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An electron micrograph of Bacteria
Image courtesy of JPL/NASA

The First Living Cells

The first beings were probably much like coacervates. As a group, these bacteria are called heterotrophic anaerobes (ann-air-robes). Because there was virtually no oxygen in the atmosphere at this time, these bacteria were necessarily anaerobic, meaning they did not breathe oxygen. Heterotrophs, meaning "other feeders", are simply organisms that cannot make their own food. So "heterotrophic anaerobes" means they were creatures which ate some naturally occurring food and did not breathe oxygen. The fossils of some these oldest known forms of life have been found in Australian rocks dating back 3.5 billion years.

To create energy, these early bacteria probably consumed naturally occurring 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 combine barley or wheat and water. The broken down barley and wheat turns into sugar. Bacteria eat the sugars and produce alcohol and carbon dioxide gas as waste products. In the early Earth, the alcohol and carbon dioxide became part of the natural environment.

Over time, new life forms evolved which were able to get their energy from a different source -- the Sun!

Last modified June 4, 2010 by Randy Russell.

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Traveling Nitrogen is a fun group game appropriate for the classroom. Players follow nitrogen atoms through living and nonliving parts of the nitrogen cycle. For grades 5-9.

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