A scenario for biological organization is proposed, based on numerical studies of the developmental process of interacting units with internal dynamics and reproduction. Diversification, formation of discrete and recursive types, and rules for differentiation are found as a natural consequence of such a system. The rule is formed through the internal representation of the surrounding units, and depends both on internal state and on interaction. The macroscopic robustness of the developmental process is shown to be a natural consequence of such a system. By introducing spatially localized mechano-chemical interactions, the emergence of a multi-cellular organism with a life history is demonstrated. Finally the consequence of our intra-inter dynamics to evolution is discussed, which leads to the genetic fixation of interaction-induced phenotypic diversification.
Basic problems in complex systems are surveyed in connection with Life. As a key issue for complex systems, complementarity between syntax/rule/parts and semantics/behavior/whole is stressed. To address the issue, a constructive approach for a biological system is proposed. As a construction in a computer, intra-inter dynamics is presented for cell biology, where the following five general features are drawn from our model experiments; intrinsic diversification, recursive type formation, rule generation, formation of internal representation, and macroscopic robustness. Significance of the constructed logic to the biology of existing organisms is also discussed.
Basic problems for the construction of a scenario for the Life are discussed. To study the problems in terms of dynamical systems theory, a scheme of intra-inter dynamics is presented. It consists of internal dynamics of a unit, interaction among the units, and the dynamics to change the dynamics itself, for example by replication (and death) of units according to their internal states. Applying the dynamics to cell differentiation, isologous diversification theory is proposed. According to it, orbital instability leads to diversified cell behaviors first. At the next stage, several cell types are formed, first triggered by clustering of oscillations, and then as attracting states of internal dynamics stabilized by the cell-to-cell interaction. At the third stage, the differentiation is determined as a recursive state by cell division. At the last stage, hierarchical differentiation proceeds, with the emergence of stochastic rule for the differentiation to sub-groups, where regulation of the probability for the differentiation provides the diversity and stability of cell society. Relevance of the theory to cell biology is discussed.
Studies on coupled map lattice, originally introduced for the study of spatiotemporal chaos, are surveyed, with the emphasis on the suppression of chaos, spatiotemporal intermittency, supertransients, and stability of fully-developed spatiotemporal chaos. Extensions of coupled maps to the global coupling and hyper-cubic lattices are also discussed. In these studies we note the emergence of the dynamics of a higher-level, as is called chaotic itinerancy. The chaotic itinerancy supports the succession of several quasi-stable states. Based on these studieds, the notion ``homeochaos" is presented as a mechanism on the dynamic stability supporting diversity. Last, some speculations on the diversity and collective stability are given in connection with the evolutionary process.
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