Question 64·Easy·Inferences
Marine biologists investigating how habitat structure affects fish survival set up two identical large seawater tanks and stocked each with equal numbers of two small reef fish species. One species typically shelters among branching corals, while the other usually hovers in open water above the reef. In one tank, the researchers installed artificial branching structures; the other tank was left open. After releasing a predator fish into each tank and waiting one hour, they counted how many individuals of each species remained.
- Tank with branches: 90% of the sheltering species and 40% of the hovering species survived.
- Open tank: 30% of the sheltering species and 35% of the hovering species survived.
These results most strongly suggest that ____
Which choice most logically completes the text?
For SAT questions that ask what experimental results "most strongly suggest," first restate the setup in your own words: what changed (the independent variable) and what was measured (the outcome). Compare the key numbers or trends for each group, then look for the central pattern (who benefits, who doesn’t, which condition is better). Next, scan the choices and eliminate any that (1) use extreme language like "always" or "equally" not justified by the data, (2) go beyond the experiment’s scope (e.g., from tanks to natural reefs), or (3) contradict the numbers given. Choose the answer that directly matches the observed pattern without overgeneralizing.
Hints
Focus on the data pattern
Look carefully at the survival percentages for each species in each tank. Which species’ survival changes the most between the tank with branches and the open tank?
Think about who benefits from branches
Ask yourself: For which type of fish do the branching structures seem to make a big positive difference, and for which type do they make little difference?
Watch for overgeneralizations
Check each answer for words like "always," "equally," or references to "natural reef settings" that may go beyond what this specific tank experiment can actually show.
Step-by-step Explanation
Understand the experiment setup
Two small reef fish species are tested:
- Species 1: usually shelters among branching corals.
- Species 2: usually hovers in open water above the reef.
There are two tanks:
- One tank has artificial branching structures.
- The other tank is open (no structures).
A predator is added to each tank, and after one hour, the researchers count how many fish of each species survive.
Compare survival for the sheltering species
Look at the species that typically shelters among branching corals:
- In the tank with branches: 90% survived.
- In the open tank: 30% survived.
That is a very large increase in survival when branches are present (90% vs. 30%), suggesting the branches have a strong protective effect for this species.
Compare survival for the hovering species
Now look at the species that usually hovers in open water above the reef:
- In the tank with branches: 40% survived.
- In the open tank: 35% survived.
For this species, survival is almost the same in both tanks (40% vs. 35%), so the branching structures do not make nearly as big a difference.
Match the pattern to the best-supported conclusion
The main pattern is that adding branching structures greatly helps the species that normally uses them for shelter, but helps the hovering species only a little. The best conclusion will:
- Focus on the sheltering species.
- Say that these fish are better protected when branching structures are present.
- Avoid broad claims about all reef fish, all situations, or natural reefs.
The choice that does this is: "fish that normally seek cover among branching corals are better protected from predators when such structures are present."