LSAT 121 – Section 1 – Question 17

LSAT 121 - Section 1 - Question 17

December 2005

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT121 S1 Q17
+LR
Flaw or descriptive weakening +Flaw
Part v. Whole +PvW
A
3%
157
B
1%
151
C
9%
158
D
11%
158
E
76%
165
144
152
161
 +Medium 145.604 +SubsectionMedium

Some classes of animal are so successful that they spread into virtually every ecosystem, whereas others gradually recede until they inhabit only small niches in geographically isolated areas and thereby become threatened. Insects are definitely of the former sort and ants are the most successful of these, ranging from the Arctic Circle to Tierra del Fuego. Hence, no species of ant is a threatened species.

Summarize Argument
The author concludes that there are no endangered species of ants. Why? Because insects in general are so successful that they spread into virtually every ecosystem, and ants are the most successful insect.

Identify and Describe Flaw
This is the cookie-cutter flaw of confusing part v. whole. The author observes that the biological family of ants is successful, and concludes that every individual ant species must be successful.
But some qualities can be true of a whole without being true of every part, or vice versa. Ants in general could be very successful, but some species of ants could still be endangered.

A
the Arctic Circle and Tierra del Fuego do not constitute geographically isolated areas
The author doesn’t presume that either is isolated; they’re used to demonstrate wide geographic range (extreme north vs. extreme south).
B
because ants do not inhabit only a small niche in a geographically isolated area, they are unlike most other insects
The author says that insects are definitely not the kind of animals limited to small niches, so this can’t be the flaw.
C
the only way a class of animal can avoid being threatened is to spread into virtually every ecosystem
This goes beyond what the argument states. The author says that two options for animal species are to go extinct or spread into virtually every ecosystem. He doesn’t indicate that those are the only two options.
D
what is true of the constituent elements of a whole is also true of the whole
This describes the part-to-whole flaw, but this is the reverse of what the author does. Instead, he commits a whole-to-part flaw; he attributes a property true of a whole (ants as a family) to each of its individual parts (individual species of ants).
E
what is true of a whole is also true of its constituent elements
This is the cookie-cutter whole-to-part flaw. The author takes for granted that a property true of a whole (ants as a whole are successful) is also true of the parts making up that whole (every individual ant species is successful). But that's flawed reasoning. Even if ants are generally successful, individual ant species could be endangered.

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LSAT PrepTest 121 Explanations

Section 1 - Logical Reasoning

Section 2 - Reading Comprehension

Section 3 - Reading Comprehension

Section 4 - Logical Reasoning

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