A second important and related directionality emerges out of autocatalysis - that of centripetality. To see this one notes in particular that any change in B is likely to involve a change in the amounts of material and energy that are required to sustain process B. As a corollary to selection pressure one immediately recognizes the tendency to reward and support any changes that serve to bring ever more resources into B. Because this condition pertains to any and all members of the causal circuit, any autocatalytic cycle becomes the epicenter of a centripetal flow of resources toward which as many resources as possible will converge (Figure 3). That is, an autocatalytic loop defines itself as the focus of centripetal flows. A didactic example of such centripetality is coral reef communities, which by their considerable synergistic activities draw a richness of nutrients out of a desertlike and relatively inactive surrounding sea.
The centripetality generated by autocatalysis is a much-neglected and essential attribute of the life process. For example, evolutionary narratives are replete with explicit or implicit references to such actions as striving or struggling, but the origin of such directional behaviors almost always remains unmentioned. Such actions are simply postulated. Centripetality, however, appears to be at the very roots of such behaviors. To see this, one only needs to recognize that it is centripetality that gives rise to the much vaunted competition, which is the crux of evolutionary theory. For centripetality guarantees that, whenever two or more autocatalytic loops exist in the same system and draw from the same pool of finite resources, competition among the foci necessarily ensues. In particular, whenever two loops share pathway segments in common, the result of this competition is likely to be the exclusion or radical diminution of one of the nonoverlapping sections. For example, should a new element D happen to appear and to connect with A and C in parallel to their connections with B (Figure 4), then
if D is more sensitive to A and/or a better catalyst of C, the ensuing dynamics should favor D over B to the extent that B will either fade into the background or disappear altogether. That is, the selection pressure and centripetality generated by complex autocatalysis (a macroscopic ensemble) is capable of shaping and replacing its own elements. Perhaps the instances that spring most quickly to mind here involve the evolution of obli-gately mutualistic pollinators, such as yuccas and yucca moths, which coevolve with the yucca so as to displace other pollinators.
One notes in passing that the same tendency to replace B with D could as readily replace a defective or destroyed B with another similar component B', that is, autocatalysis lies behind the ability of living systems to repair themselves.
It becomes obvious that the autocatalytic system is no longer acting merely at the behest of externalities, but it is actively drawing ever more resources unto itself.In fact, the tendency of centripetality to transform as much as possible into itself lies at the very crux of evolutionary drive; for absent such striving, there would be no competition at the next level up.
Furthermore, one perceives autocatalytic action as the agency behind one of a pair of agonistic tendencies that together account for the patterns of life-forms and functions. On the one hand is the stochastic, entropic tendency to fall apart, which at the same time generates new diversities of form and behavior. Arrayed against the inevitable centrifugal drift toward disorder is the autocatalytic selection and centripetal pull toward greater activity and tighter organization. Opposing thrusts though they are, the continued development of life would be impossible without the actions of both.
Finally, the focal position that autocatalytic configurations of processes occupy in the phenomenon of life is aptly illustrated by considering what differs between a living organism (say a deer) and the same entity immediately upon death. The mass of the deer remains the same, as does its overall form, chemical constitution, embodied energy, and genomic configuration. What the live deer had that the dead deer no longer possesses is simply its configuration of autocatalytic processes.
See also: Ecological Network Analysis, Ascendency; Ecological Network Analysis, Energy Analysis.
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