In the 1980s there was an intensification of research on the teaching knowledge base, with a configuration of typologies widely used today. Some of them have been the basis for the creation of specific and specialized theoretical models for different school subjects, pioneering in Mathematics. The objective of this research is to use the recent theoretical model of Biological Teachers 'Specialized Knowledge, the Biology Teachers' Specialized Knowledge - BTSK, as a tool for the analysis of practical biology classes on the respiratory system. We carried out a qualitative, interpretative investigation, whose data source was a report of teaching practice on the said Biology theme through the Repertoire of Professional and Pedagogical Experience - PaP-eR and we used the instrument of analysis of specialized knowledge (iMTSK) adapted to Biology. As a result, in addition to the characterizations of the mobilized knowledge, they were identified among the subdomains, identifying the specialized character and determining the legitimacy of BTSK as a tool for understanding and improving teacher training.