PrepTest 117, Section 3, Question 15
Seemingly inconsequential changes in sea temperature due to(52 more words not shown)
Which one of the following(17 more words not shown)
- AIt is a(11 more words not shown)
- BIt is intended(17 more words not shown)
- CIt helps show(9 more words not shown)
- DIt is offered(9 more words not shown)
- EIt is offered(14 more words not shown)
Reading the argument
A small temperature change can set off a much larger chain of effects.
At first, two degrees might not sound like much. But the passage says that rise stops seawater from mixing vertically. That matters because the mixing makes nutrients available to phytoplankton. Restrict those nutrients, and the trouble can move up the food chain.
Here is the next link: zooplankton eat phytoplankton, and zooplankton provide food for the rest of the chain. So a problem affecting the phytoplankton can reach animals that don't feed directly on those nutrients. The fish and seabirds need not be directly harmed by the warmer water for their food supply to be affected.
What we’re looking for
The question asks what the statement that zooplankton feed on phytoplankton does in the argument. Work back from the main point: small temperature changes eventually reduce fish and seabird populations. This feeding relationship helps explain how that happens. It is one link carrying the effect from restricted nutrients toward the larger animals, not a separate conclusion we're being asked to prove.
Working the answers
- A
The passage doesn't try to prove that zooplankton eat phytoplankton from the fact that phytoplankton use upwelling nutrients. Knowing what phytoplankton consume wouldn't by itself tell us what consumes them. The targeted statement is supplied as part of the explanation, rather than as a hypothesis supported by that earlier fact.
- B
The statement doesn't describe animals changing their feeding habits when the water stops mixing. It tells us the existing relationship: zooplankton eat phytoplankton. The concern is that this food supply is affected, which helps explain a decline farther up the food chain. Calling it an example of altered feeding habits misses its actual role.
- CCorrect
The feeding relationship helps connect the temperature change to larger sea animals indirectly. Less available nutrition affects phytoplankton; zooplankton rely on phytoplankton; other animals rely on zooplankton. The targeted statement supplies a link needed to follow that path. That is why it supports the claim about fish and seabird populations.
- D
The author describes a consequence of warming without making a recommendation to stop it. We might use the described harm in an argument for action, but the passage hasn't done that. D replaces the stated conclusion about population declines with a policy conclusion.
- E
All organisms goes well beyond the argument. We aren't told what happens to every land animal, plant, or other organism. The explanation concerns the chain leading to declines in fish and seabirds. It doesn't establish that every living thing is threatened, and that isn't the claim this premise is used to support.
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