2018年5月5日SAT阅读真题及解析3

>>SAT真题回忆：2018年5月5日SAT阅读真题及解析3

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SAT阅读真题原文3之自然科学类

broad bean是否会通过fungal hyphae 来传达信息从而吸引wasp而抵制另一种危害性的虫子叫a什么鬼。通过做实验证明了这一结论。

Passage 3: Beans Talk, Natural Science

THE idea that plants have developed a subterranean internet, which they use to raise the alarm when danger threatens, sounds more like the science-fiction of James Cameron’s film “Avatar” than any sort of science fact. But fact it seems to be, if work by David Johnson of the University of Aberdeen is anything to go by. For Dr Johnson believes he has shown that just such an internet, with fungal hyphae standing in for local Wi-Fi, alerts beanstalks to danger if one of their neighbors is attacked by aphids.

Dr Johnson knew from his own past work that when broad-bean plants are attacked by aphids they respond with volatile chemicals that both irritate the parasites and attract aphid-hunting wasps. He did not know, though, whether the message could spread, tomato-like, from plant to plant. So he set out to find out—and to do so in a way which would show if fungi were the messengers.

As they report in Ecology Letters, he and his colleagues set up eight “mesocosms”, each containing five beanstalks. The plants were allowed to grow for four months, and during this time every plant could interact with symbiotic fungi in the soil.

Not all of the beanstalks, though, had the same relationship with the fungi. In each mesocosm, one plant was surrounded by a mesh penetrated by holes half a micron across. Gaps that size are too small for either roots or hyphae to penetrate, but they do permit the passage of water and dissolved chemicals. Two plants were surrounded with a 40-micron mesh. This can be penetrated by hyphae but not by roots. The two remaining plants, one of which was at the center of the array, were left to grow unimpeded.

Five weeks after the experiment began, all the plants were covered by bags that allowed carbon dioxide, oxygen and water vapor in and out, but stopped the passage of larger molecules, of the sort a beanstalk might use for signaling. Then, four days from the end, one of the 40-micron meshes in each mesocosm was rotated to sever any hyphae that had penetrated it, and the central plant was then infested with aphids.

At the end of the experiment Dr Johnson and his team collected the air inside the bags, extracted any volatile chemicals in it by absorbing them into a special porous polymer, and tested those chemicals on both aphids (using the winged, rather than the wingless morphs) and wasps. Each insect was placed for five minutes in an apparatus that had two chambers, one of which contained a sample of the volatiles and the other an odorless control.

The researchers found, as they expected from their previous work, that when the volatiles came from an infested plant, wasps spent an average of 3½ minutes in the chamber containing them and 1½ in the other chamber. Aphids, conversely, spent 1¾ minutes in the volatiles’ chamber and 3¼ in the control. In other words, the volatiles from an infested plant attract wasps and repel aphids.

Crucially, the team got the same result in the case of uninfected plants that had been in uninterrupted hyphae contact with the infested one, but had had root contact blocked. If both hyphae and roots had been blocked throughout the experiment, though, the volatiles from uninfected plants actually attracted aphids (they spent 3½ minutes in the volatiles’ chamber), while the wasps were indifferent. The same pertained for the odor of uninfected plants whose hyphae connections had been allowed to develop, and then severed by the rotation of the mesh.

Broad beans, then, really do seem to be using their fungal symbionts as a communications network, warning their neighbors to take evasive action. Such a general response no doubt helps the plant first attacked by attracting yet more wasps to the area, and it helps the fungal messengers by preserving their leguminous hosts.

SAT阅读真题解读3之自然科学类

来自于2013年economist newspaper的beans’talk。现象解释性文章。第 一段首先列出了一个现象“植物可能是相互联系的”：当一个植物收到攻击或者影响，就会像其他植物发出报警信号，就像local Wi-Fi 一样，那么有一个理论被提出，是不是当有蚜虫攻击植物，植物就会通过一些 fungi 去给邻居植物发出信号呢。之后研究小组展开实验，分为8个小组，每个实验小组有5株植物，然后对于不同的植物进行不同的变量控制。实验结果显示，在根接触不到的情况下，每株植物都能通过hyphae来传递信息，当一株植物被蚜虫攻击的时候，这株植物都会释放化学物质驱赶蚜虫，吸引蚜虫的predator大黄蜂。而hyphae无法透出来的植物们，即使有的被蚜虫袭击，其他也不会释放这种物质。

题目：

第 一题：文章目的题，问整篇文章的 purpose，其中正确答案应该理论通过实验去论证，有干扰项 undermine了一个理论等。

第二题：段落作用，考察第 一段为后面引出讨论起到了什么样的作用，其中迷惑选项有无中生有信息例如 parasite interaction 等，答案应该为将现象生活化，后面进行科学讨论和研究。

第三题：细节题，考察作者在研究菌类和植物的关系，基于了哪些 old fact?答案应该出自信息 line 10，讲到过去的研究表明植物可以释放 volatile chemical。

第四题：细节题，问文章中调查人员做的实验的实验目的是什么?根据文章行号line15 部分，可以看到有同义词对应，本次试验 set out 等，为了证明细菌等是否是被攻击信息的传播者。

第五题：询证题，同上题。

第六题：段落作用题，问第三四段的段落作用是什么， 解题应该更好理解三四段段落大意，明晰在整个实验中的作用，三四段重点讲解的是：试验把植物分为几组，并且各自控制何种变量，答案应为 experiment condition。

第七题：词汇题考察 control 的语境含义，文章内容为两种植物，one感染细菌，the other odorless control，选项有 force;restrictive mechanism等。

第八题：细节题，问实验中能够解释为被感染细菌的植物吸引蚜虫的原因，解题需要定位到倒数第二段，讲解第二种实验结果的部分。

第九题：观点总结，题目问，通过文章能够总结出 bean 和 fungi 之间的关系，定位到最后一段讲解双方关系，其中有两help可以帮助解题，答案选项有 mutual beneficial.

第十题：询证题同上一题。

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