And I agree with both Onar and Mike that "self-producing"
is a necessary part of any definition of "being alive" (vs. being
dead). Self-re-production provides a way (through alterations to
some kind of stored "self-image") for variations among life-forms.
I like to think of the self-producing idea as follows (in
comparing it to something that isnt self-producing).
Something that isnt self-producing (example a machine) is
something in which the parts were manufactured before assembly.
The disjoint parts were then put together into some ensemble (or
network). This ensemble could then be hooked up to some external
power source (for example, electrical or chemical) and it does work
(dissipates). Some parts, though, after a while, will degrade, break,
or otherwise become nonfunctional, and have to be replaced. The
system can be turned off, taken apart, parts swapped, put back
together, and started back up. Also, even if it were possible for a
machine to be able to (from a large bin of parts) construct an exact
copy of itself, it wouldnt be self-producing.
Self-producing, as I understand it, means that every part of
a system is continually being turned over. The material that makes
up an identifiable part was manufactured (or processed) by the
system itself. For example, in a cell, lysosomes are continually
degrading complex molecules while ribosomes are manufacturing
new ones. There is a flow-through of material (that makes up the
parts) through the system. This is in addition to a flow-through of
energy.
Both a cell and an internal combustion engine takes in
carbon substrates and oxygen and give off carbon dioxide and
water. The gasoline oxidizes a carbon substrate and reduces
oxygen. The cell does the same thing. Through glycolysis, the
citric acid cycle, the electron transport chain and fatty acid
synthesis, carbon substrates are oxidized to CO2 and oxygen is
reduced to water.
Both systems are dissipatory and both can do work
(provide a local increase of free energy at the expense of the
environment). One important distinction, though, is that the parts
in the gasoline engine (the pistons, etc) are not continually being
produced in the process. In the cell, the biochemical molecules
responsible for the oxido-reduction reactions are continually being
turned over (replaced) from within. The parts in the gasoline
engine can only be replaced from outside of the system (by the
mechanic). The parts in the cell are replaced from within (by the
cell itself).
Can anybody think of a man-made self-producing system of this nature?
Jeff Prideaux