While researching a topic, a student has compiled the following notes:
- In 2005, paleontologist Mary Schweitzer and her colleagues reported finding soft, flexible, vessel-like structures in an approximately 68-million-year-old Tyrannosaurus rex femur.
- Because proteins generally break down over time, many scientists doubted that original dinosaur material could survive for so long.
- Some researchers proposed that the structures resulted from modern contamination or bacterial biofilms.
- In 2007, Schweitzer’s team used mass spectrometry to identify collagen peptide sequences in samples from the fossil.
- Some of the sequences resembled collagen from chickens, a result consistent with the evolutionary relationship between birds and dinosaurs.
- The chemical results strengthened the interpretation that material originating from the dinosaur had been preserved.
The student wants to introduce Schweitzer’s research to a general audience by explaining why the 2005 finding drew skepticism and how a later test addressed that skepticism. Which choice most effectively uses relevant information from the notes to accomplish this goal?
For rhetorical-synthesis questions, separate the stated goal into distinct requirements and compare each choice against all of them. Select the choice that accurately connects the relevant evidence and its significance rather than one that merely reports a true but incomplete detail from the notes.
Hints
Break down the goal
Identify the two tasks the response must perform: explain the doubt surrounding the initial report and describe evidence from a subsequent investigation.
Find the competing explanations
Consider why the age of the fossil led some researchers to propose an origin other than preserved dinosaur material.
Evaluate completeness
Eliminate choices that discuss only the original finding, only the skepticism, or only the later test.
Step-by-step Explanation
Identify the two required elements
The response must explain why the 2005 finding drew skepticism and describe how a later test addressed that skepticism.
Locate the relevant evidence
Scientists doubted that dinosaur proteins could survive for approximately 68 million years and proposed contamination or bacterial biofilms as alternative explanations. Schweitzer’s team later used mass spectrometry to detect collagen peptide sequences in the fossil.
Connect the evidence to its significance
The detected collagen provided chemical evidence supporting the interpretation that some material originating from the dinosaur had been preserved. Thus, the later test directly addressed the concern that the structures were merely contamination.
Choose the complete synthesis
The best choice combines the reason for the skepticism, the later mass-spectrometry test, and the significance of the collagen evidence. The remaining choices omit at least one required part of the student’s goal.