He reasoned that some single-celled creatures are known to enter a hibernation-like state and survive for years with no air or food.
他推断，已知的一些单细胞生物进入类似冬眠的状态，在没有空气和食物的情况下存活数年。
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The fossils buried in Pleistocene and earlier ocean sediments were of foraminifera—small, single-celled marine organisms that secrete shells of calcium carbonate, or calcite.
The ancestors of plants were photosynthetic single-celled organisms that gave rise to plants presumably lacked true roots, stems, leaves, and complex reproductive structures such as flowers.