AP Biology: Climate Refugia Network Genetic Rescue Trade-offs Practice Questions
Practice evaluating when genetic rescue may strengthen a small population and when it can create new risks. These original AP Biology questions connect seed-dispersal restoration networks with genetic load, inbreeding depression, local adaptation, assisted gene flow, kinship structure, fitness validation, and transparent management trade-offs.
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Answer the questions below — you get instant feedback and a full explanation for each.
1. A small isolated plant population has low seed set and many related individuals. Which result would most directly support the idea that genetic load is contributing to its poor performance?
Explanation. Genetic load is the reduction in population fitness associated with harmful alleles. Lower survival in more-related crosses is evidence consistent with harmful recessive alleles being expressed, although environmental causes should also be tested.
2. Why can inbreeding depression become more likely after habitat fragmentation reduces movement among climate-refugia patches?
Explanation. Inbreeding depression is reduced fitness caused by mating among relatives, often because recessive deleterious alleles become homozygous. Isolation can reduce the supply of unrelated mates and make this process more likely.
3. Managers propose moving seeds from a warm nearby population into a cold refugium. Which observation gives the strongest reason to evaluate local adaptation before proceeding?
Explanation. A common-garden difference in frost survival suggests local adaptation to the cold refugium. Imported alleles might help some traits but could also reduce adaptation to local conditions, so the transfer needs a measured comparison.
4. Which description best distinguishes assisted gene flow from simply reconnecting habitat patches?
Explanation. Assisted gene flow is a deliberate movement intended to introduce genetic variation. A corridor can support dispersal without choosing the sources or timing of gene exchange, so the two interventions have different controls and risks.
5. Before selecting donors for a genetic-rescue trial, why should managers examine kinship structure in both donor and recipient populations?
Explanation. Kinship structure estimates how individuals are related. Sampling many close relatives can add less new diversity than sampling less-related individuals, so kinship information helps design a more informative and less biased transfer.
6. A donor population increases seedling survival in the first year after a transfer. What is the most appropriate next step for fitness validation?
Explanation. Fitness validation requires more than a short-term improvement. Preplanned comparisons across life stages and generations can test whether the transfer improves persistence rather than producing a temporary result or masking a later cost.
7. Which outcome would be most consistent with outbreeding depression after an assisted gene flow event?
Explanation. Outbreeding depression can occur when mixing disrupts coadapted gene combinations or introduces alleles poorly suited to the local environment. Lower reproductive success of crosses relative to both parental populations is a warning sign.
8. A restoration budget can fund either a broad corridor network or a small, monitored assisted gene flow trial. Which is the strongest framing of this management trade-off?
Explanation. A management trade-off weighs benefits, risks, uncertainty, and practical constraints. A monitored trial may reduce uncertainty about direct transfers, while corridors may support broader ecological movement; the choice depends on the evidence and objectives.
9. Why is a dispersal kernel useful when deciding whether assisted gene flow is necessary for a fragmented refugia network?
Explanation. A dispersal kernel describes how movement probability changes with distance. If the kernel and landscape data indicate that natural gene exchange is extremely unlikely, managers have a clearer reason to consider direct intervention.
10. Which experimental design best separates a possible assisted gene flow benefit from a difference that already existed among recipient patches?
Explanation. Comparable controls, baseline measurements, and consistent follow-up strengthen causal inference. Random assignment where feasible helps distinguish an intervention effect from preexisting differences in habitat quality or population condition.
11. What finding would most strongly justify revising the donor-selection rule in an adaptive genetic-rescue program?
Explanation. Replicated evidence of lower reproductive success after controlling for planting conditions indicates a meaningful risk. The program can revise donor criteria, such as matching environmental conditions or limiting genetic distance, and then test the new rule.
12. Which conclusion is most scientifically careful after a genetic-rescue pilot increases heterozygosity but has only one year of demographic data?
Explanation. Genetic diversity can be useful, but a single genetic metric and one year of data do not establish long-term population recovery. Continued monitoring of survival, recruitment, reproduction, and local conditions is needed for a cautious conclusion.
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FAQ
What is genetic rescue?
Genetic rescue is an increase in population performance after gene exchange introduces genetic variation into a small or inbred population. It is a hypothesis to test with fitness measurements, not a guarantee that every transfer will help.
Why can assisted gene flow have risks?
Introduced alleles may be poorly matched to local conditions or may disrupt coadapted gene combinations. Comparing donor sources, local adaptation, and offspring performance helps evaluate these risks.
How should a genetic-rescue project be validated?
Use preplanned controls or comparison donors, document kinship and baseline conditions, and follow survival, reproduction, recruitment, and genetic patterns across multiple years.