[问答] 一道老G的题求助 [复制链接]

阿甘-w
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电梯直达

楼主

发表于 2016-3-9 10:56:56 |只看该作者 |倒序浏览

NO.8的题
The deep sea typically has a sparse fauna dominated by tiny worms and crustaceans, with an even sparser distribution of larger animals. However, near hydrothermal vents, areas of the ocean where warm water emerges from subterranean sources, live remarkable densities of huge clams, blind crabs, and fish.
Most deep-sea faunas rely for food on particulate matter, ultimately derived from photosynthesis, falling from above. The food supplies necessary to sustain the large vent communities, however, must be many times the ordinary fallout. The first reports describing vent faunas proposed two possible sources of nutrition: bacterial chemosynthesis, production of food by bacteria using energy derived from chemical changes, and advection, the drifting of food materials from surrounding regions. Later, evidence in support of the idea of intense local chemosynthesis was accumulated: hydrogen sulfide was found in vent water; many vent-site bacteria were found to be capable of chemosynthesis; and extremely large concentrations of bacteria were found in samples of vent water thought to be pure. This final observation seemed decisive. If such astonishing concentrations of bacteria were typical of vent outflow, then food within the vent would dwarf any contribution from advection. Hence, the widely quoted conclusion was reached that bacterial chemosynthesis provides the foundation for hydrothermal-vent food chains—an exciting prospect because no other communities on Earth are independent of photosynthesis.
There are, however, certain difficulties with this interpretation. For example, some of the large sedentary organisms associated with vents are also found at ordinary deep-sea temperatures many meters from the nearest hydrothermal sources. This suggests that bacterial chemosynthesis is not a sufficient source of nutrition for these creatures. Another difficulty is that similarly dense populations of large deep-sea animals have been found in the proximity of “smokers”—vents where water emerges at temperatures up to 350℃. No bacteria can survive such heat, and no bacteria were found there. Unless smokers are consistently located near more hospitable warm-water vents, chemosynthesis can account for only a fraction of the vent faunas. It is conceivable, however, that these large, sedentary organisms do in fact feed on bacteria that grow in warm-water vents, rise in the vent water, and then rain in peripheral areas to nourish animals living some distance from the warm-water vents.
Nonetheless advection is a more likely alternative food source. Research has demonstrated that advective flow, which originates near the surface of the ocean where suspended particulate matter accumulates, transports some of that matter and water to the vents. Estimates suggest that for every cubic meter of vent discharge, 350 milligrams of particulate organic material would be advected into the vent area. Thus, for an average-sized vent, advection could provide more than 30 kilograms of potential food per day. In addition, it is likely that small live animals in the advected water might be killed or stunned by thermal and/or chemical shock, thereby contributing to the food supply of vents.
题目：19.Which of the following does the author cite as a weakness in the argument that bacterial chemosynthesis provides the foundation for the food chains at deep-sea vents?
(A) Vents are colonized by some of the same animals found in other areas of the ocean floor.
(B) Vent water does not contain sufficient quantities of hydrogen sulfide.
(C) Bacteria cannot produce large quantities of food quickly enough.
(D) Large concentrations of minerals are found in vent water.
(E) Some bacteria found in the vents are incapable of chemosynthesis.
这道题新g里改成了选句子
我选的C，但是答案是A。A的定位在哪知道，但是为什么C不对

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阿甘-w
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沙发

发表于 2016-3-9 11:39:09 |只看该作者

顶顶顶求回答啊啊啊

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qwhrp94
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板凳

发表于 2016-3-9 12:59:35 |只看该作者

我们看到题目的问题是作者引用了什么样的证据来说明bacterial chemosynthesis（BC）作为食物链的理论是错误的。所以我们首先注意到这样两句话：
Hence, the widely quoted conclusion was reached that bacterial chemosynthesis provides the foundation for hydrothermal-vent food chains—an exciting prospect because no other communities on Earth are independent of photosynthesis.
There are, however, certain difficulties with this interpretation.
即普遍的结论是BC是作为食物供给的来源，但是作者提出了反驳，即这种解释有一些difficulties。
然后作者开始就自己的观点提出证据，这就是题目的关键了：
For example, some of the large sedentary organisms associated with vents are also found at ordinary deep-sea temperatures many meters from the nearest hydrothermal sources.
一些与vents相联系的large sedentary organisms 也在其他地方找到了，转述一下也就是答案了。

至于C，我猜测LZ是看了This suggests that bacterial chemosynthesis is not a sufficient source of nutrition for these creatures这句话。但是这里的sufficient 不能简单的理解成BC的数量，而应该理解成种类。文中提到interpretation之所以是excited的，是因为它的结论使得文中提到的生物成为唯一不用光合作用的生物。然而事实上BC可能不是唯一的能量来源，因此这里的sufficient更倾向于解释为除了BC还有其他种类的来源，包括光合作用可能也在内。
不知道这样说能不能理解了？

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