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  3. For most species of animals, the number of individuals in the species is inverse

For most species of animals, the number of individuals in the species is inverse

游客2024-01-12  20
问题 For most species of animals, the number of individuals in the species is inversely proportional to the average body size for members of the species: the smaller the body size, the larger the number of individual animals. The tamarin, a small South American monkey, breaks this rule. Of the ten primate species studied in Peru’s Manu National Park, for example, the two species of tamarins, saddle-backed and emperor, are the eighth and ninth least abundant, respectively. Only the pygmy marmoset, which is even smaller, is less abundant. The tamarin’s scarcity is not easily explained; it cannot be dismissed as a consequence of diet, because tamarins feed on the same mixture of fruit, nectar, and small prey as do several of their more numerous larger counterparts, including the two capuchins known as the squirrel monkey and the night monkey. Although the relative proportions of fruits consumed varies somewhat among species, it is hard to imagine that such subtle differences are crucial to understanding the relative rarity of tamarins.
To emphasize just how anomalously rare tamarins are, we can compare them to the other omnivorous primates in the community. In terms of numbers of individuals per square kilometer, they rank well below the two capuchins, the squirrel monkey and the night monkey. And in terms of biomass, or the total weight of the individuals that occupy a unit area of habitat, each tamarin species is present at only one-twentieth the mass of brown capuchins or one-tenth that of squirrel monkeys. To gain another perspective, consider the spatial requirements of tamarins. Tamarins are rigidly territorial, vigorously expelling any intruders that may stray within the sharply defined boundaries of their domains. Groups invest an appreciable part of their time and energy in patrolling their territorial boundaries, announcing their presence to their neighbors with shrill, sweeping cries. Such concerted territoriality is rather exceptional among primates, though the gibbons and siamangs of Asia show it, as do a few other New World species such as the titi and night monkeys. What is most surprising about tamarin territories is their size.
Titi monkeys routinely live within territories of 6 to 8 hectares, and night monkeys seldom defend more than 10 hectares, but tamarin groups routinely occupy areas of 30 to 120 hectares. Contrast this with the 1 to 2 hectares needed by the common North American gray squirrel, a nonterritorial mammal of about the same size. A group of tamarins uses about as much space as a troop of brown capuchins, though the latter weighs 15 times as much. Thus, in addition to being rare, tamarins require an amount of space that seems completely out of proportion to their size. [br] The author most probably regards the tamarins studied in Manu National Park as
选项 A、an endangered species
B、typical tamarins
C、unusually docile
D、the most unusual primates anywhere
E、too small a sample to be significant
答案 B
解析 Inference
This question requires you to make an inference from what the author says about the tamarins studied in Manu National Park to a claim about how the author most likely regards these tamarins. The author considers certain information that has been gathered about the two tamarin species studied in the park, and on the basis of that, makes claims about tamarins in general (note that the author elsewhere in the passage simply refers to "tamarins" without qualification, i.e., without referring specifically to "the tamarins studied in Manu National Park’’). This suggests that the author would regard the tamarins studied in the park as being typical of tamarins generally, at least in the ways discussed.
A It is possible that the two tamarin species studied in the park are endangered, but apart from noting the surprisingly small number of individuals belonging to the species, there is no information that would suggest that they are endangered, and the mere fact that the number of members is relatively small compared to the number of members in other species is not sufficient to indicate that they are endangered, as that number could nonetheless be stable or even growing.
B Correct. The author does not specifically mention anything that would indicate that these tamarins are atypical of tamarins in general, and appears to make inferences about tamarins in general on the basis of the two species studied in the park. The author would not be justified in making such inferences if the author believed that the tamarins observed in the park were not in fact typical.
C The author does not give any indication that these species are unusually docile, and in fact suggests the opposite by indicating that tamarins vigorously expel any intruders from their territories.
D The author does note some ways in which these tamarin species are unusual among primates, but does not indicate that they are "the most unusual primates anywhere."The author, in fact, indicates that in one of the ways that these species are unusual—their relative scarcity despite their small body size—another primate species, the pygmy marmoset, is even more unusual.
E Because the author appears to make some inferences from information about the tamarins studied in the park to claims about tamarins in general, the author does not seem to regard the tamarins studied in the park as too small a sample to be significant.
The correct answer is B.
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