LSAT 143 – Section 3 – Question 16

LSAT 143 - Section 3 - Question 16

June 2015

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT143 S3 Q16
+LR
Flaw or descriptive weakening +Flaw
Conditional Reasoning +CondR
A
88%
164
B
6%
159
C
3%
158
D
2%
160
E
1%
156
129
140
152
 +Easier 147.721 +SubsectionMedium

Theorist: To be capable of planned locomotion, an organism must be able both to form an internal representation of its environment and to send messages to its muscles to control movements. Such an organism must therefore have a central nervous system. Thus, an organism incapable of planned locomotion does not have a central nervous system.

Summarize Argument
The author concludes that an organism incapable of planned locomotion does not have a central nervous system. This is based on the fact that, in order to be capable of planned locomotion, an organism must have a central nervous system.

Identify and Describe Flaw
The author confuses a sufficient condition for having a central nervous system (capable of planned locomotion) with a necessary condition. This overlooks the possibility that organisms that can’t do planned locomotion can still have a central nervous system. (Note that this can also be described as confusing a necessary condition with a sufficient condition.)

A
confuses a necessary condition for an organism’s possessing a capacity with a sufficient one
The confuses a necessary condition (having central nervous system) for an organism’s possessing a capacity (capable of planned locomotion) with a sufficient one. This overlooks the possibility that an animal can have a central nervous system without planned locomotion.
B
takes for granted that organisms capable of sending messages from their central nervous systems to their muscles are also capable of locomotion
There are no assumptions about sending messages “from their central nervous system.” Although the author does assume that organisms with a central nervous system are capable of planned locomotion, that doesn’t imply the author thinks the nervous system sends message to muscles.
C
presumes, without providing justification, that planned locomotion is the only biologically useful purpose for an organism’s forming an internal representation of its environment
The argument doesn’t make assumptions about what is “biologically useful.” The argument is based on a misinterpretation of the fact that a central nervous system is necessary for planned locomotion. What is biologically useful has no part on the reasoning.
D
takes for granted that adaptations that serve a biologically useful purpose originally came about for that purpose
The argument doesn’t make assumptions about what is “biologically useful” or the original purpose of a biologically useful adaptation. The argument is based on a misinterpretation of the fact that a central nervous system is necessary for planned locomotion.
E
presumes, without providing justification, that an internal representation of its environment can be formed by an organism with even a rudimentary nervous system
The argument doesn’t make any assumptions about a “rudimentary nervous system.” We don’t know whether any organism has a rudimentary nervous system. It’s not clear whether a central nervous system is rudimentary or not.

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LSAT PrepTest 143 Explanations

Section 1 - Logical Reasoning

Section 2 - Reading Comprehension

Section 3 - Logical Reasoning

Section 4 - Logical Reasoning

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