出国留学首选一诺留学

　　阅读部分

　　词汇题

　　diminish = decrease

　　rudimentary=primitive

　　readily=quickly

　　hasten = hurry

　　hence=thus

　　prolong=extend

　　divert=redirect

　　widespread = common

　　excessive e=too much

　　controversy=debate

　　strictly aquatic habitat = only live in aquatic environment

　　第一篇

　　题材划分：环境类

　　大部分淡水存在冰川中，可用的地表水只有40%左右。由于人们过度用来灌溉和饲养牲畜，所以地表水愈来愈少。当refill跟不上用的速度了，地表水就开始缺乏。地表水层由沙子石头等组成，水少了以后就开始collapse，出现一些holes，这样地表水层的空间就更小了。有个400米深的水井，人们就大量使用导致周围的浅一点地方都没有水了，人们只能废弃那些地方。后来又讲了一种叫做土地盐碱化的相关灾害对海边的影响。

　　相关背景资料：

　　Soilsalinity is the salt content in thesoil; the process of increasing the salt content is known as salinization. Saltsoccur naturally within soils and water. Salination can be caused by naturalprocesses such as mineral weathering or by the gradual withdrawal of an ocean.It can also come about though artificial processes such as irrigation.

　　Causes of soil salinity

　　The excess accumulation of salts, typicallymost pronounced at the soil surface, can result in salt-affected soils. Saltsmay rise to the soil surface by capillary transport from a salt-laden watertable and then accumulate due to evaporation. They can also become concentratedin soils due to human activity, for example the use of potassium as fertilizer,which can form sylvite, a naturally occurring salt. As soil salinity increases,salt effects can result in degradation of soils and vegetation.

　　Salinization as a processcan result from:

　　-high levels of salt inwater.

　　-landscape features thatallow salts to become mobile (movement of water table).

　　-climatic trends that favoraccumulation.

　　-human activities such asland clearing.

　　-Irrigation - salt runofffrom streets (in winter if the streets are salted for snow)

　　第二篇

　　题材划分：地质类

　　主要内容：火星是否存在生命体

　　火星探索发现表面没有水，减少了有生命的可能。很久以前，一颗火星的陨石飞到了地球的极圈，因为很冷所以能基本无污染的保存下来。科学家打开来检查，发现有种长得像地球远古生物(虫?)的生物，但是其他科学家说这个结构太小了，不可能有生物的基本功能。还发现了carbon的元素，这是地球生命产生的必须物质，但又有指出说这是地球生物的必须，还是不能证明火星能有生命。

　　相关背景资料：

　　The current understanding ofplanetary habitability—the ability of a world to develop environmentalconditions favorable to the emergence of life—favors planets that have liquidwater on their surface. Most often this requires the orbit of a planet to liewithin the habitable zone, which for the Sun extends from just beyond Venus toabout the semi-major axis of Mars. During perihelion, Mars dips inside this region,but the planet's thin (low-pressure) atmosphere prevents liquid water fromexisting over large regions for extended periods. The past flow of liquid waterdemonstrates the planet's potential for habitability. Some recent evidence hassuggested that any water on the Martian surface may have been too salty andacidic to support regular terrestrial life.

　　The lack of a magnetosphereand the extremely thin atmosphere of Mars are a challenge: the planet haslittle heat transfer across its surface, poor insulation against bombardment ofthe solar wind and insufficient atmospheric pressure to retain water in aliquid form (water instead sublimes to a gaseous state). Mars is also nearly,or perhaps totally, geologically dead; the end of volcanic activity hasapparently stopped the recycling of chemicals and minerals between the surface andinterior of the planet.

　　Evidence suggests that theplanet was once significantly more habitable than it is today, but whetherliving organisms ever existed there remains unknown. The Viking probes of themid-1970s carried experiments designed to detect microorganisms in Martian soilat their respective landing sites and had positive results, including atemporary increase of CO2 production on exposure to water and nutrients. Thissign of life was later disputed by some scientists, resulting in a continuingdebate, with NASA scientist Gilbert Levin asserting that Viking may have foundlife. A re-analysis of the Viking data, in light of modern knowledge ofextremophile forms of life, has suggested that the Viking tests were notsophisticated enough to detect these forms of life. The tests could even havekilled a (hypothetical) life form. Tests conducted by the Phoenix Mars landerhave shown that the soil has a alkaline pH and it contains magnesium, sodium,potassium and chloride. The soil nutrients may be able to support life, butlife would still have to be shielded from the intense ultraviolet light.

　　第三篇

　　题材划分：生物类

　　主要内容：两栖类动物在沙漠的生存

　　讲的是一种两栖动物，一个toad—个虾，如何在沙漠缺水的环境里生存的。主要是讲他们利用很短的湿润的季节进行繁殖来维持种族的繁衍;在旱季的时候，通过各种保护行为来生存下来。toad是长期在地下，然后在合适的时候出来产卵繁衍。还说了未成年的应对，比如水快没了的一些应对。toad存活率很低，因为缺水的话toad就会长得很小，然后toad内部有弱肉强食，外部又有其他捕食者。还讲了有水的时候才能活的一种虾，这种虾也是在盆地底层一直冬眠很久，直到合适环境迅速孵化，一般是冬天，因为冬天水会比较多，在十天左右的时间，然后迅速繁衍。

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