- #36
SW VandeCarr
- 2,199
- 81
Andy Resnick said:Living systems can repair themselves, at least to some degree.
Living systems also seem to require constant turnover of components- cells, proteins, etc.
OK. That's seems to be a good start. Both repair and maintenance can be thought of in terms of a system's ability to remain in a stable operating state. Both metabolism and replication at smaller scales are involved. Metabolism provides the energy for this. So we can have a system that maintains itself internally and makes copies of some of its components, but may not be able to copy itself in its entirety. So these systems would not qualify as life if we require living systems to make copies of themselves and evolve. Nevertheless such systems would be interesting, especially if they were able to maintain themselves indefinitely within a range of environmental parameters.
Interestingly, hurricanes are simple systems which show limited abilities to repair themselves. They maintain themselves over a short "lifetime" of up to two weeks by extracting energy from the environment, and they exhibit very identifiable structure and behavioral patterns. No one would suggest these things are alive, but they part of a class of systems known as dissipative structures in which some scientists also include living systems.
Individual organisms die, but by making copies of themselves individual living systems are in a sense operating as components in a larger system. That larger system might be a community of similar organisms or an even larger system which we might call an ecology. At this point, it becomes a matter of taste whether you want to call these larger systems "dissipative" if they can last for millions or even billions of years.
My point is that what we might call a living system might be better thought of as a component of a larger sustaining ecology and may be itself a sustaining ecology for a complex of subsystems which could also be called living systems such as individual cells in metazoa.
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