Level of Organization

: Scientific knowledge is organised in levels, not because reduction in principle is impossible, but because nature is organised in levels, and the pattern at each level is most clearly discerned by abstracting from the detail of the levels far below. [. . .] And nature is organised in levels because hierarchic structures – systems of Chinese boxes – provide the most viable form for any system of even moderate complexity. — Herbert A. Simon ('The Organisation of Complex Systems’ in "Hierarchy Theory: The Challenge of Complex Systems", 1973, p. 26)

In the first chapter of their book "The Superorganism", Bert Hölldobler and E.O. Wilson provide an elegant description of life as a scale-free hierarchy of biological complexity:

: "Life is a self-replicating hierarchy of levels. Biology is the study of the levels that compose the hierarchy. No phenomenon at any level can be wholly characterized without incorporating other phenomena that arise at all levels. Genes prescribe proteins, proteins self-assemble into cells, cells multiply and aggregate to form organs, organs arise as parts of organisms, and organisms gather sequentially into societies, populations and ecosystems. Natural selection that targets a trait at any of these levels ripples in effect across all the others."