Question 198·Hard·Rhetorical Synthesis
While preparing a presentation, a student has gathered the following notes:
• Sea otters prey heavily on sea urchins, keeping urchin populations in check.
• When urchin numbers explode, they overgraze kelp forests, sometimes eliminating them entirely.
• Kelp forests provide habitat for many fish species and play a role in long-term carbon storage.
• Marine ecologist Jane Watson refers to sea otters as a “keystone species” in Pacific Northwest coastal ecosystems.
The student wants to explain why sea otters are considered a keystone species in Pacific Northwest kelp ecosystems. Which choice most effectively uses relevant information from the notes to achieve this purpose?
For rhetorical synthesis questions based on notes, start by restating the task in your own words (what exactly needs to be explained or shown). Then quickly turn the notes into a simple cause-and-effect or main-idea outline and look for the choice that (1) matches that outline, (2) keeps the correct focus (here, explaining why sea otters are keystone species), (3) uses multiple relevant points from the notes, and (4) avoids adding new, unsupported claims. Eliminate any option that leaves out the main actor, changes the reason, or only restates a small piece of the information.
Hints
Focus on the purpose
The student wants to explain why sea otters are considered a keystone species. Ask yourself: which choice clearly gives a cause-and-effect reason for their importance, not just background facts?
Use the whole chain of notes
Look back at the notes and trace the relationships: sea otters, sea urchins, kelp forests, fish habitat, and carbon storage. Which option connects these ideas into one explanation?
Check for missing or irrelevant focus
Eliminate any answer that does not mention sea otters at all, that only describes kelp forests, or that just says who studies sea otters without explaining their ecological role.
Watch out for unsupported causes
Make sure the stated reason sea otters are important actually comes from the notes (for example, controlling urchins), not from an assumption that is never mentioned (like simply living in kelp forests).
Step-by-step Explanation
Understand the task
The question asks for a sentence that explains why sea otters are considered a keystone species in Pacific Northwest kelp ecosystems. So the correct answer must:
- Mention sea otters and the idea of a keystone species.
- Explain the reason they are so important (their ecological impact), not just describe kelp or name a scientist.
Summarize the key information from the notes
From the notes, build the cause-and-effect chain:
- Sea otters prey heavily on sea urchins, keeping urchin populations in check.
- If urchin populations explode, they overgraze kelp forests and can eliminate them.
- Kelp forests provide habitat for many fish species and help store carbon.
- Jane Watson calls sea otters a "keystone species" in these ecosystems. The explanation we want should connect sea otters → urchins → kelp forests → fish and carbon storage.
Eliminate choices that don’t mention sea otters as keystone species
Check which options clearly connect to sea otters’ special role:
- Choice A talks about sea urchins and kelp forests but never mentions sea otters or keystone species.
- Choice B mentions kelp forests and that Jane Watson studies sea otters, but does not explain why sea otters are a keystone species.
- Choice C says sea otters are vital but gives the reason as simply living in kelp forests, which is not supported by the notes. Only one choice both labels sea otters as a keystone species and gives the correct reason.
Confirm the choice that uses multiple relevant notes accurately
The correct answer must:
- Use Jane Watson’s term "keystone species."
- Show that sea otters eat sea urchins, keeping their numbers in check.
- Show that this protects kelp forests, which shelter many fish and store carbon. Choice D does all of this: it states that Jane Watson calls sea otters a "keystone species" because, by feeding on sea urchins, they stop the urchins from destroying kelp forests that support diverse fish and store carbon. Therefore, D is the best answer.