Herbivorous sauropod dinosaurs could grow more than 100 feet long and weigh up to 80 tons, and some researchers have...
GMAT Information and Ideas : (Ideas) Questions
Herbivorous sauropod dinosaurs could grow more than 100 feet long and weigh up to 80 tons, and some researchers have attributed the evolution of sauropods to such massive sizes to increased plant production resulting from high levels of atmospheric carbon dioxide during the Mesozoic era. However, there is no evidence of significant spikes in carbon dioxide levels coinciding with relevant periods in sauropod evolution, such as when the first large sauropods appeared, when several sauropod lineages underwent further evolution toward gigantism, or when sauropods reached their maximum known sizes, suggesting that ______
Which choice most logically completes the text?
fluctuations in atmospheric carbon dioxide affected different sauropod lineages differently.
the evolution of larger body sizes in sauropods did not depend on increased atmospheric carbon dioxide.
atmospheric carbon dioxide was higher when the largest known sauropods lived than it was when the first sauropods appeared.
sauropods probably would not have evolved to such immense sizes if atmospheric carbon dioxide had been even slightly higher.
Step 1: Decode and Map the Passage
Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Herbivorous sauropod dinosaurs could grow more than 100 feet long and weigh up to 80 tons," |
|
| "and some researchers have attributed the evolution of sauropods to such massive sizes to increased plant production resulting from high levels of atmospheric carbon dioxide during the Mesozoic era." |
|
| "However, there is no evidence of significant spikes in carbon dioxide levels coinciding with relevant periods in sauropod evolution," |
|
| "such as when the first large sauropods appeared, when several sauropod lineages underwent further evolution toward gigantism, or when sauropods reached their maximum known sizes," |
|
Step 2: Interpret the Question Precisely
This is a fill-in-the-blank question asking us to choose the best logical connector. The answer must create the right relationship between what comes before and after the blank.
Step 3: Prethink the Answer
- The logic is straightforward: If high CO2 levels caused sauropod gigantism, we would expect to see CO2 spikes during the key periods when this gigantism evolved
- But we do not see those spikes during any of the crucial periods
- This absence of evidence where we would most expect to find it strongly suggests the CO2 theory is wrong
- The right answer should reject or weaken the connection between atmospheric CO2 and sauropod size evolution
fluctuations in atmospheric carbon dioxide affected different sauropod lineages differently.
✗ Incorrect
- Claims CO2 fluctuations affected different sauropod lineages differently
- This misses the point - the passage shows there were no significant CO2 spikes at all during key periods
the evolution of larger body sizes in sauropods did not depend on increased atmospheric carbon dioxide.
✓ Correct
- States that sauropod size evolution did not depend on increased atmospheric CO2
- This directly follows from the evidence - no CO2 spikes during key evolutionary periods means CO2 likely was not the driving factor
atmospheric carbon dioxide was higher when the largest known sauropods lived than it was when the first sauropods appeared.
✗ Incorrect
- Claims CO2 was higher when largest sauropods lived versus when first ones appeared
- This contradicts the passage's point about lack of evidence for CO2 spikes during relevant periods
sauropods probably would not have evolved to such immense sizes if atmospheric carbon dioxide had been even slightly higher.
✗ Incorrect
- Suggests even higher CO2 would have prevented sauropod gigantism
- This is backwards - it accepts the CO2 connection when the evidence suggests rejecting it entirely