Non biological processes

Another important method for the detection of early life forms involves the ratio of the two carbon isotopes 12C and 13C. The lighter isotope 12C ( normal carbon ) is incorporated preferentially into biomolecules, so that the value of the ratio of 13C to 12C can indicate the presence of material which was formed in living things. It must of course be certain that other, non-biological processes can be excluded, though it is questionable whether this is always possible, in particular when we are unsure of the geological processes which occurred 3 1 billion years ago. 

Fig. 4.15. The biological carbon cycle. Thick arrows — biological processes, thin arrows — non-biological processes (modified from ref. [68])... 

The possibility that carbohydrate-ammonia reactions may participate in non-biological processes of humus formation under natural soil conditions received much attention during the period 1950-1960. Unlike the Mai Hard or "browning reaction, in which melanoidin pigments are formed in mixtures of sugars ana ammo acias in acidic media the ammonia reaction was... 

Bioremediation in situ is much more complicated than the system used in the laboratory controlled condition. Microorganisms in natural community interact with each other and also with other organisms and plants such interactions are more complicated than the scientific technique can delineate simply. Because of this, more systematic approaches are needed to reveal the connectivity between these biological factors and non-biological factors to understand the underlying processes. 

The usual emphasis on equilibrium thermodynamics is somewhat inappropriate in view of the fact that all chemical and biological processes are rate-dependent and far from equilibrium. The theory of non-equilibrium or irreversible processes is based on Onsager s reciprocity theorem. Formulation of the theory requires the introduction of concepts and parameters related to dynamically variable systems. In particular, parameters that describe a mechanism that drives the process and another parameter that follows the response of the systems. The driving parameter will be referred to as an affinity and the response as a flux. Such quantities may be defined on the premise that all action ceases once equilibrium is established. 

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