Because complex species interactions may be involved, identifying a keystone species by removing the species and observing changes in the ecosystem is problematic.

由于其中可能涉及复杂的物种相互作用，通过移除一个关键物种并观察生态系统的变化来确定该物种是有问题的。

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Species interdependence in nature confers many benefits on the species involved, but it can also become a point of weakness when one species involved in the relationship is affected by a catastrophe.

在自然界中，物种的相互依赖给相关物种带来了许多好处，但当其中一个物种受到灾难的影响时，这种依赖也可能成为一个弱点。

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The China–US team say that invasive animal species increased from 1990 to 2003 by more than 30 per cent to 76 species, and invasive plant species tripled between 1995 and 2003.

来自中国和美国的研究小组指出，中国外来动物入侵物种的数量从1990年到2003年增加了30%，达到76种，而植物入侵物种在1995年至2003年翻了三倍。

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But the idea that species have evolved from simpler forms is less accepted by the public.

VOA: special.2009.12.01

Millions of humans affected by Alzheimer's disease, other species don't get Alzheimer's disease.

上百万人受阿尔茨海默氏症的侵扰,其它物种并不会得这种病

耶鲁公开课 - 生物医学工程探索课程节选

Vertebrate species,for example, decreased by nearly one-third between nineteen seventy and two thousand six.

VOA: special.2010.05.25

The other is that upgrading subspecies into species simultaneously increases the number of rare species (by fragmenting populations) and augments the biodiversity of a piece of habitat and thus its claim for protection.

ECONOMIST: Species inflation

No one knows the number of parasite species, but they appear to outnumber the nonparasite species by 4-to-1.

FORBES: Those Resourceful Bugs

Otherwise we are drawing a moral circle around our own species, even when the members of our own species protected by that moral boundary are not superior in any moral relevant characteristics to many nonhuman animals who fall outside the moral circle.

BBC: EATING