Hierarchical organization of biological systems and the structure of adaptation in evolution and tumorigenesis.

Biological systems are structurally organized according to patterns repeated at each hierarchical level. Complex units are composed of so-called interactors, systems that by cooperative interaction maintain the structure of the complex unit. Interactors are composed of large numbers of assemblies of complex units of a limited number of types of a lower hierarchical level. Thus, macromolecules, cells, organisms and ecological communities should be defined as complex units, and cellular organelles, organs and oligospecies populations as the interactors between those units. The similarity of organization at each level should make it possible to describe patterns of structure at one level and apply it to organization at another level. This was tested for the structural aspects of adaptation as viewed in a pathobiological context. Adaptation is then viewed as the result of stress seen at the level of the interactors or at the level of the lower complex units related to the type of stress. Subsequently, this structure of adaptation was applied to adaptation in biological evolution and tumorigenesis, which has led to the conclusion that stress is a driving force for both and that an increase in number of organisms or cells may precede heritable changes or mutations, respectively.