Crust as a Platform for Prokaryotic Life
much of the history of living things, organisms were exclusively primitive,
single-celled forms such as bacteria and cyanobacteria.
Then as now, these simple prokaryotic cells lacked
a nucleus and were relatively small, but they already contained the
same basic hereditary materials found in all life today—DNA
and RNA. Many of these early life forms relied on chemosynthesis
for their energy, deriving it from the chemicals around them instead
of from sunlight or other organisms. Some inhabited environments that
seem hostile, such as deep-sea hydrothermal vents.