Abstract
It is generally accepted that life requires structural complexity. However, a chaotic mixture of organic compounds like the one formed by extensive reaction sequences over time may be extremely complex, but could just represent a static asphalt-like dead end situation. Likewise, it is accepted that life requires a certain degree of structural order. However, even extremely ordered structures like mineral crystals show no tendency to be alive. So neither complexity nor order alone can characterize a living organism. In order to come close to life, and in order for life to develop to higher organisms, both conditions have to be fulfilled and advanced simultaneously. Only a combination of the two requirements, complexity and structural order, can mark the difference between living and dead matter. It is essential for the development of prebiotic chemistry into life and characterizes the course and the result of Darwinian evolution. For this reason, it is worthwhile to define complexity and order as an essential pair of characteristics of life and to use them as fundamental parameters to evaluate early steps in prebiotic development. A combination of high order and high complexity also represents a universal type of biosignature which could be used to identify unknown forms of life or remnants thereof.
Highlights
It is generally accepted that life requires structural complexity
The entropy (S) is given in units of J/K and may be defined thermodynamically as well as statistically. It unambiguously describes the state of a system regarding its disorder, even though it may be difficult to be determined in practice and even though the outcome may occasionally deviate from the human interpretation of disorder
If the entropy of a homogenized cell is used as a reference, the sum of all mixing entropies connected to the homogenization of the cell would define the boundary for the structural order of life
Summary
Among the many approaches to determine system complexity as a parameter, the idea originally developed by Andrey Nikolaevich Kolmogorov seems to be most appropriate to characterize life [1,2,3,4]. If we consider a living organism, serve as a rough representation of it could be of the size ofthen tensits or genome hundredsmay of Mbytes Organisms with smaller genomes may exist, but they just 490,885 base pairs, corresponding to 981,770 bits or, with one byte equal to eight bit, roughly are usually on close biomolecules in their environment or on other organisms, as insmaller case ofgenomes viruses. This may be to the lower limit of life’s complexity. This is at least a hundred times larger than the value for Nanoarchaeum equitans mentioned above
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