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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  24
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] Which of the following would most probably be regarded by the author as anomalous?
选项 A、A large primate species that eats mostly plants
B、A species of small mammals that is fiercely territorial
C、Two species of small primates that share the same territories
D、A species of small birds that is more abundant than many species of larger birds
E、A species of small rodents that requires more living space per individual than most species of larger rodents
答案 E
解析 Application
This question requires you to understand an underlying principle of the passage and to apply that principle to an instance that is not specifically discussed in the passage. The passage is concerned with how anomalous tamarins are: they are exceptions to the general rule that in general the number of animals in a species is proportional to the average body size of individuals within the species. The author also points out that tamarins are unusual in that the amount of space they require is out of proportion to their body size, suggesting the principle that an animal’s spatial requirement is generally proportional to the animal’s body size. And, though the passage is generally concerned with comparing tamarins to other primates, the author also compares tamarins’ spatial requirements to those of gray squirrels, a type of rodent.
A The author does not give any indication whether it would be anomalous for a species of large primates to eat mostly plants. The author does not present a general principle about the diets of primates, and says nothing specific about species of large primates.
B Although the author indicates that the "rigid" territoriality of tamarins is "rather exceptional among primates," the author lists several other primate species that are also territorial. The author does not indicate whether such territoriality is rare among small mammals in general.
C The author indicates that most primates do not have "such concerted territoriality" as tamarins do, suggesting that the author may not think that two other species of small primates sharing territories would be anomalous.
D Given that the author indicates that generally the number of individuals within a species is inversely proportional to the average body size of the members of the species, the author would probably expect that a species of small birds would be more abundant than most species of larger birds and would not regard this as anomalous
E Correct. The author would generally expect that smaller animals would require less living space than larger animals.
The correct answer is E.
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