Biological systems are often described using hierarchical language: lower and higher levels, more basic and more advanced forms, or processes that build upward from simple to complex.
APS treats this as a modelling convenience, not a feature of reality.
In place of hierarchy, APS uses the concept of scale. Biological organisation unfolds across continuous, interacting spatial and temporal scales, with no intrinsic ranking of “higher” or “lower.” What appear as levels are regions of relative stability within a dynamically coupled system.
This shift matters because hierarchical language can imply that some processes are more fundamental than others, or that explanation proceeds in a single direction. APS instead emphasises reciprocal, scale-coupled organisation, where causation and regulation operate across interacting domains.
Key Point. Biological organisation varies in form across scales, not in rank within a hierarchy.