Dusko --
BTW have you seen the book:
Life Itself. A Comprehensive Inquiry Into the Nature, Origin, and Fabrication of Life by Robert Rosen (Columbia University Press 1991)
it was referenced in a biology paper, i found it in the biology library, and it's full of categories. (yes, i kno, people often do that to sound complicated, but this seems like honest work, perhaps even inspiring, although it does not go very deep.)
An earlier book of Rosen's applying category theory to biology (or rather, speaking more carefully, exploring how one might conceive of applying category theory to biological domains) was: "Anticipatory Systems: Philosophical, Mathematical and Methodological Foundations" (Pergamon Press, Oxford, UK 1985) You may also be interested in this work by Andree Ehresmann and Jean-Paul Venbremeersch on a category-theoretic account of evolving systems, such as those found in biological domains: http://perso.wanadoo.fr/vbm-ehr/ Peter McBurney Department of Computer Science University of Liverpool