Question 116·Medium·Text Structure and Purpose
Geologist Adrian Park observes that the Devonian fossil record shows abrupt surges in plant diversity. In a recent paper, he first summarizes two prevailing hypotheses for this pattern: one links the diversification to a temporary rise in atmospheric oxygen, while the other attributes it to rapid tectonic uplift creating new habitats. Park then presents new isotopic data suggesting that both factors acted in concert, arguing that only their combined influence can account for the scale and timing of the fossil evidence.
Which choice best describes the overall structure of the text?
For structure-and-purpose questions, first paraphrase what the passage does in order: identify what the author is doing in the beginning (introducing a problem, stating a claim, summarizing views) and then what they do next (providing evidence, proposing a new idea, contrasting positions). Ignore technical details and focus on function words like "first," "then," "however," and "therefore." Once you have a simple pattern like "summarizes existing explanations, then proposes a new synthesis," eliminate any answer that adds steps not in the passage (e.g., predictions, detailed methods) or mislabels the author’s moves (e.g., choosing one theory instead of combining them). Pick the answer whose description most closely matches your paraphrased pattern.
Hints
Focus on the middle sentence
Look closely at the sentence that starts with "In a recent paper, he first summarizes…" and ask: What exactly is Park doing here—telling a story over time, comparing popularity, or briefly stating existing ideas?
Examine the role of the new isotopic data
In the last sentence, what is the purpose of the isotopic data—describing step-by-step procedures, choosing one idea over another, or building some kind of new argument?
Turn the passage into a simple pattern
In your own words, finish this pattern: "First, Park does ___ with two earlier ideas; then, he uses new data to ___ about them." Once you have that pattern, look for the choice that matches it most closely.
Step-by-step Explanation
Identify what the first part of the passage does
Look at the middle sentence:
"In a recent paper, he first summarizes two prevailing hypotheses for this pattern: one links the diversification to a temporary rise in atmospheric oxygen, while the other attributes it to rapid tectonic uplift creating new habitats."
Here, Park is not describing experiments in detail or giving a timeline of a whole field. He is summarizing two existing hypotheses that other scientists already use to explain the observed pattern in the fossil record.
Identify what the second part of the passage does
Now focus on the final sentence:
"Park then presents new isotopic data suggesting that both factors acted in concert, arguing that only their combined influence can account for the scale and timing of the fossil evidence."
This shows Park using new isotopic data to argue that both previously mentioned factors work together. He is putting forward a new explanation that blends the two earlier hypotheses, not simply choosing one over the other and not explaining how to replicate a method.
Summarize the overall structure in your own words
Putting the two parts together, the passage structure is:
- First: introduce an observed phenomenon (surges in plant diversity) and summarize two existing hypotheses that try to explain it.
- Then: use new data to argue for a combined explanation that uses elements of both hypotheses.
Keep this simple description in mind and compare it directly to each answer choice.
Match your summary to the best answer choice
Now compare your summary to the options:
- There is no chronological history of a scientific field or prediction about the future, so the option about recounting a field’s development and predicting directions does not fit.
- Park does not say one theory is popular and the other less known, nor does he reject one and declare the other definitively correct.
- He does not describe an experimental method step by step or talk about how others can replicate it.
Only the choice that describes summarizing two established explanations and then proposing a new explanation that combines both matches the passage’s structure.
Therefore, the correct answer is: “The text summarizes two established explanations for an observed phenomenon and then proposes a new explanation that combines elements of both.”