Passage 33
An influential early view held that ecosystems contain niches for a limited number of species and that competition for resources among species—whether native or nonnative invading ones—determines ecosystems’ species composition. However, factors other than competition often help explain invading species’ success. For example, the American grey squirrel, often cited as a classic example of competitively superior invading species, was introduced in England in 1876 and now thrives, while the native red squirrel population has declined. Although scientists have found gray squirrels to be more efficient foragers than red ones, they also note that even before the gray squirrel’s arrival, Britain’s red squirrel populations had a periodic tendency to die out, only to be subsequently reintroduced. Furthermore, many gray squirrels are silent carriers of a disease fatal to red squirrels.
1. It can be inferred that the author of the passage mentions the efficiency with which gray squirrels forage primarily in order to
A. identify a factor that explains a certain phenomenon
B. call attention to an inconsistency in a particular theory
C. suggest that competition cannot be the factor responsible for a particular outcome
D. acknowledge a fact that appears to support a view that the author intends to qualify
E. cite evidence that is not consistent with an early influential view about species competition
2. It can be inferred that the author of the passage would be most likely to agree with which of the following statements about the “early view?”
A. It reflects a mistaken assumption about the means by which nonnative species are introduced into ecosystems.
B. Its basic premise is shown to be valid by the effect of American gray squirrels on Britain’s red squirrel population.
C. It presents a simplistic picture of the means by which species composition within ecosystems is determined.
D. It can effectively explain the formation of ecosystems that contain few species but cannot adequately account for the formation of complex ecosystems.
E. It understates the importance of competition as a factor determining species composition within ecosystems.
答案：D C
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