LSAT 105 – Section 1 – Question 19

LSAT 105 - Section 1 - Question 19

February 1999

You need a full course to see this video. Enroll now and get started in less than a minute.

Request new explanation

Target time: 1:57

This is question data from the 7Sage LSAT Scorer. You can score your LSATs, track your results, and analyze your performance with pretty charts and vital statistics - all with a Free Account ← sign up in less than 10 seconds

Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT105 S1 Q19
+LR
Except +Exc
Strengthen +Streng
A
5%
160
B
10%
162
C
35%
165
D
42%
168
E
7%
163
156
170
180
 +Hardest 147.243 +SubsectionMedium

Paleontologist: It is widely, but falsely, held that life began in the ocean and did not exist on land until half a billion years ago. Traces of carbon 14 have been found throughout certain 1.2-billion-year-old rocks in North America. Carbon 14 is extracted by plants and microbes from the atmosphere to fuel their chemical reactions, and is then released when the plants and microbes die.

Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that life existed on land earlier than half a billion years ago or that life began on land. This is based on the fact that traces of carbon 14 have been found throughout certain 1.2-billion-year old rocks. Carbon 14 is extracted from the atmosphere by living things and is then released when those living things die.

Notable Assumptions
The author assumes that there’s no other explanation for the presence of carbon 14 in the 1.2-billion-year-old rocks besides the existence of life. This overlooks the possiiblity that carbon 14 might get into the rock in ways that don’t require life to have existed.

A
According to one dating technique, a few fossils of plants that lived on land are more than half a billion years old.
This provides additional evidence that life existed earlier than half a billion years ago.
B
The severity of conditions in the primordial oceans would have made it difficult for life to begin there.
This provides a reason to think life did not begin in the ocean.
C
Research suggests that some portions of the 1.2-billion-year-old rocks were at one time submerged in water, though other portions clearly never were.
This strengthens by establishing that some portions of the rocks were never under water. This helps to eliminate the possiblity that all of the carbon 14 in the rocks originated from undersea creatures.
D
The 1.2-billion-year-old rocks were formed from soil containing very small amounts of carbon 14 that entered the soil directly from the atmosphere.
This weakens the argument by providing an alternate source of the carbon 14 besides life. (D) suggests the carbon 14 in the rocks came directly from the atmosphere rather than from a living creature.
E
Uranium testing has been used to confirm that the age of the rocks is 1.2 billion years.
This strengthens the argument by confirming that the rocks originate from earlier than half a billion years ago. If this were not true, the argument would be less convincing.

Take PrepTest

Review Results

LSAT PrepTest 105 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Reading Comprehension

Section 4 - Logical Reasoning

Get full LSAT course

Leave a Reply