LSAT 142 | Section 2 | Logical Reasoning: Q15

LR Question 15 Explanation

QUESTION TEXT: Often a type of organ or body structure is the only…

QUESTION TYPE: Complete the Argument

CONCLUSION: It’s not surprising that animals have separately evolved similar structures for similar tasks.

REASONING: It’s common for there only to be one efficient way to do a given task. So it’s not surprising that different species separately evolve the same structure. Animals have similar needs.

ANALYSIS: To complete the argument, you should carefully follow the reasoning of the argument.

The author gives a general argument about all organisms. Often, species will separately evolve similar structures because there’s only one way to do a given task.

The author then talks about animals. The only sensible way to end the argument is to apply the analogy to animals: since animals have similar needs, they’ll develop similar structures.

___________

1. The stimulus said nothing about what makes animals live in certain environments. This would be an odd way to end the argument.
2. CORRECT. This matches the evidence. The argument said that there’s often only one structure that meets a given set of needs. This conclusion extends that reasoning to animals: they have similar needs, so they will often develop similar adaptations.
3. The point of the argument is that organisms will develop similar adaptations in many situations. The argument wasn’t saying that organisms will manage to develop an adaptation for any need they have.
4. The argument didn’t say different species resemble each other. A giraffe’s eye is similar to our eye, but we don’t resemble giraffes.
5. Eyes and wings were just examples of unique structures. It would be ridiculous for the argument to say that all animals will adapt wings. Lots of animals don’t have wings! And some don’t have eyes either. This answer contradicts reality.