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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. 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. 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 used a chemical process called enzymatic catalysis to consume naturally occurring amino acids, sugars, and other organic compounds that had formed spontaneously in the atmosphere then dissolved in liquid water. Because of this chemical process, scientists sometimes call these beings chemo-heterotrophic anaerobes. Upon digestion of these molecules, early bacteria produced methane and carbon dioxide as waste products. Fermenting bacteria would be today's analog of these early creatures. To make beer, barley or wheat is combined with water to make a carbohydrate mash. Bacteria eat the sugars and produce alcohol and CO2 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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