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Exploratour - Life on Earth

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Corel Photography

As a group, the first life forms on Earth were heterotrophic, meaning that they ate food which came from somewhere else. Because there was virtually no oxygen in the atmosphere at this time, these bacteria did not breathe oxygen. The fossils of some these oldest known forms of life, called Archaea, have been found in Australian rocks dating back 3.5 billion years.

For food, Archaea probably consumed naturally occuring amino acids. Amino acids, sugars, and other organic compounds formed spontaneously in the atmosphere then dissolved in liquid water. Upon digesting these molecules, early bacteria produced methane and carbon dioxide as waste products. Fermenting bacteria would be an example from today of what these early creatures might have been like. To make beer you put barley or wheat with water. The broken down barley and wheat turns into sugar. Fermenting bacteria eat the sugars and produce alcohol and carbon dioxide gas as waste products. Beer manufacturers then remove the bacteria and carbon dioxide, and put the alcohol in bottles. In the early Earth, the alcohol and carbon dioxide became part of the natural environment.

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Last modified June 4, 2010 by Randy Russell.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF