How Much Life Is There on Earth?: Scientific American Podcast（一）
by David Biello
The charismatic[超凡魅力的] megafauna[巨型动物群] may get all the attention, but it's amoebas, nematodes and microbes that make up the bulk of life on Earth. So how many microbes are in the sea floor? A new analysis published in Proceedings of the National Academies of Science suggests there are fewer cells than previously proposed.
Based on transects[切面] and sediment[沉积] samples, scientists now estimate that there are 29, 000 quadrillion[千的六次方] cells in the subsurface of the ocean—their numbers constrained by a lack of available food in places where sedimentation rates are low. Of course, it is microbes living in just such extreme conditions that are challenging scientists' notion of what constitutes life by surviving for thousands of years.