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 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
have been found in Australian rocks dating back 3.5 billion years.
For food, 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.
Over time, new life forms evolved which were
able to get their energy from a different source -- the Sun!
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