Biological organisation

The simple standard biological organization scheme, from the lowest level to the highest level, is as follows: Each level in the hierarchy can be described by its lower levels. For example, the organism may be described at any of its component levels, including the atomic, molecular, cellular, histological (tissue), organ and organ system levels. Furthermore, at every level of the hierarchy, new functions necessary for the control of life appear. These new roles are not functions that the lower level components are capable of and are thus referred to as emergent properties. Every organism is organized, though not necessarily to the same degree. An organism can not be organized at the histological (tissue) level if it is not composed of tissues in the first place. ==Emergence of biological organization==

Biological organization is thought to have emerged in the early RNA world when RNA chains began to express the basic conditions necessary for natural selection to operate as conceived by Darwin (heritability, variation of type, and competition for limited resources). Fitness of an RNA replicator (its per capita rate of increase) would likely have been a function of adaptive capacities that were intrinsic (in the sense that they were determined by the nucleotide sequence) and the availability of resources. The three primary adaptive capacities may have been: (1) the capacity to replicate with moderate fidelity (giving rise to both heritability and variation of type). (2) the capacity to avoid decay. (3) the capacity to acquire and process resources. These capacities would have been determined initially by the folded configurations of the RNA replicators (see "Ribozyme") that, in turn, would be encoded in their individual nucleotide sequences. Competitive success among different RNA replicators would have depended on the relative values of these adaptive capacities. Subsequently, among more recent organisms competitive success at successive levels of biological organization, presumably continued to depend, in a broad sense, on the relative values of these adaptive capacities. == Fundamentals ==

Empirically, a large proportion of the (complex) biological systems we observe in nature exhibit hierarchical structure. On theoretical grounds we could expect complex systems to be hierarchies in a world in which complexity had to evolve from simplicity. System hierarchies analysis performed in the 1950s, laid the empirical foundations for a field that would be, from the 1980s, hierarchical ecology. The theoretical foundations are summarized by thermodynamics. When biological systems are modeled as physical systems, in its most general abstraction, they are thermodynamic open systems that exhibit self-organized behavior, and the set/subset relations between dissipative structures can be characterized in a hierarchy. A simpler and more direct way to explain the fundamentals of the "hierarchical organization of life", was introduced in Ecology by Odum and others as the "Simon's hierarchical principle"; Simon emphasized that hierarchy "emerges almost inevitably through a wide variety of evolutionary processes, for the simple reason that hierarchical structures are stable". == To motivate this deep idea, he offered his "parable" about imaginary watchmakers. ==