Morphology concerns the form and structural configuration of biological systems and structures.
In conventional biology, morphology encompasses the description and comparison of anatomical form, structural features, spatial arrangement, and related characteristics. Such description can be explanatory in combination with other evidence, but morphology itself should be distinguished from the processes responsible for generating or transforming the form described.
APS preserves this distinction. Morphological form can be characterised at a particular time without assuming that form is static in a stronger biological sense. Structures may arise, persist, change, or disappear during development and other biological processes, and explaining those changes requires identifying the relevant processes and dependencies.
Morphological description may concern, depending on the biological target:
- anatomical structure,
- tissue organisation,
- body architecture,
- spatial differentiation,
- structural pattern,
- proportions,
- topology,
- and other features of biological form.
These features are morphological because they characterise form or structural configuration, not because they necessarily contribute to viability or organised persistence.
Morphology is historically and developmentally situated in the sense that present form can result from earlier biological processes. Morphogenesis, developmental regulation, physiological activity, mechanical conditions, environmental relations, or other processes may contribute to the production or transformation of particular morphological features where the relevant dependencies are present.
Those causal relations should not be built into the definition of morphology itself. A morphological feature may contribute to viability, persistence, behaviour, ecological interaction, or adaptation, but it may also be neutral or adverse with respect to those outcomes. Its biological significance must therefore be established for the case concerned.
APS distinguishes morphology from morphogenesis. Morphology refers to biological form or structural configuration; morphogenesis refers to the developmental processes through which form is generated, maintained, or reorganised. Description of a form and explanation of its production are related but distinct explanatory tasks.
The spatial extent relevant to morphology is likewise target-dependent. Some morphological questions concern relatively local structures, while others concern relations among tissues, organs, whole organisms, or other biologically relevant configurations. The presence of structural relations over different extents does not make morphology intrinsically multiscale.
APS therefore does not treat morphology either as a merely static object or as viability-oriented persistence expressed in structural form. Morphology identifies biological form; its developmental origins, organisational significance, functional consequences, and relations to viability, persistence, ecology, behaviour, adaptation, and scale are further explanatory questions.
Key point: morphology is biological form and structural configuration. What produces that form, what it contributes to, and over what spatial or temporal extent it must be explained depend on the biological system and explanatory target concerned.