LSAT 115 – Section 2 – Question 16

LSAT 115 - Section 2 - Question 16

December 2002

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT115 S2 Q16
+LR
Argument part +AP
A
2%
156
B
7%
157
C
16%
158
D
67%
164
E
9%
156
145
155
165
 +Harder 148.811 +SubsectionMedium

Biologists agree that human beings evolved from a fish, but they disagree about which species of fish. Since biologists agree that frogs are definitely related to the species of fish from which human beings evolved, on the basis of a close match between the mitochondrial DNA of lungfish and that of frogs Dr. Stevens-Hoyt claims that this ancestor must be lungfish. Dr. Grover, on the other hand, contends that mitochondrial DNA evolves too rapidly to be a reliable indicator of relationships between species over long periods of time, and citing the close chemical match between the hemoglobin of coelacanths (a saltwater fish) and that of tadpoles, claims that human beings must be descended from coelacanths.

Summarize Argument: Counter-Position
The author concludes that biologists disagree about which species of fish from which humans evolved. The author proceeds to outline two biologists’ perspectives. The biologists agree that frogs are related to this species of fish. Dr. Stevens-Hoyt says that lungfish are the ancestor of humans because the mitochondrial DNA of lungfish is similar to that of frogs. Dr. Grover rejects Dr. Stevens-Hoyt because mitochondrial DNA evolves too rapidly to demonstrate relationships between species. Rather, Dr. Stevens believes that coelacanths are the ancestor of humans because the hemoglobin of coelacanths matches that of tadpoles.

Identify Argument Part
The proposition in the question stem refers to a point of agreement between the scientists.

A
Since it implies that human beings are not descended from lungfish, it is cited as evidence against the claim that humans are descended from lungfish.
The proposition in the question stem does not imply that human beings are not descended from lungfish. The author does not take a side in this dispute; the author simply provides a brief outline of two different theories.
B
Since it implies that human beings are not descended from coelacanths, it is offered as evidence against the claim that human beings are descended from coelacanths.
The proposition in the question stem does not imply that human beings are not descended from coelacanths. The author does not take a side in this dispute; the author simply provides a brief outline of two different theories.
C
It is offered as evidence for the contention that human beings must be descended from either lungfish or coelacanths.
The author does not say definitively that either Dr. Stevens-Hoyt or Dr. Grover must be correct; the author is simply outlining two different theories. The author does not contend that humans must be descended from either lungfish or coelacanths.
D
It is an assumption that both parties to the dispute use as a starting point for their arguments about human evolution.
Both biologists use the fact that frogs are related to the species of fish from which humans evolved as a premise for their arguments. This is a point of agreement; while they draw different conclusions from this information, it is a key premise for each argument.
E
It implies that either a match of mitochondrial DNA or a match of hemoglobin between lungfish and coelacanths would show that human beings evolved from one of these two species.
The claim in (E) is not an implication made by the argument.

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LSAT PrepTest 115 Explanations

Section 1 - Reading Comprehension

Section 2 - Logical Reasoning

Section 3 - Reading Comprehension

Section 4 - Logical Reasoning

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