新gre考试实施以来,参加了新版gre考试的考生都觉得阅读部分的题难度增加了,这主要是由于新gre考试逻辑阅读需要考生的逻辑反应一定要比以前更快,可能考生还是有点不习惯,或是没有准备充足。那么,接下来的几天,小编将给大家搜索整理一些新gre考试逻辑阅读的练习题,希望考生能从平日的练习中总结规律,找到解题技巧。
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 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 hat bacterial chemosynthesis provides the foundation for hydrothermal-vent food chainsan exciting prospect because no other communities on Earth are independent of photosynthesis.
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