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and Oxygen (4.15%, 1.3% and 1.12%), respectively. The cOntributiOn Of Others is negligibly small.

Since the summary cOntributiOn Of hydrOgen, carbOn and silicOn is equal tO 96.2%, we can speak abOut Our biOsphere as the "hydrOgenOus -carbOnate-silicOn" biOsphere. If we cOmpare "carbOn exergy" Of 1 g Of living matter (106 J) and the sO-called "carbOn equivalent": ~ 8-9kJ/g Of raw biOmass, we can cOnclude that the part Of "structural", "creative" exergy is abOut 1.2%, i.e. it is very small in cOmparisOn with "heat" enthalpy. The latter is equal tO the number Of calOries Obtained in the prOcess Of biOmass burning.

In Chapter 5, a new measure Of exergy based On the genetic cOmplexity Of different Organisms was suggested. In accOrdance with this measure, if the "exergy cOst" Of detritus is equal tO 1, then the "exergy cOst" Of mOst plants and trees is abOut 30. NOte that glObal vegetatiOn is the leading actOr Of Our biOsphere. And if the free energy Of 1 g Of detritus is equal tO ~ 18.4 kJ/g, then the specific exergy Of living matter Of the biOsphere must be equal tO 550 kJ/g. There is a cOntradictiOn, is there nOt? How can we resOlve this?

The traces Of the past biOspheres are cOntained in the "stratOsphere" (a part Of the crust) that is created in the prOcess Of sedimentatiOn. It has accumulated sediments during the long time of evolution of the biosphere. Ronov (1980) estimates the total mass of organic carbon in the stratosphere as the value of ~ 1.2 X 1022 g, and the total mass of carbon in the contemporary biosphere is ~ 3 X 1018 g (Svirezhev et al., 1985). Note that we include in the biosphere not only the carbon of living matter, but also carbon of the atmosphere and pedosphere, since this carbon also participates in the "Small Carbon Cycle" connecting the atmOsphere, biOta and pedOsphere intO a single entity. Then the cOntempOrary value Of r = 2.5 X 10~4. Substituting the value into Eq. (7.2) we get that the specific exergy will be equal to ~ 520 kJ/g of living matter. Comparing this value with the "genetic" exergy we can see that they are very clOse.

Let us imagine the young biosphere, which is developed on the thin and young crust. This yOung biOsphere is very aggressive and all the crust matter is invOlved intO prOcesses Of chemical interactiOn and exchange with the biOsphere. Then, we get the case with r = 1, which was considered above, whereas the contemporary value of r = 3.6 X 10~6. This cOincidence seems tO be very interesting. NOte that the main cOntributiOn intO the specific exergy gives the term c0/r, i.e. the term corresponding to the processes working against the increase Of entrOpy, and that separate a thin film Of living matter frOm the immense mass of the crust. The latter, in turn, is the entropy storage of the past biospheres. It becOmes clear that the thinner this film, the better the ability Of the living matter tO dO this type Of wOrk. In Other wOrds, the smaller the value Of r, the larger the value Of specific exergy. But this situatiOn is typical fOr the Old biOsphere when it was in equilibrium a lOng time ago.

We see that the main rOle in the fOrmatiOn Of cOmparatively lOw exergy is played by the term KW (see Eq. (7.2)) determined by the chemical composition of living matter. In other wOrds, at the first stages Of the biOsphere fOrmatiOn the exergy Of living matter is determined mainly by its chemical cOmpOsitiOn and, as a cOnsequence, by the type Of chemical prOcesses used by life fOrms fOr the fOrmatiOn Of their matter.

11.8. Exergy and the evolution

The evolutionary paradigm is one of the main paradigms in ecology. It was already used in the previous section, when we estimated the exergy of living matter. Now let us consider how to apply the exergy concept to some evolutionary problem.

It is trivial that every point on the surface of our planet is different from any other point and therefore offering different conditions for the various life forms. This enormous heterogeneity explains why there are so many species on Earth (see also Section 4.7). There is, so to say, an ecological niche for "everyone", and "everyone" may be able to find a niche where the organism is best fitted to utilise the resources.

Ecotones, the transition zones between two ecosystems, offer a particular variability in life conditions, which often results in a particular richness of species diversity. Studies of ecotones have recently drawn much attention from ecologists, because ecotones have pronounced gradients in the external and internal variables giving a clearer picture of the relations between them.

Margalef (1991) claims that ecosystems are anisotropic, meaning that they exhibit properties with different values when measured along axes in different directions. It means that the ecosystem is not homogeneous in relation to properties concerning matter, energy and information, and that the entire dynamics of the ecosystem works toward increasing the differences.

These variations in time and space make it particularly difficult to model ecosystems and to capture the essential features of ecosystems. However, the hierarchy theory (Pattee, 1973) applies these variations to develop a natural hierarchy as a framework for ecosystem description and theory. The strength of the hierarchy theory is that it facilitates studies and modelling of ecosystems.

Darwin's theory describes the competition among species and states that the species best fitted to the prevailing conditions in the ecosystem will survive. Darwin's theory can, in other words, describe the changes in ecological structure and the species composition, but cannot be directly applied quantitatively, e.g. in ecological modelling (see Chapters 7-9, 12 and 13).

All the species in an ecosystem are confronted with the question: how is it possible to survive or even grow under the prevailing conditions? The prevailing conditions are considered as all factors influencing the species, i.e. all external and internal factors including those originating from other species. This explains the co-evolution, as now any change in the properties of one species will influence the evolution of the other species.

Species are generally more sensitive to stress than functional properties of ecosystems. Schindler (1988) observed in experimental acidifications of lakes that functional properties such as primary production, respiration and grazing were relatively insensitive to the effects of a continued exposure to acidification, while early signs of warning could be detected at the level of species composition and morphologies. This underlines the importance of the development of structurally dynamic models able to predict the change in focal properties of the species, which would correspond to a shift in species composition (see Chapter 13).

All natural external and internal factors of ecosystems are dynamic—the conditions are steadily changing, and there are always many species waiting in the wings, ready to take over, if they are better fitted to the emerging conditions than the species dominating under the present conditions. There is a wide spectrum of species representing different combinations of properties available for the ecosystem. The question is, which of these species are best able to survive and grow under the present conditions, and which species are best able to survive and grow under the conditions one time step further and two time steps further and so on? The necessity in Monod's sense is given by the prevailing conditions—the species must have genes or maybe rather phenotypes (meaning properties) which match these conditions to be able to survive. But the natural external factors and the genetic pool available for the test may change randomly or by "chance".

Steadily, new mutations (misprints are produced accidentally) and sexual recombinations (the genes are mixed and shuffled) emerge and steadily give new material to be tested against the question: which species are best fitted under the conditions prevailing just now?

These ideas are illustrated in Fig. 11.5. The external factors are steadily changing and some of them even relatively fast, partly randomly (e.g. the meteorological or climatic factors). The species of the system are selected among the species available and represented by the genetic pool, which again is slowly, but surely changing, randomly or by "chance". What is named ecological development is the changes over time in nature caused by the dynamics of the external factors, giving the system sufficient time for the

External factors Forcing functions

External factors Forcing functions

Ecosystem structure at time t + 1

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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