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  3. There are both great similarities and considerable diversity in the ecosyste

There are both great similarities and considerable diversity in the ecosyste

游客2025-01-19  23
问题     There are both great similarities and considerable diversity in the ecosystems that evolved on the islands of Oceania in and around the Pacific Ocean. The islands, such as New Zealand, that were originally parts of continents still carry some small plant and animal remnants of their earlier biota (animal and plant life), and they also have been extensively modified by evolution, adaptation, and the arrival of new species. By contrast, the other islands, which emerged via geological processes such as volcanism, possessed no terrestrial life, but over long periods, winds, ocean currents, and the feet, feathers, and digestive tracts of birds brought the seeds of plants and a few species of animals. Only those species with ways of spreading to these islands were able to undertake the long journeys, and the various factors at play resulted in diverse combinations of new colonists on the islands. One estimate is that the distribution of plants was 75 percent by birds, 23 percent by floating, and 2 percent by wind.
    The migration of Oceanic biota was generally from west to east, with four major factors influencing their distribution and establishment. The first was the size and fertility of the islands on which they landed, with larger islands able to provide hospitality for a wider range of species. Second, the further east the islands, generally the less the species diversity, largely because of the distance that had to be crossed and because the eastern islands tended to be smaller, more scattered, and remote. This easterly decline in species diversity is well demonstrated by birds and coral fish. It is estimated that there were over 550 species of birds in New Guinea, 127 in the Solomon Islands, 54 in Fiji, and 17 in the Society Islands. From the west across the Pacific, the Bismarck Archipelago and the Solomon Islands have more than 90 families of shore fish (with many species within the families), Fyi has 50 families, and the Society Islands have 30.Third, the latitude of the islands also influenced the biotic mix, as those islands in relatively cooler latitudes, notably New Zealand, were unsuited to supporting some of the tropical plants with which Pacific islands are generally associated.
    Finally, a fourth major factor in species distribution, and indeed in the shaping of Pacific ecosystems, was wind. It takes little experience on Pacific islands to be aware that there are prevailing winds. To the north of the equator these are called north-easterlies, while to the south they are called south-easterlies. Further south, from about 30° south, the winds are generally from the west. As a result on nearly every island of significant size there is an ecological difference between its windward and leeward (away from the wind) sides. Apart from the wind action itself on plants and soils, wind has a major effect on rain distribution. The Big Island of Hawaii is often cited as a prime example; one can leave Kona on the leeward side in brilliant sunshine and drive across to the windward side where the city of Hilo is blanketed in mist and rain.  [br] The passage supports which of the following statements about species on volcanic islands?
选项 A、Volcanic island species are unlike the species found in other Pacific Ocean locations.
B、Volcanic islands lack the diversity of species found elsewhere in the Pacific.
C、Volcanic island species are all transplants from distant locations and exist in combinations not found elsewhere.
D、Volcanic island species differ from those on other islands in that animal species show greater diversity than plant species do.
答案 C
解析 题目问“关于火山岛上的物种说法正确的选项”。根据第1段第3、4句，火山岛上本没有任何生物 (possessed no terrestrial life)，而经过漫长岁月，风、洋流和鸟类带来了(thought)很多植物种子和外来物种，且在各种因素共同作用下使得岛上的物种类别与其他地区不同(diverse combinations of new colonists)，故C项的表达概述了原文的这段话，符合题意。A项“火山岛上的物种跟太平洋其他地区的物种不同”，根据文意，火山岛上的物种是由其他地区迁徙过来的，因此有可能会在太平洋其他地区找到相似物种。故排除A项，同时也可排除B项“火山岛上不存在太平洋其他地区所具有的生物多样性”。D项“火山岛上的物种跟其他地区物种的主要差异在于动物种类比植物种类更为丰富”，在原文没有提及，故排除。
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