PrepTest 142, Section 1, Question 4
Scientist: Rattlesnakes prey on young California ground squirrels.(54 more words not shown)
Which one of the following,(9 more words not shown)
- ARattlesnakes do not(10 more words not shown)
- BSquirrels puff up(15 more words not shown)
- CRattlesnakes react much(21 more words not shown)
- DThe rattlesnake is(21 more words not shown)
- EMammals such as(11 more words not shown)
Reading the argument
Maybe the snake is reacting to the big, moving tail. How do we know the heat matters?
The squirrel puffs up its tail and wags it at the rattlesnake. Its tail also gets warmer. One possible explanation is that the warming comes along with the activity while the size or movement does the work of scaring the snake. In that case, heat would be a byproduct rather than part of the defense.
What we’re looking for
The rattlesnake's ability to detect heat makes the scientist's idea plausible, but detecting something isn't the same as being repelled by it. For a strengthener, I'd like a comparison: does the snake respond differently when the squirrel's tail is warm than when it isn't? That would help us see whether heat contributes to the reaction.
Working the answers
- A
We're interested in the squirrel's tail and the rattlesnake's response to it. Whether the snake can heat its own tail doesn't tell us what makes it retreat from a squirrel. This changes which animal is producing the heat.
- B
The same tail movement could serve different purposes in different settings. Using it to attract another squirrel's attention doesn't tell us whether heat contributes to repelling a rattlesnake. We still need information about the snake's response.
- CCorrect
This gives us the comparison we wanted: rattlesnakes react more defensively to squirrels with heated tails than to squirrels without them. That makes it more plausible that the heat contributes to the defensive effect instead of merely accompanying an effective movement. Notice the limited claim: heat plays a role. We don't have to establish that heat is the only thing that matters or that an unheated tail produces no reaction at all.
- D
Other predators might also provoke this behavior. But knowing when squirrels use a defense doesn't settle which feature of it affects rattlesnakes. The hypothesis concerns heat and this particular predator, and D never connects the two.
- E
The squirrel doesn't need to detect infrared energy itself for its heat to affect a snake that can detect it. This tells us about the wrong animal's sensing ability. The relevant question is how the rattlesnake responds to the squirrel's warm tail.
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