V. Life's Corporeal Evolution Develops, Encodes and Organizes Itself: An EarthWinian Genesis Synthesis

4. Multicellular Fauna and Flora Organisms in Transition

Xing, Jianhua, et al. Computational Cell Biology. Interface Focus. 4/20140027, 2014. Virginia Tech and University of Cincinnati scientists introduce a special issue as another example of the on-going evolutionary revolution to better understand organismic life by virtue of equally real, independent, pervasive dynamic, modular, network and systems phenomena. A notable paper is It is Not the Parts, but How They Interact that Determines the Behavior of Circadian Rhythms across Scales and Organisms by Dan DeWoskin, et al.

As in physics and chemistry long ago, molecular life sciences are undergoing a foundational revision from empirical to mathematical. This trend has been prompted by insufficiency of the reductionist approach to provide quantitative explanations and predictions for the properties of molecular regulatory systems, whose observed behaviours are typically emergent phenomena governed by interactions between multiple components. A now classical example of this situation is the study of biological oscillations, such as circadian rhythms and the cell cycle, where the most significant properties of oscillation (period, amplitude, robustness, etc.) are non-trivially related in general to the details of the underlying network.

Yamagishi, Jumpei, et al. Symbiotic Cell Differentiation and Cooperative Growth in Multicellular Aggregates. PLoS Computational Biology. Online October, 2016. With Neri Salto and Kunihiko Kaneko, University of Tokyo biologists advance their studies of life’s persistent symbiosis of entity and assembly, which here is seen to foster nested stages of beneficial complexities and an emergent evolution. In this case, generic developmental systems theory explains how such groupings become wholly viable through reciprocal divisions of labor. See also Prof. Kaneko’s chapter in the 2016 volume Multicellularity (search Niklas).

Unicellular organisms, when aggregated under limited resources, often exhibit behaviors akin to multicellular organisms, possibly without advanced regulation mechanisms, as observed in biofilms and bacterial colonies. Cells in an aggregate have to differentiate into several types that are specialized for different tasks, so that the growth rate should be enhanced by the division of labor among these cell types. To consider how a cell aggregate can acquire these properties, most theoretical studies have thus far assumed the fitness of an aggregate of cells and the ability of cell differentiation a priori. In contrast, we developed a dynamical-systems model consisting of cells without assuming predefined fitness. The model consists of catalytic-reaction networks for cellular growth. By extensive simulations and theoretical analysis of the model, we showed that cells growing under the condition of nutrient limitation and strong cell-cell interactions can differentiate with distinct chemical compositions. They achieve cooperative division of labor by exchanging the produced chemicals to attain a higher growth rate. The conditions for spontaneous cell differentiation and collective growth of cells are presented. The uncovered symbiotic differentiation and collective growth are akin to economic theory on division of labor and comparative advantage. (Summary)

Zimmer, Carl. At the Water’s Edge: Macroevolution and the Transformation of Life. New York: The Free Press, 1998. The narrative story of the transition from fish to tetrapod and from land mammal to whales.

Zimmer, Carl. The Tangled Bank: An Introduction to Evolution. Greenwood Village, CO: Roberts and Co, 2009. A beautifully organized, illustrated and written text tour of the grandeur of Darwinian naturally living systems.

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