignment keeps seed source from being confounded with depth. Replication makes the depth comparison more reliable.
8. A survey finds that deeper seeds are less likely to emerge in plots with dense litter. What can the survey alone establish?
Explanation. Depth and litter may covary with moisture, canopy cover, species composition, or seed input. An experiment that independently manipulates depth or litter is needed for causal attribution.
9. Which observation most directly measures emergence rather than seed-bank size?
Explanation. Emergence is observed when a seedling appears above the soil surface. Seed counts and viability tests describe the seed bank, not the emergence outcome itself.
10. Why should an experiment measuring seed-bank emergence also track seedling survival after emergence?
Explanation. Emergent seedlings can still die from drought, competition, herbivory, or pathogens. Survival to a defined stage provides a more complete measure of recruitment.
11. Investigators bury mesh bags containing equal numbers of seeds at several depths and recover them after one year. Which measurement best distinguishes seed persistence from emergence?
Explanation. Viability of recovered seeds estimates how many seeds persisted alive at each depth. Adult height, bag color, and cloud cover do not directly measure seed persistence.
12. A field experiment moves some seeds from 10 cm depth to 1 cm depth and finds more emergence in the moved group. What additional feature would strengthen the claim that depth caused the difference?
Explanation. A handled deep-control group separates the effect of depth from effects of digging and moving seeds. Changing species or removing non-emergers would confound the comparison.
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FAQ
Why does seed depth matter in a soil seed bank?
Depth changes environmental cues, exposure to predators and pathogens, and the distance a seedling must grow to reach the surface. Its effects vary among species and sites.
Does more emergence mean a larger viable seed bank?
Not necessarily. Emergence depends on viable seed abundance, germination cues, burial depth, microsites, and post-germination conditions, so it is not a direct count of the whole seed bank.
How can ecologists test effects of disturbance on emergence?
They use replicated plots with matched controls, manipulate disturbance or depth, limit new seed rain when needed, and monitor emergence and later seedling survival.