PrepTest 120, Section 4, Question 2
Dr. Theresa Pagano, a biologist, has found that(61 more words not shown)
Each of the following, if(6 more words not shown)
- ACheckerspot butterfly colonies(11 more words not shown)
- BClimate does not(16 more words not shown)
- CExperimental evidence suggests(16 more words not shown)
- DIn recent years,(13 more words not shown)
- ESeveral studies have(18 more words not shown)
Reading the argument
The butterflies are moving north, and the warmer zones are moving north with them. Climate looks like a reasonable explanation. But what else might be changing? Predators, human development, or even the way researchers count butterflies could also affect where we find them.
The close match gives Dr. Pagano a reason to investigate temperature. It doesn't settle the cause on its own. I'd want evidence that warmth matters to these butterflies. Are they sensitive to temperature changes? Have temperature changes affected their populations before?
What we’re looking for
This is a strengthen EXCEPT question. Four choices will help the climate explanation; we want the one that doesn't. It needn't disprove the explanation. It can simply fail to make that explanation more convincing.
Working the answers
- A
This helps. Small temperature changes have substantial effects on checkerspot colonies in a laboratory. That gives us a reason to expect changes in climate to matter outside the laboratory too. It doesn't prove what caused the geographic shift, but it supports treating temperature as a relevant influence.
- B
This also helps, even though the first part says climate doesn't affect the butterflies directly. Follow the food: the butterflies depend on plants, and those plants thrive in warmth. As the warm zones shift, the plants could shift, and the butterflies could follow. Climate can affect the butterflies through their food supply without acting on the butterflies directly.
- CCorrect
If these butterflies readily adapt to many temperatures and geographic conditions, we haven't been given a reason they would have to follow the warm zones. They could potentially remain where they are and adapt. That doesn't prove climate had nothing to do with the movement; butterflies might move for climate-related reasons even when they could survive elsewhere. But unlike the other choices, C doesn't supply evidence supporting the proposed explanation.
- D
This helps by giving us another observed connection between temperature and checkerspot numbers. Lower temperatures have accompanied population reductions. That makes an explanation involving suitable temperatures more plausible, even though another correlation still isn't proof of the cause.
- E
These aren't checkerspots, so the evidence is less direct. Still, closely related butterflies needing warm climates gives us some reason to think warmth could matter to checkerspots too. A strengthener can provide suggestive evidence without proving that every related species has exactly the same needs.
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