Proterozoic
The Proterozoic (pronunciation: /ˌproʊtərəˈzoʊɪk, prɔː-, -trə-/) is a geological eon representing the time just before the proliferation of complex life on Earth. The name Proterozoic comes from Greek and means "earlier life", the Greek root protero-,means "former, earlier" and zoic-, means "animal, living being". The Proterozoic Eon extended from 2500 Ma to 541 Ma (million years ago), and is the most recent part of the Precambrian Supereon. It is subdivided into three geologic eras (from oldest to youngest): the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic.
The well-identified events of this eon were the transition to an oxygenated atmosphere during the Paleoproterozoic; several glaciations, which produced the hypothesized Snowball Earth during the Cryogenian Period in the late Neoproterozoic Era; and the Ediacaran Period (635 to 541 Ma) which is characterized by the evolution of abundant soft-bodied multicellular organisms and provides us with the first obvious fossil evidence of life on earth.
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