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Krasnow Institute > Monday Seminars > Abstracts CANALIZATION, PHYSICS, GEOMETRY, AND EVOLUTION: A DISCUSSION Ann B. Butler, Research Professor, Krasnow Institute
Traditional NeoDarwinian evolutionary theory regards genes as abstract informational entities that allow a random exploration of phenotypes. In a recent workshop on organization at the Konrad Lorenz Institute the discussion focused on the idea that since phenotypes operate in the world of chemistry and physics, the only meaningful exploration of phenotypes are those so constrained by physical law. That is, genes can only reify (instantiate for the computer scientists) those changes which are meaningful in a restricted domain given the environment. Examples will be given from cellularity, biochemical networks, and morphogenesis. At the cellular level, one of the most basic needs of any single cell is to be able to sense its environment and to respond to environmental conditions in an adaptive way. Both a single-celled organism and a single cell within a multicellularorganism have mechanisms involving signalling molecules that affect the cell membrane, allowing the internal cell mielieu to sense the external environment, whether it be the pond, for example, in which it dwells or, in multicellular organisms,the presence of other cells around it. This situation constitutes the most simple and fundamental of all "nervous systems." Creating an ordered assembly of cells, or morphogenesis, is a fundamental process necessary to achieving a multicellular organism, and cell-to-cell communication is essential to this process. Morphogenesis is also an extremely complex process involving the interactions of developmental units called modules, which produce extensive order from disorder transformations. The developmental modules allow for variation to occur by the internal evolutionary processes of dissociation (temporal or spatial), duplication and divergence, and co-option, and selection then acts on the phenotypes produced. Cell-to-cell communication achieves a new level of importance in animals due to the ability of some cells to produce long processes. These processes are the axons of nerve cells, and their cell-to-cell signalling molecules are the neurotransmitters and neuromodulators. The extreme complexity of the vertebrate head and brain is in fact a derivative of relatively simple events that affected genetic and developmental modules and the resultant order from disorder processes based on modular interactions and hierarchical organization.
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