Biology Reference
In-Depth Information
emergent behavior.
7
Chemistry allows accumulative construction, a process of
interactive feedback between the organization of components and the accumula-
tive assembly of increasingly complex components, which is a consequence of
the combinatory - chemical - nature of molecules. This way, chemical networks
can reach a special plasticity or potential for diversification. This does not mean
that chemistry is enough for this process of increase in complexity. As we see in
biological systems self-assembly is also an important factor of the construction
of their complex organization, and once a high level of molecular complexity is
reached, there are even constructive processes of mechanical nature. But what I
want to stress here is that all these processes are possible due to the establishment
of a NTSM chemical organization.
8
Now, what does SM mean in this context? The basic idea is that of auto-
catalysis: molecule A could catalyze the formation of B, B of C, and C of A
(but of course many more reactions and side reactions can occur). Given a set
of specific initial conditions, a process of production of components may be
triggered, creating new components and catalysts, which in turn will produce
new ones, and so on, until the initial set of components is produced and the
whole process becomes recursively regenerated.
9
The key feature of a SM orga-
nization capable of increasing its complexity is that the circular loop involves
the generation of many (some of them stable) components that may act as local
and selective constraints (molecules and supramolecular structures). In other
words, an increasing part of the dynamical order is recorded in complex stable
structures/components (which in turn will allow more complex forms of orga-
nization). However, the maintenance of the system depends on the whole set
of relations, and is therefore a distributed, holistic phenomenon. The interesting
point here is that, once a certain threshold of complexity is crossed, the main-
tenance of an autocatalytic organization lies in the entire network, instead of in
single reactions (see footnote 12). Thus, the main characteristic of a system of
7
It is necessary but not sufficient. In fact, a chemical DS like a BZ system is a type of organization in which
the emergent pattern depends on dynamical factors, such as (the behavior of) concentrations or diffusion of
the components of the system, but not on changes of the relations of production (catalytic reaction rates)
among components. Thus, the emergent pattern is (like in purely physical DSs) nothing more than a global
correlation of billions of molecules allowing a different (according to some authors, more efficient) way to
dissipate energy but not a selective re-organization of the component-production relations that may change
the identity of the system. For example, a burning candle is a self-maintaining chemical system, in which the
macroscopic pattern-the flame itself-contributes to maintaining the organization of the system (by vaporizing
wax). However, the flame as a macroscopic, global constraint only plays this action, and therefore it is a trivial
form of SM.
8
This process, however, would be similar to what Evelyn Fox Keller (this issue) refers to as 'the iterative
processes of self-organization that occur in heterogeneous systems over time', because she considers the
formation of composite systems rather than composite structures (components).
9
Autocatalysis constitutes a simple example of the entangled relation between construction and organization
maintenance. A dissipative process is maintained through the construction of certain aggregates (catalysts)
that in turn modify the interactions in such a way that the organization will again produce such components.
