大部分人不会意识到微生物的存在，因为他们的肉眼看不见，但事实上，微生物占据了地球大约一半的生物量，而所有的动物加起来，也不过占地球总生物量的千分之一。

Most people don't realize it, because they're invisible, but microbes make up about a half of the Earth's biomass, whereas all animals only make up about about one one-thousandth of all the biomass.

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