AP Biology: Pathogen Resistance Selection Pressure Management Practice Questions
Practice evaluating how restoration managers can preserve donor-source resistance without assuming that any defense will remain effective forever. These original questions connect resistance pyramiding and pathogen refuges with fitness costs, host and pathogen gene flow, pathogen population size, and adaptive thresholds based on repeated 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. Which restoration strategy is the clearest example of resistance pyramiding?
Explanation. Resistance pyramiding combines multiple defense mechanisms in the same host background. If the mechanisms act at different infection stages, a pathogen may need several compatible changes to overcome the combined defense.
2. Why might a carefully bounded pathogen refuge slow selection for a virulence allele that defeats a focal resistance mechanism?
Explanation. Pathogen refuges are populations or patches where the focal resistance does not dominate selection. They can preserve pathogen genotypes that lack costly virulence, although managers must balance this evolutionary effect against the risk of maintaining inoculum.
3. A resistant donor produces 20% fewer viable seeds than a susceptible donor when both are grown without the pathogen. What does this result most directly suggest?
Explanation. Lower reproduction in a pathogen-free comparison is evidence of a possible defense-associated fitness cost. Replication across environments is needed because fitness costs can depend on resources and climate.
4. A restored population receives abundant pollen from a nearby susceptible population. Which outcome is most plausible if resistance alleles are not strongly favored every generation?
Explanation. Host gene flow introduces alleles from neighboring populations. If incoming susceptible alleles are common and selection is weak or intermittent, resistance-allele frequency can decline across generations.
5. Why can a larger pathogen population size increase the chance that resistance is overcome?
Explanation. A larger pathogen population size usually produces more replication events. That increases mutation supply and the probability that a rare genotype able to exploit resistant hosts is already present or newly generated.
6. Which monitoring rule best represents adaptive thresholds for revising a donor deployment?
Explanation. Adaptive thresholds connect reproducible measurements to predefined actions. Combining disease burden with host fitness and requiring repeated evidence reduces reactions to isolated observations while still allowing timely adjustment.
7. Which experiment best tests whether two resistance mechanisms in a pyramid provide more durable protection than either mechanism alone?
Explanation. A factorial host comparison isolates the contribution of each mechanism and their combination. Repeated exposure to the same independently evolving pathogen lines tests whether the combined defense delays adaptation rather than merely lowering initial disease.
8. What is the main ecological trade-off when managers retain susceptible patches as pathogen refuges?
Explanation. A refuge can dilute the relative advantage of virulence alleles, especially when virulence has a fitness cost. The same susceptible hosts can also support pathogen reproduction, so placement, size, surveillance, and transmission risk matter.
9. A virulence allele evolves in one refugium and spores regularly disperse to the rest of the network. Which process could spread resistance breakdown among sites?
Explanation. Pathogen gene flow links local evolutionary outcomes. Dispersal of spores carrying a virulence allele can introduce it to other sites, where its frequency will depend on host resistance, transmission, drift, and any fitness cost.
10. Which intervention would most directly reduce the effective pathogen population before it generates large numbers of new variants?
Explanation. Removing infectious material before reproduction and interrupting dense susceptible-host connections can reduce pathogen reproduction and transmission. Lower effective population size can reduce mutation supply, although continued monitoring is necessary.
11. Disease severity exceeds its action threshold, but resistant donors still reproduce as well as controls for one survey. What is the most defensible response under a two-metric rule?
Explanation. When adaptive thresholds require both high disease and reduced fitness, one elevated disease survey does not satisfy the full trigger. Additional scheduled sampling preserves the decision rule while checking for a developing trend.
12. Monitoring shows that one resistance mechanism is failing, virulence is spreading between sites, and a second donor still has high multi-year fitness. Which response best manages future selection pressure?
Explanation. Selection-pressure management uses current evidence without treating another defense as permanent. Diversifying mechanisms and spatial deployment can reduce uniform selection, while continued threshold-based monitoring tests whether pathogen evolution or fitness costs change the preferred strategy.
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FAQ
What is selection-pressure management in pathogen resistance?
It is the deliberate use of resistance diversity, spatial design, pathogen population control, and monitoring rules to reduce strong uniform selection for resistance-breaking pathogen genotypes while preserving host fitness.
Why are resistance pyramiding and donor diversity not guarantees of durable resistance?
Pathogens can evolve, virulence alleles can move among sites, and defensive traits can impose context-dependent fitness costs. Replicated temporal monitoring is therefore still needed.
What makes an adaptive threshold useful?
A useful threshold names the metric, sampling design, trigger value, persistence requirement, and management response before the data are evaluated. This makes decisions repeatable and less sensitive to one unusual observation.