Pteropods are small swimming snails with thin, delicate calcium carbonate shells. These animals are thought to be especially vulnerable to...
GMAT Craft and Structure : (Structure) Questions
Pteropods are small swimming snails with thin, delicate calcium carbonate shells. These animals are thought to be especially vulnerable to ocean acidification due to calcium carbonate's susceptibility to dissolution at lower pH values. Victoria L. Peck and colleagues recently found that the periostracum (a protective coating on pteropods' outer shells) prevents this dissolution when intact. Moreover, the team was surprised to discover that even when the periostracum is breached, pteropods can still mitigate damage by rebuilding the inner shell wall.
Which choice best describes the main purpose of the text?
Step 1: Decode and Map the Passage
Part A: Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Pteropods are small swimming snails with thin, delicate calcium carbonate shells." |
|
| "These animals are thought to be especially vulnerable to ocean acidification due to calcium carbonate's susceptibility to dissolution at lower pH values." |
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| "Victoria L. Peck and colleagues recently found that the periostracum (a protective coating on pteropods' outer shells) prevents this dissolution when intact." |
|
| "Moreover, the team was surprised to discover that even when the periostracum is breached, pteropods can still mitigate damage by rebuilding the inner shell wall." |
|
Part B: Provide Passage Architecture & Core Elements
Main Point: Research has revealed that pteropods have protective mechanisms that may make them less vulnerable to ocean acidification than previously thought.
Argument Flow: The passage begins by establishing what pteropods are and why scientists were concerned about their vulnerability to ocean acidification. It then presents recent research findings that reveal two protective mechanisms these organisms possess, suggesting the original concern may have been overstated.
Step 2: Interpret the Question Precisely
What's being asked? The main purpose of the entire text
What type of answer do we need? A statement that captures why this text was written - what it's trying to accomplish
Any limiting keywords? "Main purpose" means we need the overarching goal, not just what happens in one part
Step 3: Prethink the Answer
- The correct answer should capture that this text is fundamentally about presenting research that challenges or reduces a scientific concern
- We started with scientists thinking pteropods were especially vulnerable to ocean acidification, but then the research showed they have not just one but two protective mechanisms
- The purpose isn't to discuss general pteropod biology or call for more research - it's specifically to present findings that suggest the worry about ocean acidification might not be as serious as initially thought
- Says the text calls for additional research on survival mechanisms
- The passage presents completed research findings, it doesn't call for more research
- Claims the text discusses calcium carbonate's role in protecting the periostracum
- This reverses the actual relationship - the periostracum protects the calcium carbonate shell, not the other way around
- Says the text addresses how ocean acidification has altered pteropod behavior over time
- The passage discusses protective shell mechanisms, not behavioral changes
- Captures that the text presents research findings that suggest a concern may be unwarranted
- Matches our analysis: we start with a concern (vulnerability to acidification) but then get findings showing protective mechanisms