求助：36套 Ex11第6题

米兰的拿铁 · 发表于 2013-4-15 09:58:40

答案解释是：”定位在 L9“The food supplies necessary to sustain the large vent communities” By Desperado“ 但我觉得这个还是解释不通。第一，这个没有解释答案的"smaller than many vent faunas"，L9的意思其实没有和这个选项有很大联系；第二文中第一段第一句有提到”dominated by tiny worms and....."这个倒是有关联，而且第二段第一句最后一词“from above”也呼应了上段，但是个人感觉这个和选出B还是有点牵强。

求大神讲解

米兰的拿铁 · 发表于 2013-4-15 17:53:19

添个原文：

The deep sea typically has a sparse fauna dominated by tiny worms and crustaceans, with an even sparser distribution of larger animals. However, near
Line hydrothermal vents, areas of the ocean where warm water 5 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 10 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
15 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
20 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.
25 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.
30 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
35 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°C. No bacteria can survive such
40 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
45 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
50 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
55 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
60 shock, thereby contributing to the food supply of vents. (479 words)

米兰的拿铁 · 发表于 2013-4-15 17:54:13

问题：
6. The information in the passage suggests that the majority of deep-sea faunas that live in nonvent habitats have which of the following characteristics?
(A) They do not normally feed on particles of food in the water.
(B) They are smaller than many vent faunas.
(C) They are predators.
(D) They derive nutrition from a chemosynthetic
food source.
(E) They congregate around a single main food
source.

kenny8tb · 发表于 2013-4-15 18:48:56

定位至原文：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 (hydrothermal: adj.热水的, 热液的) vents, areas of the ocean where warm water emerges from subterranean sources, live remarkable densities of huge clams, blind crabs, and fish.

米兰的拿铁 · 发表于 2013-4-15 19:25:14

kenny8tb 发表于 2013-4-15 18:48
定位至原文：The deep sea typically has a sparse fauna dominated by tiny worms and crustaceans, with ...

原来要整段看啊，大谢哈

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