Biological organisation should not be confused with biological structure. Structures are materially real and indispensable to living systems, but a description of their arrangement at a particular time does not by itself explain how a living system continues to function. Many apparently stable biological structures persist only because ongoing activity produces, maintains, repairs, regulates, or replaces their material constituents.
Biological organisation concerns these continuing activities and dependencies: the materially realised relations through which structures and processes contribute to maintaining and re-establishing the conditions of continued functioning. Organisation can therefore remain continuous even when particular structures, materials, and configurations change. This does not make structure secondary or unimportant; it means that structural invariance is not sufficient to explain biological continuity.
Understanding biological organisation therefore requires more than identifying what structures are present. It requires explaining the materially realised dependencies through which structures and activities participate in the continuing organisation of the living system.