a^-Value for mammals is 2127 and for grass is 200.
a^-Value for mammals is 2127 and for grass is 200.
equilibrium; If more combinations and processes are offered to utilize the Exergy flow, the organization that is able to give the highest Exergy under the prevailing circumstances will be selected. This hypothesis may be reformulated, as proposed by de Wit (2005) as: If a system has a throughflow of free energy, in combination with the evolutionary and historically accumulated information, it will attempt to utilize the flow to move further away from the thermodynamic equilibrium; if more combinations and processes are offered to utilize the free energy flow, the organization that is able to give the greatest distance away from thermodynamic equilibrium under the prevailing circumstances will be selected.
Both formulations mean that to ensure the existence of a given system, a flow of energy, or more precisely Exergy, must pass through it, meaning that the system cannot be isolated. Exergy may be seen as energy free of entropy (Jorgensen, 1997; Jorgensen and Marques, 2001), i.e. energy which can do work. A flow of Exergy through the system is sufficient to form an ordered structure, or dissipative structure (Prigogine, 1980). If we accept this, then a question arises: which ordered structure among the possible ones will be selected or, in other words, which factors influence how an ecosystem will grow and develop? The difference between the formulation by exergy or eco-exergy and free energy has been discussed in Chapter 6.
Jorgensen (1992b, 1997) proposed a hypothesis to interpret this selection, providing an explanation for how growth of ecosystems is determined, the direction it takes, and its implications for ecosystem properties and development. Growth may be defined as the increase of a measurable quantity, which in ecological terms is often assumed to be the biomass. But growth can also be interpreted as an increase in the organization of ordered structure or information. From another perspective, Ulanowicz (1986) makes a distinction between growth and development, considering these as the extensive and intensive aspects, respectively, of the same process. He argues that growth implies increase or expansion, while development involves increase in the amount of organization or information, which does not depend on the size of the system.
According to the tentative Ecological Law of Thermodynamics, when a system grows it moves away from thermodynamic equilibrium, dissipating part of the Exergy in cata-bolic processes and storing part of it in its dissipative structure. Exergy can be seen as a measure of the maximum amount of work that the ecosystem can perform when it is brought into thermodynamic equilibrium with its environment. In other words, if an ecosystem were in equilibrium with the surrounding environment its exergy would be zero (no free energy), meaning that it would not be able to produce any work, and that all gradients would have been eliminated.
Structures and gradients, resulting from growth and developmental processes, will be found everywhere in the universe. In the particular case of ecosystems, during ecological succession, exergy is presumably used to build biomass, which is exergy storage. In other words, in a trophic network, biomass, and exergy will flow between ecosystem compartments, supporting different processes by which exergy is both degraded and stored in different forms of biomass belonging to different trophic levels.
Biological systems are an excellent example of systems exploring a plethora of possibilities to move away from thermodynamic equilibrium, and thus it is most important in ecology to understand which pathways among the possible ones will be selected for ecosystem development. In thermodynamic terms, at the level of the individual organism, survival and growth imply maintenance and increase of the biomass, respectively.
From the evolutionary point of view, it can be argued that adaptation is a typically self-organizing behavior of complex systems, which may explain why evolution apparently tends to develop more complex organisms. On one hand, more complex organisms have more built-in information and are further away from thermodynamic equilibrium than simpler organisms. In this sense, more complex organisms should also have more stored exergy (thermodynamic information) in their biomass than the simpler ones. On the other hand, ecological succession drives from more simple to more complex ecosystems, which seem at a given point to reach a sort of balance between keeping a given structure, emerging for the optimal use of the available resources, and modifying the structure, adapting it to a permanently changing environment. Therefore, an ecosystem trophic structure as a whole, there will be a continuous evolution of the structure as a function of changes in the prevailing environmental conditions, during which the combination of the species that contribute the most to retain or even increase exergy storage will be selected.
This constitutes actually a translation of Darwin's theory into thermodynamics because survival implies maintenance of the biomass, and growth implies increase in biomass. Exergy is necessary to build biomass, and biomass contains exergy, which may be transferred to support other exergy (energy) processes.
The examples of industrial melanism in the peppered moth and warning coloration and mimicry are compliant with the Ecological Law of Thermodynamics, illustrating at the individual and population levels how the solutions able to improve survival and maintenance or increase in biomass under the prevailing conditions were selected. Also, the adaptations of Darwin's finches to take advantage of feeding in different ecological niches constitute another good illustration at the individual and population levels. Depending on the food resources available at each niche, the beaks evolved throughout time to be best suited to their function in the prevailing conditions, improving survival, and biomass growth capabilities. Finally, the horses' lineage increase in size illustrates very well how a bigger weight determines a decrease in body specific surface and consequently a decrease in the direct loss of free energy (heat loss by respiration). From the thermodynamic point of view, we may say that the solutions able to give the highest exergy under the prevailing circumstances were selected, maintaining or increasing gradients and therefore keeping or increasing the distance to thermodynamic equilibrium.
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Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.