2018年6月六级听力真题(第2套)|录音1

历年英语六级考试听力真题附答案,专辑首页简介有全套六级资料，如果想获取更多英语资料，可以在评论区留言或者私信我哦！

Recording 1

Government‘s private groups and indivisuals spend billions of dollars a year trying to route out non-native organisms that are considered dangerous to ecosystems and to prevent the introduction of new intruders.

But a number of scientists question the assumption that the presence of alien species can nevr be acceptable in a natural ecosystem.

They say that portraying introduced species as inherently bad is an unscientific approach. “Distinctions between exotic and native species are artificial”，said Dr. Michael Rosenspeek， a professor of evolutionary biology at the University of Arizona.

“Because they depend on pegging a date and calling the plans on animals that show up after the date， exotic.”

Ecosystems free of species to find as exotic are by default consider the most natural.

“You can‘t roll back the clock and remove all the exotics or fix habitats，” Dr. Rosenspeek said， “Both native and exotic species can become invasive，and so they all have to be monitored and controlled when they begin to get out of the hand ”

At its core， the debate is about how to manage the world‘s remaining natural ecosystems and how and how much to restore other habitats.

Species that invade a territory can harm ecosystems，agriculture and human health.

They can threaten some native species or even destroy and replace others.

Next habitat loss，these evasive species represents the greatest threat to bio-diversity worldwide， many ecologists say.

Ecologists generally define an alien species as one that people accidentally or deliberately carried to its new location.

Across the American continents，exotic species are those introduced after the first European contact.

That date rounded of to 15 AD， represents what ecologist considered to have been a major shift in the spread of species including crops and life stock as they began to migrate with humans from continent to continent.

“Only a small percentage of alien species calls problems in their new habitats，”said Don Smith，professor of ecology and evolutionary biology at the Univiersity of Tenacy.

“Of the 7000 alien species in the United States，out of a total of 150 species，only about 10% are invasive，”he pointed out，“The other 90% have fit into their environments and are considered naturalized. ”

“Yet appearances can deceive，”ecologiest caution，“and many these exotics may be considered acceptable only because no one has documented their harmful affects .What is more， non native species can appear harmless then turn invasive.”

16.What assumption about introduced species is challenged by a number of scientists？

A) They will root out native species altogether.

B) They contribute to a region's biodiversity.

C) They pose a threat to the local ecosystem.

D) They will crossbreed with native species.

17.What does Dr. Michael Rosenspeek think of exotic native species ？

A) Their classifications are meaningful.

B) Their interactions are hard to define.

C) Their definitions are changeable.

D) Their distinctions are artificial.

18. What does Professor Don Smith say about alien species？

A) Only a few of them cause problems to native species.

B) They may turn out to benefit the local environment.

C) Few of them can survive in their new habitats.

D) Only 10 percent of them can be naturalized.

录音-1：政府的私人团体和非政府组织每年花费数十亿美元，试图清除被认为对生态系统有危险的非本地生物，并防止新的入侵者的引入。但是，许多科学家质疑一种假设，即自然生态系统中永远不能接受外来物种的存在。他们说，把外来物种描述成天生的坏物种是一种不科学的方法。亚利桑那大学进化生物学教授迈克尔·罗森斯佩克博士说:“外来物种和本土物种之间的区别是人为的。”“因为他们依赖于确定一个日期，并把约会后出现的动物称为异域动物。”没有外来物种的生态系统被默认为最自然的生态系统。“你不能让时间倒流，消灭所有外来物种或修复它们的栖息地，”罗森斯派克说，“本土和外来物种都可能成为入侵物种，因此，当它们开始失去控制时，必须对它们进行监测和控制。”这场辩论的核心是如何管理世界上现存的自然生态系统，以及如何以及在多大程度上恢复其他栖息地。入侵领土的物种会损害生态系统、农业和人类健康。它们可以威胁到一些本地物种，甚至破坏和取代其他物种。许多生态学家说，其次是栖息地的丧失，这些逃避的物种是对全球生物多样性的最大威胁。生态学家通常将外来物种定义为人们偶然或故意带到新地方的物种。在美洲大陆，外来物种是指在第一次与欧洲人接触后引入的物种。公元15年左右的这一天，代表了生态学家认为的包括农作物和生命资源在内的物种传播的一个重大转变，因为它们开始随着人类从一个大陆迁移到另一个大陆。Tenacy大学的生态学和进化生物学教授Don Smith说:“只有一小部分外来物种在它们的新栖息地遇到了问题。”“在美国的7000个外来物种中，总共有150个物种，只有大约10%是入侵物种，”他指出，“其他90%已经适应了它们的环境，被认为是归化了。然而，“生态学家警告说，”许多外来物种被认为是可以接受的，只是因为没有人记录过它们的有害影响。更重要的是，非本土物种可能看上去无害，然后变成了入侵物种。

16.哪些关于外来物种的假设受到了许多科学家的挑战?

17.迈克尔·罗森斯佩克博士对外来原生物种有什么看法?

18. 唐·史密斯教授对外星物种有什么看法?