by University of Chicago Press Journals, August 30, 2017 in ScienceDaily

To date, about 1.5 million species have been formally described in the scientific literature, most of them insects. Proportionally, bacteria comprise less than 1% of all described species.

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In a new paper published in The Quarterly Review of Biology (September 2017), researchers from the University of Arizona have estimated that there are roughly 2 billion living species on Earth, over a thousand times more than the current number of described species.