Biochemical and geochemical aspects of early biological evolution



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Comparisons of the physiologies of modern bacteria have been used to speculate about the evolution of metabolic processes. Sequences of macromolecules from various groups of organisms have been determined and statistically compared to derive bacterial phylogenies. The results obtained from both these approaches are synthesized into a scheme outlining the evolution of major metabolic pathways. Although paleontological evidence is of limited value, geochemical analyses of Precambrian rocks have yielded clues about the nature of early life. This evidence, when considered with the biological scheme developed here, allows the construction of a working model of procaryotic evolution. This working model is applied to analyses of samples from the Gunflint Iron Formation in this report. Samples from a stromatolitic and planktonic facies are analyzed and compared. No significant differences are observed in the bitumens from the two facies. The distribution of n-alkanes and the indications of cyclic hydrocarbons (including steranes) suggest that the flora consisted primarily of procaryotes, some of which were able to respire aerobically. The presence of cyanobacteria is also indicated. The model developed in this report facilitated the estimation of evolutionary progression that had occurred prior to two billion years ago.



Microorganisms--Evolution, Biogeochemistry, Geomicrobiology