Using UML, can we model life itself with everything in it?

UML Class Diagrams can express hierarchical ontologies, and associations.

Upper Ontologies are intended to model all entities that can be hierarchically related. So if you’re ambitious enough (see: Douglas Lenat), upper ontologies can model life itself with everything in it; and associations can model (at least at first approximation) all relations between with everything within life.

So yeah, sure.

That’d be an awfully big wallpaper diagram though…