Teachers' subject matter knowledge is a substantive component of the teaching-learning process. For a teacher to be able to transform and integrate into the classroom all the knowledge and experience they have acquired in the course of the professional activity, it is first necessary to acquire a deep and solid knowledge of the matter. The aim of the research was to analyse the understanding that pre-service teachers have about the physiology and anatomy of the human body. The alternative conceptions that pre-service teachers held about the nutritional function in living beings were also explored. The research was conducted on a biology course of the Primary Education Bachelor’s Degree during the 2018/2019 academic year. Drawings and open-ended questions were collected from 96 pre-service teachers. The results reveal that the students surveyed have limited knowledge of the subject before entering university. The use of drawing proved to be an excellent tool for detecting previous conceptions and evaluating the progression made by the students in their learning. Numerous alternative conceptions were identified among the students, thus demonstrating the need to think about the scientific methodology used to teach these contents.
