PrepTest 125, Section 4, Question 11
Australia has considerably fewer species of carnivorous mammals(57 more words not shown)
Which one of the following(9 more words not shown)
- AAustralia has considerably(21 more words not shown)
- BIn ecosystems in(16 more words not shown)
- CThe unusual sparseness(25 more words not shown)
- DThe reason that(31 more words not shown)
- EBecause Australia's ecosystems(14 more words not shown)
Reading the argument
Why does Australia have fewer kinds of meat-eating mammals without a similar shortage of meat-eating reptile species? My first thought might be something about the climate. The author points us more specifically toward a shortage of food.
Given the food requirements we're told about, I can follow that explanation. A mammal that needs more food has a harder time in a sparse ecosystem than a reptile that needs less. That difference could help explain why Australia has fewer carnivorous mammal species than other continents while having about as many carnivorous reptile species.
What we’re looking for
For the main-conclusion question, separate the pattern from the explanation. The first sentence gives the pattern we're trying to explain. The discussion of food requirements supplies a reason to accept the proposed explanation. The main point sits between them: Australia's unusually sparse ecosystems probably account for the pattern. The final 'thus' gives a supporting step, not the argument's ultimate point.
Working the answers
- A
This gives the observation that prompted the explanation. We already know the species counts differ this way. The author is trying to tell us why, and A leaves out the proposed cause.
- B
This is the general disadvantage used to support the explanation. Animals that need more food are at a disadvantage where food is scarce. But the author's main point applies that idea to explain Australia's particular pattern of species. B stops before that explanation.
- CCorrect
The sparse ecosystems are probably why Australia differs from other continents in its number of carnivorous mammal species but not its number of carnivorous reptile species. That restates the proposed explanation. The food requirements tell us why the author thinks this explanation is plausible.
- D
This explains why mammals would be disadvantaged in a food-scarce environment. It connects their greater food needs with that disadvantage, which is useful support. But the argument goes further and uses that disadvantage to explain the distribution of species in Australia. D leaves out that final step.
- E
This gets us to Australia, but it still stops at the disadvantage. The main conclusion concerns why the numbers of species show the pattern described at the start. Mammals being disadvantaged is the mechanism offered to explain that pattern, not the full explanation the author wants us to accept.
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