limits for simple life are governed primarily by the chemistry
concerned, and whether or not it can take place under given conditions.
As we see, simple microbial life can survive in the cold, or heat,
vacuum, and harsh radiation of space (go to extremophiles).
It can cope with caustic and acidic chemicals, and arid conditions
too. Many biologists have now concluded that all life needs
in order to cling on to some sort of existence is chemical "drivers"
for metabolism - and these can be as simple as a supply of hydrogen
- and liquid water. If
this is so, then the range of life
habitats in the Universe may be much more diverse and numerous
than we had assumed just a few years ago.
while simple life may be able to adapt to survive in such extreme
environments, such conditions impose severe limitations on the
evolution of such lifeforms into more complex beings. Living
organisms exploit their environment. They change or develop
to take advantage of it, through the process we call evolution.
Environments put various limits on such development - temperature
and chemistry being examples. These limitations can pose
severe problems for organisms to overcome. Sometimes this
takes a long time - millions or even billions of years.
Other times the limitations could be so severe that organisms
may never overcome the problem.
the less, it should not be assumed that there is any "force of
nature" driving simple living organisms towards higher complexity
and the development of what we refer to as advanced life forms.
There is no evidence in nature for this assumption. Complexity
seems to occur because it can rather than because it needs to.
to think about: How does this
fit in with Darwinian Evolution?