Question 77·Medium·Inferences
Field botanists studying a rare forest orchid have shown that its seeds germinate only in the presence of a specific soil fungus. In recently logged plots, they found far fewer seedlings than in nearby unlogged plots, even though adult orchid numbers were similar in both areas. These observations most strongly suggest that the logging likely ____.
Which choice most logically completes the text?
For SAT Reading & Writing inference questions like this, first restate the key facts in your own words, paying attention to contrasts (here, seedlings vs. adults and logged vs. unlogged). Identify what type of change the question is asking about (cause of fewer seedlings) and which detail is central (the soil fungus for germination). Then quickly test each answer: eliminate any that (1) contradict a stated fact, (2) focus on the wrong thing (like adult numbers instead of seedlings), or (3) introduce new ideas (like herbivores or light) without support. Choose the option that most directly and specifically explains the given pattern using only the information in the passage.
Hints
Focus on seedlings vs. adults
Notice the contrast the passage makes: seedling numbers are very different between logged and unlogged plots, but adult orchid numbers are similar. What does that tell you about which life stage is most affected?
Use the detail about the soil fungus
The botanists discovered that seeds can germinate only with a specific soil fungus. Which answer choices deal with something that could affect that germination requirement?
Eliminate answers that contradict given facts
Check each option against the statement that adult orchid numbers are similar in logged and unlogged plots. Any choice that would clearly change adult numbers is less likely to be correct.
Look for the strongest logical connection
The stem says "most strongly suggest." Which option gives a cause that directly explains why logging is linked to fewer seedlings, using only information provided in the passage?
Step-by-step Explanation
Restate the key facts from the passage
Break the passage into its two main scientific observations:
- Field botanists found that the orchid’s seeds germinate only when a specific soil fungus is present.
- In recently logged plots, there are far fewer seedlings than in nearby unlogged plots, even though adult orchid numbers are similar in both.
So we know:
- Seedlings depend on the fungus.
- Logging is associated with fewer seedlings, not fewer adults.
Decide what must have changed in the logged plots
Because the number of adult orchids is similar in both logged and unlogged plots, logging did not dramatically reduce the number of adults.
Yet there are fewer seedlings in logged plots. Seedlings come from seeds that managed to germinate.
So whatever logging did seems to have affected the germination stage (the process from seed to seedling), not the adult plants themselves. And the passage tells us germination depends on the soil fungus.
Test each answer choice against the evidence
Now ask of each option: Does this explain “fewer seedlings but similar adults,” using information given in the passage?
- Any choice that would mainly affect adult orchids (making them fewer) conflicts with the line saying adult numbers are similar.
- Any choice that talks about things not mentioned (like new animals) without connecting to the fungus or germination is not strongly supported.
- The best choice will give a plausible way logging could reduce seedling numbers while leaving adult numbers about the same, and it should connect to the special requirement for fungus-dependent germination.
Match the best-supported cause with the observations
The only option that directly connects logging to fewer seedlings (while keeping adult numbers similar) and uses the key fact that seeds need a soil fungus is:
D) disrupted the soil conditions that support the fungus required for the orchid's germination.
If logging disrupted the soil or the fungus, fewer seeds could germinate into seedlings, explaining the large drop in seedlings without changing the current number of adults.