Biology Reference
In-Depth Information
this kind is that some components are products of reactions catalyzed by other
components whose formation depends recursively on the action of the whole
network.
A NTSM organization constitutes a special case of the general principle of
self-maintenance. Whereas the common feature of all forms of SM is a more
or less robust but simple form of recursivity, what is specific in our case is
that the whole organization is a potentially self-modifying form of SM.
10
This
organization is potentially capable of generating open forms of recursivity, as
a change in the initial conditions can bring about new molecular structures,
which in turn may produce new forms of organization indefinitely. Such an
organization can explore an unlimited
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variety of new molecular combinations
and transformation processes leading to new, more complex forms of organiza-
tion in the context of reaction webs where a reaction can directly or indirectly
influence another, until a certain recursivity (closure) property is reached. The
system is self-maintaining because of the recursive and holistic form of its orga-
nization: the global dynamics is necessary for the maintenance of (many of)
the reactions of the system and these reactions are in turn necessary for the
maintenance of the whole system ('metabolic' closure
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). This is the basic idea
behind Rosen's (1971, 1973) 'M, R-systems' or Kampis's (1991) 'component
production systems'. A NTSM organization is in fact the core of a metabolic
organization.
Along with this capacity to generate internal variety, a sustainable process
of increase in complexity requires ways of preserving it. Only those novel
forms of complexity contributing to the maintenance of-or being functional in -
the organization that generated them can be preserved. Typically, the way to
retain complexity is by stabilizing it. There are several ways to create stability
within a dissipative organization: from the production of certain structurally
complex components that are thermodynamically stable and 'localize' degrees
of complexity to functional reorganization in hierarchical levels.
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To sum up,
a SM organization has the capacity to preserve the generated complexity if it
is able to recruit it for a further, more efficient (ultimately, more stable), form
of SM. In other words, by 'jumping' to another more efficient form of SM, a
system can preserve the generated complexity.
10
M. Bickhard (2000) uses the term 'recursive SM' with a very similar meaning.
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This limitless is only potential, because, as we shall see, as the complexity of the organization increases, its
brittleness also increases.
12
As has recently been pointed out by Letelier et al. (2006) a nontrivial idea of 'metabolic closure' is more
demanding than that of autocatalytic closure, such that in the former the circularity is a property of the global
connectivity in the entire network, not a property of a single reaction.
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Fast and reliable reproduction is also an indirect way to increase the stability of a given organization. We
shall further discuss the origin and consequences of this mechanism.
