passage 6 大象矮化

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先看题：

1. The primary purpose of the passage is to 主旨目的

2. According to the passage, which of the following statements about body size in mammals is true? 直接细节题，定位+同义改写，典型的定位失效题

文章讲解：

①During the Pleistocene epoch, several species of elephants isolated on islands underwent rapid dwarfing. ②This phenomenon was not necessarily confined to the Pleistocene, but may have occurred much earlier in the Southeastern Asian islands, although evidence is fragmentary. ③Several explanations are possible for this dwarfing. ④For example, islands often have not been colonized by large predators or are too small to hold viable predator populations. ⑤Once free from predation pressure, large body size is of little advantage to herbivores. ⑥Additionally, island habitats have limited food resources, a smaller body size and a need for fewer resources would thus be favored. ⑦Interestingly, the island rule is reversed for small mammals such as rodents, for which gigantism is favored under insular conditions.

①现象引入

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②继续描述现象，可以认为是作者观点

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③给出解释

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④ + ⑥ ↔ ⑦

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⑤

1. The primary purpose of the passage is to

A. question the plausibility of one explanation sometimes offered for the dwarfing of certain species living on islands 相反

B. argue that dwarfing of certain species living on islands occurred prior to the Pleistocene 无关，来自于②句的以偏概全。

C. cite evidence suggesting that dwarfing may have adverse consequences for some species living on islands 没有证据，解释现象，是找因不是找果，也可以认为是相反

D. present some possible explanations for the dwarfing of certain species living on islands 符合

E. contrast the effects of insular conditions on species with large body size and species with small body 无关/相反，现象解释，不是说明文

2. According to the passage, which of the following statements about body size in mammals is true? 直接细节题，定位+同义改写，典型的定位失效题

A. A large body is unfavorable to mammalian [剑1] species’ survival under most conditions. 没有证据

B. A large body tends to benefit small mammals living on islands. 符合

C. For most herbivorous mammals, a large body size is easier to sustain [剑2] in the absence of large predators. 相反，对应⑤

D. Under most conditions, a small body is less beneficial to herbivorous mammals than to nonherbivorous mammals. 没有证据

E. Among nonherbivorous mammals, a small body is more beneficial on anisland than on a mainland. 没有证据

 [剑1] [mæˈmeɪlɪən]

 [剑2]保持，维持