They are the reason for the many different kinds of life on Earth.

VOA: special.2009.12.01

There's a short story by the science fiction writer Orson Scott Card, where the basic point of the story is that of all the life forms in the universe, we, here on Earth, are the only ones that are mortal.

科幻作家Orson，Scott，Card写了一个短故事，该故事的主旨是,在宇宙的所有生命形式中，我们，在地球上是唯一终有一死的生命。

耶鲁公开课 - 死亡课程节选

He developed the theory of evolution that life on Earth developed through the process of natural selection.

VOA: special.2009.12.16