The talk will describe the nature of biology's resources and why ontologies are needed. It will briefly describe our favoured knowledge representation language, DAML+OIL, and its capabilities. The principal of these are its expressiveness and its reasoning support, which allow sound and complete maintenence of the concept lattice and post co-ordinated use of the resulting ontology. The speaker will talk about some of the problems of modelling the biological domain, before describing the use of DAML+OIL in two bioinformatics modelling projects. The first, the Gene Ontology Next Generation (GONG), takes a well established community-generated, hand-crafted phrase-based ontology and uses DAML+OIL to add rigour and completeness to its representation. GONG demonstrates how the reasoning support on offer with DAML+OIL allows improved management and building of ontologies. the second project, the myGrid Bioinformatics Services Ontology, shows how the reasoning services can allow dynamic, post co-ordinated construction of partial or complete description on the fly. The reasoning service can then be used to place the new description correctly within the lattice of concepts. In myGrid, this DAML-S based description of bioinformatics services is used to describe and retrieve instances of bioinformatics services from a service repository. the ontology, together with the reasoner and the service repository form the basis of a discovery service.