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OFFICIAL47 According to paragraph 2, how did Charles Darwin contribute to the understanding of coral reefs?

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Coral Reefs
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An important environment that is more or less totally restricted to the intertropical zone is the coral reef. Coral reefs are found where the ocean water temperature is not less than 21 °C, where there is a firm substratum, and where the seawater is not rendered too dark by excessive amounts of river-borne sediment. They will not grow in very deep water, so a platform within 30 to 40 meters of the surface is a necessary prerequisite for their development. Their physical structure is dominated by the skeletons of corals, which are carnivorous animals living off zooplankton. However, in addition to corals there are enormous quantities of algae, some calcareous, which help to build the reefs. The size of reefs is variable. Some atolls are very large—Kwajelein in the Marshall Islands of the South Pacific is 120 kilometers long and as much as 24 kilometers across-but most are very much smaller, and rise only a few meters above the water. The 2,000-kilometer complex of reefs known as the Great Barrier Reef, which forms a gigantic natural breakwater off the northeast coast of Australia, is by far the greatest coral structure on Earth.

Coral reefs have fascinated scientists for almost 200 years, and some of the most pertinent observations of them were made in the 1830s by Charles Darwin on the voyage of the Beagle. He recognized that there were three major kinds: fringing reefs, barrier reefs, and atolls; and he saw that they were related to each other in a logical and gradational sequence. A fringing reef is one that lies close to the shore of some continent or island. Its surface forms an uneven and rather rough platform around the coast, about the level of low water, and its outer edge slopes downwards into the sea. Between the fringing reef and the land there is sometimes a small channel or lagoon. When the lagoon is wide and deep and the reef lies at some distance from the shore and rises from deep water it is called a barrier reef. An atoll is a reef in the form of a ring or horseshoe with a lagoon in the center.

Darwin s theory was that the succession from one coral reef type to another could be achieved by the upward growth of coral from a sinking platform, and that there would be a progression from a fringing reef, through the barrier reef stage until, with the disappearance through subsidence (sinking) of the central island, only a reef-enclosed lagoon or atoll would survive. A long time after Darwin put forward this theory, some deep boreholes were drilled in the Pacific atolls in the 1950s. The drill holes passed through more than a thousand meters of coral before reaching the rock substratum of the ocean floor, and indicated that the coral had been growing upward for tens of millions of years as Earth's crust subsided at a rate of between 15 and 51 meters per million years. Darwin s theory was therefore proved basically correct. There are some submarine islands called guyots and seamounts, in which subsidence associated with sea-floor spreading has been too speedy for coral growth to keep up.

Like mangrove swamps, coral reefs are extremely important habitats. Their diversity of coral genera is greatest in the warm waters of the Indian Ocean and the western Pacific. Indeed, they have been called the marine version of the tropical rain forest, rivaling their terrestrial counterparts in both richness of species and biological productivity. They also have significance because they provide coastal protection, opportunities for recreation, and are potential sources of substances like medicinal drugs. At present they are coming under a variety of threats, of which two of the most important are dredging and the effects of increased siltation brought about by accelerated erosion from neighboring land areas.

5.According to paragraph 2, how did Charles Darwin contribute to the understanding of coral reefs?

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【题目翻译】根据第2段,查尔斯·达尔文如何有助于理解珊瑚礁? A:他确定了珊瑚礁的主要类型,并解释了它们是如何联系在一起的。 B:他在一次科学航行中发现了珊瑚礁的存在。 C:他证明珊瑚礁大多位于离海岸很近的地方。 D:他看到珊瑚礁对于支持其他海洋生物的重要性。 【判定题型】:题目问的是文章中的具体细节信息,故根据题目问法可以判断本题为事实信息题。 【关键词定位】:根据关键词“Charles Darwin”,定位到Passage 2第1句,原句为“Coral reefs have fascinated scientists for almost 200 years, and some of the most pertinent observations of them were made in the 1830s by Charles Darwin on the voyage of the Beagle. ”,意思是“近200年来,珊瑚礁一直吸引着科学家,其中一些最相关的观测是在19世纪30年代由查尔斯·达尔文在比格尔号航行时进行的。”。 【逻辑分析】说明达尔文识别三种珊瑚礁并且解释了他们的相关性。 【选项分析】 A:他确定了珊瑚礁的主要类型,并解释了它们是如何联系在一起的。与文章相符,正确。 B:他在一次科学航行中发现了珊瑚礁的存在。不是发现珊瑚礁的存在,而是对珊瑚礁进行了观察。错误。 C:他证明珊瑚礁大多位于离海岸很近的地方。他发现岸礁生长于靠近大陆或岛屿的岸边,这只是其中一个发现。错误。 D:他看到珊瑚礁对于支持其他海洋生物的重要性。第二段没有提出。错误。

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