Question 124·200 Super-Hard SAT Reading Questions·Information and Ideas
In salt marshes, cordgrass seedlings often occur in rings around mature plants, a pattern generally interpreted as evidence that the adults facilitate seedling establishment. Ecologists released equal numbers of marked cordgrass seeds beside live adult clumps, beside resin replicas matching the clumps' stem arrangement, and on adjacent bare sediment. After several high tides, the live clumps and replicas had trapped similarly high numbers of seeds, whereas the bare areas retained few. Yet among the trapped seeds that germinated, survival through midsummer was lower beside live clumps than beside replicas; measurements showed comparable soil moisture and salinity but substantially less light beside the live clumps. The ecologists therefore hypothesize that _____
Which choice most logically completes the text?
For an inference question involving an experiment, identify what each comparison isolates. Here, the replicas test whether being a living plant is necessary for seed retention, while the later survival data test whether proximity to a living plant remains beneficial. The correct inference must account for both stages without assuming that clustering proves successful establishment.
Hints
Identify the control
Consider why the ecologists included resin replicas with the same stem arrangement as the live clumps.
Compare retention results
Ask what live clumps and replicas share that bare sediment lacks.
Distinguish retention from survival
Do not assume that a location where many seeds collect must also be a location where seedlings thrive.
Step-by-step Explanation
Separate the stages studied
The experiment measured two distinct stages: the initial retention of seeds after tides and the later survival of seedlings that germinated.
Interpret the replica comparison
Live clumps and structurally similar replicas trapped equally high numbers of seeds. Because the replicas were not living plants, this result points to a shared physical feature, such as stem arrangement, as the cause of retention.
Evaluate the later outcome
Seedlings survived at a lower rate beside live clumps than beside replicas. The comparable moisture and salinity but lower light near live clumps suggest that proximity to living adults can impose a later cost.
Complete the inference
The best completion is rings of seedlings can arise through passive capture by adults' physical structure even though living adults reduce the seedlings' later survival.