Where Do Plants Get Their Mass From? Using Drawings to Assess Adolescent Students’ Modelling Skills and Their Ideas About Plant Growth

Abstract

AbstractThe purpose of this study was to explore the extent to which we could use student-constructed drawings to identify how students’ modelling skills evolve with age and how they relate to progress in their understanding of the mechanism of photosynthesis. Drawings are thought to complement the written text and oral discourse in revealing aspects of students’ understanding of biological processes. In addition, representing information in text and graphics has been identified as a productive strategy for the construction, refinement and evaluation of models. The study was conducted in three schools, with 75 students in grades 5, 7 and 10. The students responded to a questionnaire that consisted of two parts. In the first part, they answered questions about their individual experiences with plants, the processes involved in plant growth, and the role and value of plants in the earth’s ecosystem. In the second part, they were asked to develop a model in the form of a drawing answering the question “Where do plants get their mass from?” The students’ responses to both parts were analysed following a grounded theory approach, by following an iterative cycle of coding, code refinement and recoding. The responses were also scored for knowledge about plants and for three aspects of the modelling competence: representation of photosynthesising agents; illustration of the mechanism of photosynthesis; predictions with respect to environmental or other changes. Age/educational experience/maturation had an important influence on students’ responses and their drawings. Within each age group, we found that the more students knew about plants, the better their drawings worked as models of the process of photosynthesis. The responses also provide valuable information on the alternative conceptions held by students.