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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  76
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 indicates that tamarin territories are
选项 A、surprisingly large
B、poorly situated
C、unusually abundant in food resources
D、incapable of supporting large troops of tamarins
E、larger in Peru than in other parts of South America
答案 A
解析 Supporting idea
This question depends on understanding what the passage says about tamarin territories. In the second paragraph, the passage claims that the most surprising thing about tamarins is the size of their territories, and it indicates how large these territories are by comparing them to the territories of certain other animals.
A Correct. The passage indicates that the size of tamarins’territories—large in comparison to the territories of several other species—is surprising.
B The passage gives no indication as to whether tamarin territories are poorly situated.
C Although the passage does discuss the tamarin diet, it does not indicate how abundant in food sources tamarin territories are.
D The passage does indicate that relatively few tamarins live per square kilometer, but it does not claim that this is so because the territories are incapable of supporting a larger number of tamarins. In fact, there is some suggestion that the territories would seem to be capable of supporting more, which is one reason the size of the territories is so surprising.
E The passage does not compare the size of tamarin territories in Peru to tamarin territories elsewhere in South America.
The correct answer is A.
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