PrepTest 141, Section 4, Question 5
While biodiversity is indispensable to the survival of(38 more words not shown)
Which one of the following(10 more words not shown)
- ABiodiversity does not(8 more words not shown)
- BThere are various(14 more words not shown)
- CThe survival of(6 more words not shown)
- DThere are many(11 more words not shown)
- EThe species most(9 more words not shown)
Reading the argument
We need a variety of species. That doesn't mean we need to preserve every species for biodiversity to survive.
Think of an ecological niche as a role that needs someone to fill it. Imagine a particular kind of frog fills one of those roles, but another frog species could fill it too. Losing the first species wouldn't necessarily leave that role empty. That is the point of saying that many niches can be filled by more than one species.
Don't stretch that into 'Every species is replaceable.' We haven't been told that. The argument only needs some overlap to show that biodiversity doesn't require every currently existing species to remain. Widespread losses could still be a serious problem, and some species could have roles no other species can fill.
What we’re looking for
The question asks for the conclusion. Follow what explains what: the discussion of overlapping roles explains why biodiversity doesn't require every current species. The opening acknowledgment that biodiversity itself is indispensable sets up that distinction. The point is not that biodiversity is unnecessary; it's that preserving biodiversity and preserving every single species are different requirements.
Working the answers
- ACorrect
This states the distinction the argument supports: biodiversity doesn't require all currently existing species to survive. The overlapping niches give a reason for that claim. If another species can fill a particular role, losing one species needn't eliminate the role or destroy biodiversity.
- B
This supplies part of the explanation. Various ecological roles need to be filled. The argument then adds that more than one species can fill many of those roles, supporting the conclusion that biodiversity doesn't require every current species. B stops at the need for occupied niches.
- C
This is the opening acknowledgment. The author accepts that life depends on biodiversity and then explains why that doesn't require every species to continue existing. C captures what the author grants, but leaves out the distinction the rest of the argument establishes.
- D
This is the central reason for the conclusion. More than one species can fill many niches; therefore biodiversity doesn't require every existing species. D tells us why we should accept the conclusion, rather than stating the conclusion itself.
- E
Several species being able to fill one role doesn't mean one species fills several roles. Our hypothetical frog might share its ecological role with another species without also filling an entirely different niche. The argument never ranks species by indispensability or says the most indispensable ones fill multiple niches.
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