This poster reports from an ongoing developmental research project in which mathematical modelling tasks are introduced to biology students as a means of motivating them to engage more deeply in mathematical studies. In the present report the focus is on how the mathematical discourse of the students develops as they participate in the project. Data consisting of video recordings of four modelling sessions comprising both group work and whole-class discussion will be analysed using commognitive theory. Data collection is still ongoing, and no analyses have been conducted as yet, but preliminary observations indicate cases of commognitive conflict, as the students struggle to adapt to a mathematical discourse still unfamiliar to them.