Stability (resistance to external perturbations)
Ecological buffer capacity
The information content increases in the course of ecological development because an ecosystem integrates all the modifications that are imposed by the environment. Thus, it is against the background of genetic information that systems develop which allow interaction of information with the environment. Herein lies the importance in the feedback organism-environment, that means that an organism can only evolve in an evolving environment, which in itself is modifying. The differences between the two stages include entropy and eco-exergy.
The conservation laws of energy and matter set limits to the further development of "pure" energy and matter, while information may be amplified (almost) without limit. Limitation by matter is known from the concept of the limiting factor: growth continues until the element which is the least abundant relatively to the needs by the organisms is used up. Very often in developed ecosystems (for instance an old forest) the limiting elements are found entirely in organic compounds in the living organisms, while there is no or very little inorganic forms left in the abiotic part of the ecosystem. The energy input to ecosystems is determined by the solar radiation and, as we shall see later in this chapter, many ecosystems capture —75-80 percent of the solar radiation, which is their upper physical limit. The eco-exergy, including genetic information content of, for example, a human being, can be calculated by the use of Equations 6.2 and 6.3 (see also Box 6.3 and Table 6.3). The results are —40MJ/g.
A human body of —80 kg will contain —2 kg of proteins. If we presume that 0.01 ppt of the protein at the most could form different enzymes that control the life processes and therefore contain the information, 0.06 mg of protein will represent the information content. If we presume an average molecular weight of the amino acids making up the enzymes of — 200, then the amount of amino acids would be 6 X 10~8 X 6.2 X 1023 /200 « 2 X 1017, that would give an eco-exergy that is (10~5 moles/g, T = 300K, 20 different amino acids):
= 8.314 X 80,000 X 300 X10~5 X 2 X1017 ln 20 = 1.2 X1012 GJ
It corresponds to 1.5 X 107 GJ/g. These are back of the envelope calculations and do not represent what is expected to be the information content of organisms in the future; but it seems possible to conclude that the development of the information content is very, very far from reaching its limit, in contrast to the development of the material and energy relations (see Figure 6.1).
Information has some properties that are very different from mass and energy.
(1) Information unlike matter and energy can disappear without trace. When a frog dies the enormous information content of the living frog may still be there a microseconds after the death in form of the right amino-acid sequences but the information is useless and after a few days the organic polymer molecules have decomposed.
(2) Information expressed for instance as eco-exergy, it means in energy units, is not conserved. Property 1 is included in this property, but in addition it should be stressed that living systems are able to multiply information by copying already achieved successful information, which implies that the information survives and
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