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(See the complete passage discussion here: lsat/viewtopic.php?t=14508)
The correct answer choice is (E)
This is the most diffi cult question of the passage. In reviewing the question stem, you must read
carefully in order to note that you are weakening the author’s criticism of the supposed evolutionary
trend towards symbiosis. As you may recall, the author noted in lines 53-55, “Fungi both harmful
and benign can now be found both early and late in fungus evolutionary history, and that
consequently fungi can evolve towards symbiosis but then move just as easily back to parasitism.
You need to select some evidence that helps demonstrate that the overall trend, despite the author’s
evidence, is toward symbiosis (and, once there, does not move easily back to parasitism).
Answer choice (A): Since this information is entirely consistent with the assumption that fungi
evolve toward greater symbiosis, this response would not weaken the author’s critique.
Answer choice (B): The comparison of the fungi “family tree” to that of other organisms is entirely
irrelevant to the issue, and the relative complexity of the fungi evolutionary tree does not indicate
anything about the development of that tree.
Answer choice (C): Whether or not the DNA of symbiotic versus parasitic fungi is more diffi cult to
isolate is irrelevant to the correctness (or lack thereof) of the author’s conclusion that fungi do not
evolve towards symbiosis. You should not conclude that any relative diffi culties led to imprecision
and inaccuracy in research.
Answer choice (D): You should eliminate this response immediately, because its meaning is actually
consistent with the author’s criticism of the assumption in lines 50-55. If parasitic fungi sometimes
evolved much later than symbiotic fungi, that might help criticize an assumption that evolution
proceeds toward symbiosis.
Answer choice (E): This is the correct answer choice. The evolutionary assumption that parasitic
fungi evolve to become symbiotic so as not to destroy the host must be based on the idea that
fungi are more likely to survive in a symbiotic relationship. If it is true that fungus that return from
symbiosis to parasitism usually die out, that confi rms the basis of the evolutionary assumption, and
that would weaken the author’s critique. Furthermore, the answer states that fungi that turn back
toward parasitism usually become extinct fairly soon thereafter, suggesting that there really isn’t any
signifi cant evolution toward parasitism. The “regressive” branches can be seen as failed branches,
and you are expected to know that evolution doesn’t consist purely of promoting certain organisms—
it also consists of the extinction of others. If, as this answer choice states, “regressed” fungi quickly
die out, the temporary existence of regressed, parasitic fungi is irrelevant and the assumption that
evolution drives toward symbiosis may be valid.