|Life Before Oxygen|
About three billion years ago, single-celled underwater bacteria similar to modern cyanobacteria consumed carbon dioxide as they photosynthesized, releasing oxygen in the process. In this way, an atmosphere full of volcanic carbon dioxide gradually changed into an oxygen-rich atmosphere in which animal life could survive, except for some primitive organisms, who retreated to oxygen-poor environments. This video segment shows researchers as they search for these organisms, which are now considered tiny time capsules from the time before there was oxygen on Earth. The segment is one minute thirty-nine seconds in length. A background essay and list of discussion questions are also provided.
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Source: Interactive NOVA "Earth". Copyright 2002-2006, WGBH Educational Foundation. All rights reserved.
DLESE Catalog ID: DLESE-000-000-009-851
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Publisher: WGBH Educational Foundation