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  3. Plant and Animal Life of the Pacific IslandsP1: The Pacific Islands region cove

Plant and Animal Life of the Pacific IslandsP1: The Pacific Islands region cove

游客2024-01-03  23
问题 Plant and Animal Life of the Pacific Islands
P1: The Pacific Islands region covers 32 million square kilometers and is one of the richest, most complex terrestrial and marine ecosystems on Earth. Some islands that used to be parts of continents still carry some small plant and animal remnants of their earlier biota, providing clear examples of evolution and interesting patterns of colonization, adaptation, and speciation. Cn the contrary, some other islands arose due to volcanic activity or reef growth, which usually subside over time due to erosion and changing sea levels. When islands emerge, they undergo the process of ecological succession as species colonize the island. 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 due to being transported by birds, 23 percent by floating, and 2 percent by wind.
P2: Four major factors account for the fact that the plants and animals on Oceanic islands largely migrate from west to east. The size and fertility of the territory of certain islands is the first determining factor. That is, the larger the islands are, the wider the range of species they are able to support. Second, the further east the islands are, generally the less the diversity of species found there, largely because the eastern islands tended to be smaller, more scattered, and remote, as evidenced by the easterly decline in species diversity of 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 , Fiji 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.
P3: The fourth factor that has influenced species distribution and the shaping of Pacific ecosystems was wind. There are strong prevailing winds throughout the Pacific Ocean, which has been known for centuries due to scientific development. Those in the northern hemisphere are called "North-easterlies", while their counterparts of the southern hemisphere are known as "south-easterlies." Further south, beginning from approximately thirty degrees south, the winds are mostly from the west. Therefore, on nearly every single island of large scale exists an ecological difference between its windward and leeward sides. Apart from the wind action itself on plants and soils, wind has a major effect on rain distribution. The Big Island of Hawaii offers 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.
P4: The long geological isolation of the Pacific islands and their particular climatic conditions have combined to create a unique and spectacular ecosystem. New species cannot immigrate via land, and instead must arrive via air, water, or wind. As a result, organisms with high dispersal capabilities, such as plants and birds, are much more common on islands than are poorly dispersing taxa like mammals. Since immigration of predators and competitors is limited, many species of flightless and ground-nesting birds are able to persist in these new niches. This results in a high occurrence of endemism, where species are unique to a localized area. Besides, endemism is often the result of adaptive radiation, when a single species colonizes an area and rapidly diversifies to fill all of the available niches. These endemic species derived form adaptive radiation are often small in number, unused to serious predation, limited in range, and therefore vulnerable to disruption.
P1: The Pacific Islands region covers 32 million square kilometers and is one of the richest, most complex terrestrial and marine ecosystems on Earth. ■ Some islands that used to be parts of continents still carry some small plant and animal remnants of their earlier biota, providing clear examples of evolution and interesting patterns of colonization, adaptation, and speciation. ■ On the contrary, some other islands arose due to volcanic activity or reef growth, which usually subside over time due to erosion and changing sea levels. ■ When islands emerge, they undergo the process of ecological succession as species colonize the island. ■ 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 due to being transported by birds, 23 percent by floating, and 2 percent by wind. [br] An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Drag your choices to the spaces where they belong. To review the passage, click on View Text.
Biodiversity on Oceanic islands is dependent on a number of factors.
Answer Choices
A Unlike Oceanic islands that were once part of continental landmasses, islands formed by such geological processes as volcanism contain only plants and animals that could be transported there.
B An island’s size is less important than its latitude in determining species diversity.
C Though biodiversity is low on many Oceanic islands, many native species have evolved that are uniquely adapted to their local environments.
D Species distribution in Oceania is determined by the location of islands, their size, and the direction of the wind.
E Most Oceanic islands are similar to one another in latitude and contain plants and animals typical of tropical islands.
F The absence of natural predators on the eastern Oceanic islands allowed many species of large mammals to evolve that were capable of inhabiting a wide range of territory.
选项
答案 A，C，D
解析 【文章总结题】本文主要讲述影响大洋洲岛屿物种多样性的因素。大洋洲岛屿主要有两类，一种岛屿曾经是大陆的一部分，另一种是由地质运动产生的岛屿，这种岛屿上的生物大多是从别处迁徙而来；岛屿上土地规模以及肥沃程度会影响物种多样性，并且物种多样性从西到东递减，纬度和盛行风也会有一定的影响；一些岛屿的生物多样性不够多，但是因为没有捕猎者和竞争者，所以会有一些特有生物出现。所以涉及影响岛屿物种多样性的A、C、D选项正确，F属于细节偏离主旨，B、E与文章内容不一致。
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