For 2 billion years, all organisms on Earth are unicellular, and they likely lived in the oceans, shielded from the hard ultraviolet light of the sun but then something remarkable happened, Photosynthesis.

20以来，地球上的所有生物都是单细胞的，它们很可能生活在海洋中，不受太阳紫外线的照射，但随后发生了一件非同寻常的事情，就是光合作用的产生。

Why don't we get unicellular elephants, or blue whales, or brown bears?

为什么我们没有单细胞的象、蓝鲸或棕熊呢？

We have isolated around 30 or 40 strains already of unicellular eukaryotes.

马拉 vin：我们已经分离出了约30到40株单细胞真核生物。

Most unicellular reproduction is asexual, meaning one organism, on its own, can reproduce itself.

多数单细胞生物的繁殖是无性的，这意味着一个生物体可以独自行自我繁殖。

We have evidence of the first unicellular predators emerging around that time.

我们有证据表明，最早的单细胞捕食者约是在那个时期出现的。

These organelles, the descendants of bacteria that cosied up with the ancestors of human beings back when those ancestors were unicellular, retain from their days of independence a list of other jobs.

这些细胞器是细菌的后代， 它们在人类的祖先还是单细胞生物时就与这些祖先建立了亲密关系。即便在独立时期， 它们也保留了一系列其他职责。

In the 1940s, author Jack Williamson coined the term, " terraforming." To terraform is to create an ecosystem that supports living organisms—from large, complicated vertebrates, to simple, unicellular bacteria.

在 1940 代，作家杰克·威廉姆森 (Jack Williamson) 创造了“地形改造”一词。地形改造就是创造一个支持生物体的生态系统——、复杂的脊椎动物到简单的单细胞细菌。

The report ignores bacteria fungi and unicellular creatures like amoeba Using figures from the international union for conservation of nature or IUCN which publishes an annual red list of threatened species.

该报告忽略了细菌、真菌以及变形虫之类的单细胞生物，使用了国际自然保护联盟（IUCN）发布的度受威胁物种红色名录中的数据。

And actually everything on here from animals all the way over to fungi, down in here to unicellular organisms and plants and all these things are eukaryotes.

实际上，动物到真菌，再到这里的单细胞生物和植物，所有这些生物都是真核生物。

Which led to the formation of unicellular life, likely near a hydrothermal vent beneath the surface of the ocean.

这导致了单细胞生命的形成，很可能是在海洋表面下的热液喷口附近。

A further argument against the simple wear and tear theory is the observation that the time within which organisms age lies between a few days (even a few hours for unicellular organisms) and several thousand years, as with mammoth trees.

反对简单磨损理论的另一个论点是观察到生物体老化的时间介于几天（对于单细胞生物甚至是几个小时）到几千之间，就像猛犸象树一样。

Again this relationship is valid not only for birds, but also, similarly on average within the systematic unit, for all other organisms (plants, animals, unicellular organisms).

同样，这种关系不仅适用于鸟类，而且在系统单位内，平均而言，也适用于所有其他生物（植物、动物、单细胞生物）。

But these could be the fossils of colonial unicellular organisms, bacterial mats, or something else entirely.

但这可能是群居单细胞生物、细菌垫或其他完全不同的东西的化石。

If that's true, though, then there's a problem: Most unicellular life at the time was photosynthetic -- like cyanobacteria and phytoplankton – and they need light to live.

如果这是真的，那么就有一个问题：当时多数单细胞生命都是行光合作用的， 比如蓝藻和浮游植物， 它们需要光照才能生存。

Those are simple unicellular life forms that thrive without oxygen and get energy by scavenging what molecules they find.

这些是简单的单细胞生物，它们在没有氧气的情况下繁盛生长，通过摄取所找到的分子来获取能量。

Yet even the biggest unicellular organisms have limits, and none grows nearly as large as the elephant, whale, or bear.

然而，即便是最的单细胞生物也存在生长极限，没有任何一种能长得像象、鲸鱼或熊那样庞。