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…