For much of the 20th century, paleontologists theorized that dinosaurs, like reptiles, were ectothermic, their body temperature regulated externally. These scientists, however, based their conclusions on faulty reasoning, claiming that scaly skin was common to all ectotherms (birds, which are ectothermic, do not have scaly skin) and that the dinosaur’s size could account for ectothermy (some adult dinosaurs weighed as little as ten pounds). Supplanting this theory is an entirely new line of thought: dinosaurs were actually mesothermic, neither warm- nor cold-blooded. By taking this middle ground, some paleontologists maintain that dinosaurs were faster than a similar-sized reptile yet did not require as much food as a similar-sized mammal. To substantiate this theory, paleontologists intend to study how birds, the dinosaur’s closest extant relative, might have at one time been mesothermic.
Read the passage and answer the following questions.
QUESTION: The two parts in parentheses serve to do which of the following?
Select the answer.
A) Summarize two claims that the author of the passage ultimately repudiates.
B) Highlight commonalities between birds and dinosaurs.
C) Provide rebuttals to commonly held views regarding physical aspects of dinosaurs.
D) Describe a recent theory that the author of the passage supports.
E) Furnish information regarding contradictory notions of dinosaur behavior.
Explanation:
Notice the structure of the sentence, “based their conclusions on faulty reasoning, claiming that ‘scaly skin was common to all ectotherms’ is the specific claim. Look at part in parentheses and how it relates to the part above: (birds, which are ectothermic, do not have scaly skin). This is a clear denial of the boldfaced part. The exact same thing happens with the second claim of scientists: “…the dinosaur’s size could account for ectothermy.”
Here is the objection (in parentheses) that states the boldfaced part is untrue: (some adult dinosaurs weighed as little as ten pounds). This points to answer (C): “Provides a rebuttal to a commonly held view regarding the physical aspects of dinosaurs” — the commonly held view is that dinosaurs are ectotherms simply because they have scaly skin.
Answer: C
QUESTION: Which of the following does the passage imply regarding birds?
Select ALL answers that apply.
A) They possess certain traits that are not common to all ectotherms.
B) They required more food than a similarly-sized mammal.
C) Over time they might have undergone a change in how they regulate body temperature.
Explanation:
The passage mentions that some scientists claimed that all ectotherms have scaly skin, However, birds, which are ectotherms, do not have scaly skin. Therefore, they have certain features that they do not share with other ectotherms, i.e., the lack of scaly skin. Answer: [A].
The passage mentions that dinosaurs require less food than a similar-sized mammal. However, there is no mention about how much food a bird requires. Sure, birds, like dinosaurs, might have been mesothermic, but mesothermy relates to body temperature regulation, not to the amount of food consumed.
The last sentence states that birds “might have at one time been mesothermic.” That is, they might have changed from mesotherms to ectotherms. From the first sentence, we learn that “ectothermic” describes body regulation. Therefore, birds possibly changed the way they regulate body temperate. Answer [C].
Answers: A, C