LSAT 106 – Section 3 – Question 13

LSAT 106 - Section 3 - Question 13

June 1999

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Question QuickView	Type	Tags	Answer Choices	Curve	Question Difficulty	Psg/Game/S Difficulty	Explanation
PT106 S3 Q13	+LR	Resolve reconcile or explain +RRE	A 3% 162 B 4% 161 C 6% 165 D 16% 165 E 71% 168	137 153 170	+Harder	148.198 +SubsectionMedium

A recent study concludes that prehistoric birds, unlike modern birds, were cold-blooded. This challenges a widely held view that modern birds descended from warm-blooded birds. The conclusion is based on the existence of growth rings in prehistoric birds’ bodily structures, which are thought to be found only in cold-blooded animals. Another study, however, disputes this view. It concludes that prehistoric birds had dense blood vessels in their bones, which suggests that they were active creatures and therefore had to be warm-blooded.

"Surprising" Phenomenon

Prehistoric birds had growth rings suggesting they were cold-blooded animals, but dense blood vessels suggesting they were warm-blooded animals.

Objective

A hypothesis resolving this dispute must state a key similarity or difference between prehistoric birds and either cold-blooded or warm-blooded animals. It must allow for prehistoric birds to have both growth rings and dense blood vessels while being exclusively either cold-blooded or warm-blooded.

Some modern warm-blooded species other than birds have been shown to have descended from cold-blooded species.

This does not favor either possibility. Though other warm-blooded species descended from cold-blooded species, it is possible warm-blooded birds descended from warm-blooded prehistoric birds.

Having growth rings is not the only physical trait of cold-blooded species.

This is irrelevant information that does not favor either possibility. It is not stated whether prehistoric birds possessed any other traits of cold-blooded species.

Modern birds did not evolve from prehistoric species of birds.

In dispute is whether prehistoric birds were warm-blooded or cold-blooded, regardless of whether they were ancestors of modern birds. Both studies draw conclusions about prehistoric birds explicitly, so this does not favor either possibility.

Dense blood vessels are not found in all warm-blooded species.

This gets the desired relationship backward. It states that some warm-blooded species do not have dense blood vessels, but admits the possibility that all species with dense blood vessels are warm-blooded.

In some cold-blooded species the gene that is responsible for growth rings is also responsible for dense blood vessels.

This suggests prehistoric birds were cold-blooded. It implies that dense blood vessels are not necessarily evidence of warm-bloodedness, especially among animals with growth rings, calling into question the conclusion of the second study.

LSAT 106 – Section 3 – Question 13

LSAT 106 - Section 3 - Question 13

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LSAT PrepTest 106 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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