托福阅读修辞目的题是阅读考试中比较常见的一种题型，tpo则是托福阅读备考最权威的材料，所以托福小编综合二者，为大家集中整理了tpo阅读中考察的修辞目的题及其对应的解析，供大家参考使用。本文带来的是TPO29-2的修辞目的题，一起来看看吧。
TPO29-2 Competition
Paragraph 2: No serious competition exists when the major needed resource is in superabundant supply, as in most cases of the coexistence of herbivores (plant eaters). Furthermore, most species do not depend entirely on a single resource, if the major resource for a species becomes scarce, the species can usually shift to alternative resources. If more than one species is competing for a scarce resource, the competing species usually switch to different alternative resources. Competition is usually most severe among close relatives with similar demands on the environment. But it may also occur among totally unrelated forms that compete for the same resource, such as seed-eating rodents and ants. The effects of such competition are graphically demonstrated when all the animals or all the plants in an ecosystem come into competition, as happened 2 million years ago at the end of Pliocene, when North and South America became joined by the Isthmus of Panama. North and South American species migrating across the Isthmus now came into competition with each other. The result was the extermination of a large fraction of the South American mammals, which were apparently unable to withstand the competition from invading North American species----although added predation was also an important factor.
7.In paragraph 2, why does the author talk about what happened as a result of North and South America becoming joined at the Isthmus of Panama?
O To make the point that predation can have as much effect on species survival as competition does
O To show how the ability to switch to an alternative resource can give a species a competitive advantage
O To account for the current species composition of North and South America
O To provide an example of the serious effects of competition between unrelated species
解析：引出南北美洲物种竞争结果的主句是“The effects of such competition are graphically demonstrated…”由此推断，南北美洲动物竞争的结果就是为了说明竞争的Effects。因此选择D。A原文提到了，在最后的半句，但是前面的although说明了这不是主要观点。
[2] 当主要需求的资源能充分供给时，竞争就不会很激烈，正如很多情况下植食动物都能够共存。而且绝大部分物种并不只依靠一种资源，当某物种的主要资源匮乏时，它们常转向其它候选资源。如果多个物种竞争同一稀缺资源，他们常会转向不同的候选资源。近亲之间的竞争往往最激烈，因为他们对环境有相似需求。但激烈竞争也可能发生在毫不相关却需要同一资源的物种之间，例如吃种子的啮齿动物和蚂蚁。当一个生态系统中的所有动植物都参与到竞争中来时竞争的影响将表现得淋漓尽致，比如在两百万年前上新世末期当南、北美洲在巴拿马地峡处聚拢时所发生的一切。南、北美洲的物种可以穿越地峡而相互竞争。结果是大量南美洲哺乳动物因抵抗不了来自北美洲物种的竞争而灭绝----尽管过度捕杀也是一个很重要的因素。
以上就是托福阅读TPO29-2中的修辞目的题及其解析，大家可以在备考的时候参考复习，希望能够帮助大家的考前准备。最后前程百利祝大家都能取得理想的托福考试成绩。
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