Biology is often introduced as a hierarchy:
molecules → organelles → cells → tissues → organs → organisms → populations → communities → ecosystems
This ordering can be useful for describing composition, containment, and spatial organisation. Cells can form tissues, tissues can form organs, and organisms participate in populations and ecological communities. APS does not reject these biological relations.
What APS rejects is the assumption that this descriptive ordering automatically constitutes an explanatory hierarchy.
A biological explanation does not necessarily proceed from one level to the next, nor does a wider spatial extent automatically provide a more complete explanation than a narrower one. The relations relevant to a biological question may extend across several spatial and temporal extents, while remaining materially implemented through the biological processes involved.
APS therefore treats Scale as an analytic projection, not as a hierarchy of biological levels.
Scale asks:
Across what spatial and temporal extents is persistence organised?
The answer depends on the explanatory problem. A particular phenomenon may require attention to molecular interactions, cellular organisation, organismal activity, environmental relations, developmental time, evolutionary history, or some combination of these. These extents do not form a predetermined ladder of explanatory importance.
Key Point. The familiar biological hierarchy can be useful for describing how biological entities are arranged. APS does not treat that arrangement as an explanatory hierarchy. Scale identifies the spatial and temporal extents across which the organisation relevant to a particular biological question must be traced.