托福阅读否定事实信息题是阅读考试十大题型之一，通常每篇阅读中都会出现;tpo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阅读中考察的否定事实信息题及其对应的解析，供大家参考使用。本文带来的是TPO17-3的否定事实信息题，一起来看看吧。
TPO17-3 Symbiotic Relationships
Paragraph 3
At times, it is actually possible to watch the effects of natural selection in host-parasite relationships. For example, Australia during the 1940 s was overrun by hundreds of millions of European rabbits. ■The rabbits destroyed huge expanses of Australia and threatened the sheep and cattle industries. In ■1950, myxoma virus, a parasite that affects rabbits, was deliberately introduced into Australia to control the rabbit population. ■Spread rapidly by mosquitoes, the virus devastated the rabbit population. ■The virus was less deadly to the offspring of surviving rabbits, however, and it caused less and less harm over the years. Apparently, genotypes (the genetic make-up of an organism) in the rabbit population were selected that were better able to resist the parasite. Meanwhile, the deadliest strains of the virus perished with their hosts as natural selection favored strains that could infect hosts but not kill them. Thus, natural selection stabilized this host-parasite relationship.
6. According to paragraph 3. all of the following characterize the wav natural selection stabilized the Australian rabbit population EXCEPT:
The most toxic viruses died with their hosts.
The suiviving rabbits were increasingly immune to the virus.
The decline of the mosquito population caused the spread of the virus to decline.
Rabbits with specific genetic make-ups were favored
解析：EXCEPT题，排除法，A的most toxic viruses做关键词定位至倒数第二句的deadliest strains of the virus，所以A正确，不选;B的surviving rabbits做关键词定位至倒数第四句，正确，不选;C的mosquito population做关键词定位至第五句，跟选项说的完全无关，所以C错，选;D的genetic make-up做关键词定位至倒数第三句，所以D正确，不选
[3]有时候，寄生关系的自然选择效应也可能在现实中被观察到。比如说，二十世纪四十年代，亿万只欧洲兔在澳大利亚泛滥成灾。兔子肆虐了广袤的土地，并给牛羊业带来了极大的威胁。1950年，为了控制兔灾，澳大利亚特意引进了一种名为粘液瘤病毒的可影响兔子的寄生虫。通过蚊子的快速传播，兔子数量急剧减少。然而，这种寄生虫对于生存下来的兔群的后代就没有那么致命了，而且这种伤害逐年减小。显然，该兔群的遗传性状(生物体的基因结构)经过了自然选择，已经具备了更好地抵抗粘液瘤病毒的能力。同时，由于自然选择更倾向于那些能够感染寄主但不致其死的品系，这种病毒最致命的品系也逐渐地衰败了。这样，自然选择便使得寄主-寄生虫的关系趋于稳定。
Paragraph 5
The third type of symbiosis, mutualism, benefits both partners in the relationship Legume plants and their nitrogen-fixing bacteria, and the interactions between flowering plants and their pollinators, are examples of mutualistic association. In the first case, the plants provide the bacteria with carbohydrates and other organic compounds, and the bacteria have enzymes that act as catalysts that eventually add nitrogen to the soil, enriching it. In the second case, pollinators (insects, birds) obtain food from the flowering plant, and the plant has its pollen distributed and seeds dispersed much more efficiently than they would be if they were carried by the wind only. Another example of mutualism would be the bull's horn acacia tree, which grows in Central and South America. The tree provides a place to live for ants of the genus Pseudomyrmex. The ants live in large, hollow thorns and eat sugar secreted by the tree. The ants also eat yellow structures at the tip of leaflets: these are protein rich and seem to have no function for the tree except to attract ants. The ants benefit the host tree by attacking virtually anything that touches it. They sting other insects and large herbivores (animals that eat only plants) and even clip surrounding vegetation that grows near the tree. When the ants are removed, the trees usually die, probably because herbivores damage them so much that they are unable to compete with surrounding vegetation for light and growing space.
10. According to paragraph 5, which of the following is NOT true of the relationship between the bull s horn acacia tree and the Pseudomyrmex ants?
Ants defend the host trees against the predatory actions of insects and animals.
The acacia trees are a valuable source of nutrition for the ants.
The ants enable the acacia tree to produce its own chemical defenses.
The ants protect the acacia from having to compete with surrounding vegetation
解析：EXCEPT题，排除法，A的predatory actions和insects and animals做关键词定位至倒数第二句，所以A正确，不选;B的nutrition 做关键词定位至倒数第四句的protein rich，正确，不选;C的chemical defenses在原文没有对应点 C错，选;D的surrounding vegetation 做关键词定位至最后一句，所以D正确，不选
[5]第三种关系，互利共生，是指共生双方能够互利互惠。其中典型的例子有豆科植物和固氮细菌，以及开花植物和授粉生物。在第一个例子中，植物可以为细菌提供碳水化合物以及其他一些化合物，而这些细菌则能产生一种起催化作用的酶，它最终增加土壤中的氮元素来丰富土壤。在第二个例子中，授粉生物(昆虫、鸟类等)从开花植物中获取食物，而植物则可以通过它们来传递花粉和种子，这比仅仅依靠风来传递要高效得多。还有一个互利共生的例子是生长在美国中南部的牛角金合欢树。这种树为一种伪蚁属的蚂蚁提供了栖居地。这些蚂蚁住在大的中空的荆棘丛中，汲取金合欢树分泌出来的糖分。它们还吃树叶末端的黄色组织：这个部分富含蛋白质，但是除了吸引蚂蚁，似乎对树本身没有任何功能。而这些蚂蚁们则可以帮助它们的寄主攻击外界几乎所有的威胁。它们会叮咬昆虫和食草动物(只以植物为食的动物)，甚至可以削减生长在树周围的其他植物。一旦蚂蚁被清除掉，这种树就难以存活，很可能是因为它们被食草动物损害而无力与周围的其他植物争夺阳光和生长空间。
以上就是托福阅读TPO17-3中的否定事实信息题及其解析，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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