Question 12·Hard·Command of Evidence
Effects of Mycorrhizal Fungi on 3 Plant Species
| Plant species | Mycorrhizal host | Average mass of plants grown in soil containing mycorrhizal fungi (g) | Average mass of plants grown in soil treated to kill fungi (g) |
|---|---|---|---|
| Corn | yes | 15.1 | 3.8 |
| Marigold | yes | 10.2 | 2.4 |
| Broccoli | no | 7.5 | 7 |
Mycorrhizal fungi in soil benefit many plants, substantially increasing the mass of some. A student conducted an experiment to illustrate this effect. The student chose three plant species for the experiment, including two that are mycorrhizal hosts (species known to benefit from mycorrhizal fungi) and one nonmycorrhizal species (a species that doesn’t benefit from and may even be harmed by mycorrhizal fungi). The student then grew several plants from each species both in soil containing mycorrhizal fungi and in soil that had been treated to kill mycorrhizal and other fungi. After several weeks, the student measured the plants’ average mass and was surprised to discover that _____.
Which choice most effectively uses data from the table to complete the text?
For SAT questions that ask what a researcher was “surprised” to find in a table or graph, first read the short description to understand the expectation (what should happen) for each group. Then, scan the data to see which result goes against that expectation. Finally, test each answer choice against the actual numbers: quickly eliminate any option that doesn’t match the data exactly or that just restates an expected, obvious pattern, and choose the one that is both factually correct and unexpected based on the setup.
Hints
Focus on which species were expected to benefit
Look at the “Mycorrhizal host” column in the table. Which two species are listed as “yes,” and which one is listed as “no”? How does the passage say these two groups should respond to mycorrhizal fungi?
Use the idea of “surprised” to predict the pattern
The student already knows that host plants usually benefit from mycorrhizal fungi. Given that, what kind of result for the nonmycorrhizal species would go against expectations and therefore be surprising?
Check each option against the numbers in the table
For each answer choice, carefully compare the masses given (with fungi vs treated to kill fungi) to the actual numbers in the table. Eliminate any choice that doesn’t match the data exactly, or that simply describes an expected benefit for a mycorrhizal host species.
Step-by-step Explanation
Understand the setup of the experiment
First, read the description above the table. Two species (corn and marigold) are mycorrhizal hosts, which means they are known to benefit from mycorrhizal fungi. One species (broccoli) is nonmycorrhizal, which means it “doesn’t benefit from and may even be harmed by” the fungi. The student expects hosts to do better with fungi, and the nonhost to show no benefit or even be harmed.
Identify what would be surprising
Because hosts are supposed to benefit, it is not surprising if corn and marigold grow much larger in soil with fungi than in soil without fungi. It would be surprising if the nonmycorrhizal species, broccoli, seemed to benefit from the fungi (since it is expected not to benefit, or even be harmed). So you should pay special attention to broccoli’s numbers in both soil types.
Compare the data for each plant
Now read the table:
- Corn: with fungi 15.1 g, without fungi 3.8 g (big increase with fungi).
- Marigold: with fungi 10.2 g, without fungi 2.4 g (big increase with fungi).
- Broccoli: with fungi 7.5 g, without fungi 7 g (a small increase with fungi). Next, check each answer choice against these numbers and against what the student expected (hosts benefit; nonhost does not). Eliminate any answer that is either factually wrong according to the table or describes something predictable rather than surprising.
Match the surprising result to the correct choice
Only one option correctly describes a result that both matches the table and would reasonably surprise the student: the nonmycorrhizal species, broccoli, actually had a slightly higher average mass in soil containing mycorrhizal fungi ( g) than in soil treated to kill fungi ( g). This is unexpected because broccoli was not supposed to benefit from the fungi. Therefore, the correct answer is: “broccoli grown in soil containing mycorrhizal fungi had a slightly higher average mass than broccoli grown in soil that had been treated to kill fungi.”