PrepTest 116, Section 3, Question 17
If one of the effects of a genetic(64 more words not shown)
If the statements above are(9 more words not shown)
- AA species possesses(13 more words not shown)
- BAll the effects(12 more words not shown)
- CA species possesses(8 more words not shown)
- DA genetic mutation(11 more words not shown)
- EA genetic mutation(13 more words not shown)
Reading the argument
A longer neck might help a giraffe reach more leaves. If that helped the species survive, it could give us the sort of benefit this passage requires. But we need to consider what else comes with the change.
Imagine the same mutation also created a risk of serious illness late in the giraffe's life. Perhaps the feeding advantage would still be worthwhile, especially if the giraffe had already reproduced before becoming ill. Change the example so the mutation makes the giraffe die very young, and that cost could wipe out the longer neck's benefit. These are imagined examples to make the rule concrete, not claims about giraffe biology.
The passage allows negative traits to come along with a helpful one. It just says those negatives must not cancel the benefit. So don't treat any downside as an automatic disqualification.
What we’re looking for
Now notice the task: each answer could be true except one. We need the statement that conflicts with the rules, not a statement we can prove. Something can be unsupported and still be possible. Keep both requirements in view: a favored mutation needs a substantial survival benefit, and its accompanying costs can't erase that benefit.
Working the answers
- A
A species could possess a trait with only neutral effects. A doesn't say that natural selection favors that trait, and the passage doesn't say every trait a species possesses must be favored. Merely having a neutral trait doesn't violate the stated condition for being favored.
- B
A mutation could have only beneficial effects. The passage allows accompanying negative effects but doesn't require them. If every effect made a substantial contribution to survival, there would be no conflict with the rule.
- C
A harmful trait could be carried along with a beneficial one. That is exactly the possibility the second sentence discusses. For example, the imagined illness risk could reduce survival potential while the longer neck supplied a larger advantage. C doesn't say the harmful trait wipes out every accompanying benefit.
- D
Several negative traits aren't necessarily a greater cost than one positive trait is a benefit. Suppose the longer neck comes with a few minor problems involving the giraffe's teeth or eyes. Those problems could still be outweighed by the feeding advantage.
Count is not severity. D tells us there are several negatives, not that they cancel the substantial benefit. That leaves room for the mutation to be favored under the passage's rule.
- ECorrect
All neutral means no substantial contribution to survival. But the first sentence says a mutation is favored only if at least one effect makes that contribution. E therefore violates a required condition.
Unlike A, E doesn't merely say a neutral trait exists. It says a wholly neutral mutation is favored. That extra claim creates the contradiction. We don't need to calculate any negative side effects here; E already fails the benefit requirement.
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