PrepTest 138, Section 3, Question 2
Forest fragmentation occurs when development severs a continuous(58 more words not shown)
Which one of the following(8 more words not shown)
- AWhite-footed mice are(6 more words not shown)
- BThe population density(15 more words not shown)
- CForest fragmentation reduces(12 more words not shown)
- DEfforts to stop(12 more words not shown)
- EDeer ticks reach(8 more words not shown)
Reading the argument
Breaking up a forest helps these mice. That doesn't necessarily make it good for us.
Picture a road cutting one large forest into smaller patches. White-footed mice thrive in those patches and reach their highest population densities there. That is a claim about some animals, including these mice. It doesn't tell us whether the whole ecosystem benefits.
Then we learn why the mice matter to people: they carry bacteria that cause Lyme disease, and deer ticks often pass those bacteria from mice to humans. Put the facts together. Conditions that favor dense populations of a major carrier could increase the opportunity for this harmful disease to reach people.
What we’re looking for
For a most-supported question, I'd look for that connection between forest fragmentation and human health. Keep it modest. We have a reason to be concerned about disease, not a guarantee that every fragmented forest causes an outbreak.
Working the answers
- A
Thriving in one setting doesn't mean being rare everywhere else. These mice could be common in an unfragmented forest and even more densely packed in small patches. The passage compares where their density is highest; it doesn't say they seldom live in continuous forests.
- B
We learn about some animals, with white-footed mice as the example. That doesn't establish what happens to most small-animal species. Other species might respond very differently to having their habitat broken up.
- C
This might sound like a reasonable environmental concern, but the passage doesn't describe a decline in the number or variety of species. It describes conditions in which certain mice thrive. We can't turn that limited observation into a conclusion about overall biodiversity.
- DCorrect
This expresses the health connection from the other direction: stopping fragmentation can benefit people. Preserving continuous forests could avoid conditions that favor dense populations of the mice that carry the disease-causing bacteria. That gives a basis for a possible health benefit. It doesn't mean stopping fragmentation would eliminate Lyme disease or that every such effort must improve health.
- E
The highest-density claim belongs to the mice. The ticks transmit bacteria, but we aren't told where ticks reach their highest population densities. More mice carrying bacteria could matter to disease transmission without establishing that these patches contain the densest tick populations. Don't transfer a fact about one animal to another.
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