open access

https://hdl.handle.net/2115/38426

Early Eukaryotization of Life : Environmental Driving Forces of Evolution

英語

Metazoans

2008

21st Century COE for Neo-Science of Natural History, Hokkaido University

Origin and Evolution of Natural Diversity : Proceedings of the International Symposium, The Origin and Evolution of Natural Diversity, held from 1-5 October 2007 in Sapporo, Japan

3-12

International Symposium, "The Origin and Evolution of Natural Diversity". 1–5 October 2007. Sapporo, Japan.

The bottom-up approach (from the origin of life and on) provides deeper causal-historical understanding of the environmental factors that drive the metabolic evolution and the biological complexity growth. The biogenesis in the electron-rich conditions of the Hadean Earth was, probably, inevitable due to the energy flow as a powerful factor of dynamic ordering of the molecular structures. Hydrogen as a primary fuel of life and the metal catalysts, in particular, tungsten, iron and nickel, played a crucial role in the initiation of life. However the physical-chemical parameters of biosphere departed form the initial ones. Subsequent biological evolution was driven in a great degree by competition for access to hydrogen from the primary sources such as the degassing of the Earth interior or radiolysis, and from the simple hydrogen compounds via splitting the molecules of CH4, NH3, H2S, and at last, H2O in the oxygenic photosynthesis. The archaic metabolic pathways in the cell were superimposed by the new metabolic modules that have been formed due to the interaction with new environmental factors. This process and compartmentalization of the ancient biochemistry in vesicles and organelles etc. were resulted in the growing complexity of the cell. Symbiogenesis based on syntrophy, mutual dependence on the waste products of each other, was a key factor of early eukaryotization of the cell and of the biodiversity growth. Multidisciplinary synthesis of data reveals the timing of the most important events in early biosphere such as the earliest activity of the methanogens, origins of oxygenic photosynthesis, eukaryotic cell, and multicellular animals. New types of physiology related to those evolutionary events strongly affected the global biogeochemical cycles, sedimentogenesis and climate.

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BA85842508