LSAT 106 | Section 3 | Logical Reasoning: Q13

LR Question 13 Explanation

QUESTION TEXT: A recent study concludes that prehistoric birds…

QUESTION TYPE: Strengthen

ARGUMENTS: One side says that prehistoric birds were cold blooded. They had growth rings, which have so far only been found in cold blooded animals.

The other side thinks prehistoric birds were warm blooded. They had dense blood vessels in their bones, which are usually a sign of activity and warm bloodedness.

ANALYSIS: This is a rare question type. We have to choose one side over the other.

Each side has only one piece of evidence. The two pieces of evidence are growth rings and dense blood vessels. Make sure you know the role each plays.

The right answer hardly strengthens side one, but the question stem just asks which answer “most” helps to resolve the dispute.

___________

1. This slightly supports the cold-blooded side. It’s possible that prehistoric birds were cold blooded. But this is very far from resolving the dispute.
    
   Every warm blooded species has cold blooded ancestors, in fact.
2. Clearly, cold blooded species will have other physical traits: bones, hearts, lungs, etc.
    
   Telling us this obvious fact resolves nothing.
3. It’s implied that the first group thinks their study showed that modern birds’ ancestors were cold-blooded prehistoric birds. The second group think modern birds descended from warm blooded prehistoric birds.
    
   So this hurts both theories, and does nothing to show whether prehistoric birds were warm or cold blooded.
4. This does nothing. The second group already agrees that dense blood vessels only suggest warm-bloodedness.
5. CORRECT. This helps the first group, somewhat. The growth rings could have caused the dense blood vessels.
    
   Note that the word “some” means this provides only weak support for the first group. But it at least weakens the connection between dense blood vessels and warm bloodedness.