ABSTRACT
If we accept the general proposition or basic philosophy that life evolves as a hierarchical system, then it is convenient to consider properties of biosystems in terms of levels of organization—viz., genes, cells, organs, organisms, populations, communities, ecosystems, and so on (see, for example, Grobstein, 1969; Odum, 1975a, 1975b; Redfield, 1942). Some properties of living systems, and the methods applicable to their study, are especially relevant, or perhapseven unique, to particular levels of organization in the hierarchy. For example, birth rate is a functional property more appropriate to the population level of study than to the organism or community level. Other properties “emerge” as smaller units are integrated into larger systems, which is to say that the forest (as an ecosystem) has characteristics in addition to those of the trees (as component populations). Fiebleman (1954) has suggested that at least one major emergent property can be expected with each successive level in the hierarchical series. Still other properties are perhaps applicable over a wide range of levels. I believe diversity is a general systems property that is important at most, if not all, levels of biological Organization. Thus, we can consider as an important property the diversity of antibodies in an immune system as well as the diversity of species in an ecosystem.
