PrepTest 118, Section 2, Question 19
A lichen consists of a fungus living in(450 more words not shown)
Which one of the following,(17 more words not shown)
- AEvolutionary theorists now(13 more words not shown)
- BThe evolutionary tree(14 more words not shown)
- CThe DNA of(19 more words not shown)
- DThe placement of(24 more words not shown)
- EBranches of the(15 more words not shown)
Reading the passage
First, get the direction straight. The old assumption says parasitic relationships generally become more benign and eventually symbiotic. The writer challenges that assumption because the new family tree suggests fungi can go back from symbiosis to parasitism.
What we’re looking for
We're weakening the writer's criticism, so we need something that helps the old assumption survive. Maybe the research is unreliable, or maybe the apparent reversals don't tell us as much as the writer thinks. I don't yet have one particular fact to predict; I'll check what each answer does to that challenge.
Working the answers
- A
This supports the direction the writer uses to challenge the old assumption: symbiosis toward parasitism. It's relevant, but it helps the criticism we need to weaken.
- B
A more complex family tree doesn't tell us which way relationships tend to evolve. Complexity alone doesn't undermine the new findings.
- C
Difficulty isolating DNA was the problem the new tools overcame. C doesn't establish that those tools failed or that the researchers analyzed the wrong DNA.
- D
At first, a fact being hidden by the old classification might sound like a reason to doubt the research. But read the fact: parasitic fungi sometimes evolved later than symbiotic ones. That doesn't show evolution tending toward symbiosis. And the misleading classification was the old one, which the new research has revised. D doesn't give us a reason to discount the writer's challenge.
- ECorrect
This changes how much the apparent reversals establish. If branches that turn toward parasitism usually die out soon afterward, those reversals tend to be evolutionary dead ends. They provide less reason to reject a general, lasting trend toward symbiosis among surviving branches.
E doesn't say that the reversal never happens, and dying out afterward doesn't mean that no evolution occurred. The point is that the reversed direction usually doesn't last. That's enough to weaken the writer's use of those reversals against the general assumption.
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