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. 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!
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