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1·Of the 7,000 alien species in the United States—out of a total of 150,000 species—only about 10% are invasive.

在美国总共15万的物种中，有7000种外来物种，当中只有10%是入侵物种。

2·Of the 7,000 alien species in the United States—out of a total of 150,000 species—only about 10 percent are invasive.

在美国总共15万的物种中，有7000种外来物种，当中只有10%是入侵物种。

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

生态学家通常把外来物种定义为人们偶然或故意带到新地方的物种。

4·A number of scientists question the assumption that the presence of alien species can never be acceptable in a natural ecosystem.

一些科学家质疑这样的假设，即在自然生态系统中，外来物种的出现是绝对不会被接受的。

5·Only a small percentage of alien species cause problems in their new habitats, said Don Smith, professor of ecology and evolutionary biology at the University of Tennessee.

田纳西大学生态学和进化生物学教授唐·史密斯说：“只有一小部分外来物种会在新栖息地引发问题。”

6·Only a small percentage of alien species cause problems in their new habitats,'' said Don Smith, professor of ecology and evolutionary biology at the University of Tennessee.

“只有一小部分外来物种会在它们的新栖息地引发问题。”田纳西大学生态学和进化生物学教授唐·史密斯说。

7·Imagine that an alien species landed on Earth and, through their mere presence, those aliens caused our art to vanish, our music to homogenize, and our technological know-how to disappear.

想象一下，外星物种登陆地球，而他们的存在会让我们的艺术消逝，同化我们的音乐，也让我们的技术知识消失了。

8·What can be done about invasive alien species?

怎样处理外来入侵的有害物种？

9·This bizarre alien species has the unsettling appearance of an animated skeleton.

这个奇异外星种族的外表活像一具骷髅，令人坐立难安。

10·Conservation organizations bill alien species as the foremost threat to native wildlife.

保育机构把外来物种列为原生物种的头号威胁。