Sang Hoon Lee, Sebastian Bernhardsson, Petter Holme, Beom Jun Kim, Petter Minnhagen
To what extent do the characteristic features of a chemical reaction network
reflect its purpose and function? In general, one argues that correlations
between specific features and specific functions are the key to understanding a
complex structure. Yet specific features may sometimes be neutral and
uncorrelated with any system-specific purpose, function, or causal chain. Such
neutral features are caused by chance and randomness. Here we compare two
classes of chemical networks: one that has been subject to biological evolution
(the chemical reaction network of the metabolism in living cells) and one that
has not (the atmospheric planetary chemical reaction networks). Their degree
distributions are shown to share the very same neutral system-independent
features. The shape of the broad distributions is to large extent controlled by
a single parameter, the network size. From this perspective, there is little
difference between atmospheric and metabolic networks; they are just different
sizes of the same random assembling network. In other words, the shape of the
degree distribution is a neutral characteristic feature and has no functional
or evolutionary implications in itself; it is not a matter of life and death.
View original:
http://arxiv.org/abs/1112.3803
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