An electron micrograph of Bacteria
Image courtesy of JPL/NASA
The First Living Cells
The first beings were probably much like coacervates
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.
, 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!
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