HIERARCHICAL ORGANIZATION OF BIOLOGICAL-SYSTEMS AND THE STRUCTURE OF ADAPTATION IN EVOLUTION AND TUMORIGENESIS

Biological systems are structurally organized according to patterns re peated at each hierarchical level. Complex units are composed of so-ca lled interactors, systems that by cooperative interaction maintain the structure of the complex unit. Interactors are composed of large numb ers of assemblies of complex units of a limited number of types of a l ower hierarchical level. Thus, macromolecules, cells, organisms and ec ological communities should be defined as complex units, and cellular organelles, organs and oligospecies populations as the interactors bet ween those units. The similarity of organization at each level should make it possible to describe patterns of structure at one level and ap ply it to organization at another level. This was tested for the struc tural aspects of adaptation as viewed in a pathobiological context. Ad aptation is then viewed as the result of stress seen at the level of t he interactors or st the level of the lower complex units related to t he type of stress. Subsequently, this structure of adaptation was appl ied to adaptation in biological evolution and tumorigenesis, which has led to the conclusion that stress is a driving force for both and tha t an increase in number of organisms or cells may precede heritable ch anges or mutations, respectively. (C) 1997 Academic Press Limited.