This paper explores affordances in teaching evolution, especially those in which evolution is made relevant to and argued for in a grade 9 biology classroom, thus giving potential answers to the pupils' legitimate question,"'why am I learning evolution?" The aim of the paper is methodological in the sense that it explores whether the notions "subject focus," "curriculum emphasis" and "intertextuality" have potential as analytical tools and pointers towards enacted scientific literacy in classroom practice. The notion of subject focus (either induction into science or learning from science) and the seven curriculum emphases (correct explanation, structure of science, scientific skill development, solid foundation, everyday coping, decision making and self as explainer) are predefined and used abductively on the data set. Intertextuality is analysed more inductively: references that pupils and teacher make are sought and these intertextual links are then sorted into clusters. The findings indicate that the structuring tools have potential as descriptors in the analysis. One subject focus (induction into science) and a few curriculum emphases (especially correct explanations) are privileged, while others, "eg" everyday coping, are not. When the discourses of self as explainer and correct explanations compete, it is the latter that is privileged.