The project we report from in this paper explores whether and how, biology students’ competence and confidence in – as well as appreciation for – mathematics in their discipline can be improved through greater integration of mathematics and biology in their study programme. Here, we examine biology students’ mathematical discourse as they engage with a biology-related Mathematical Modelling (MM) activity, the Digoxin task. We report commognitive analyses of data collected during sessions in which biology-related MM activities were introduced to undergraduate biology students (four sessions with 12 first-semester students).We focus on the interplay between students’ ritualised and exploratory engagement with the activity, particularly concerning graphing routines, and consider pedagogical implications.