Joint approaches of sciences and mathematics learning by experimental approaches Gilles Aldon, Réjane Monod-Ansaldi & Michèle Prieur IFÉ-ENS de Lyon S2HEP, Université Lyon 1 gilles.aldon@ens-lyon.fr, rejane.monod-ansaldi@ens-lyon.fr, michele.prieur@ens-lyon.fr Abstract : In inquiry based approaches in sciences, mathematics is usually present but often ignored or underestimated. Mathematical knowledge can be identified at different levels to allow teachers and students to become aware of the implementation of this knowledge in scientific work. Building on observations made under the project "Development of scientific culture, equal opportunities" in schools of the city of Dijon, we derive a typology characterizing the role of mathematics in science courses at different levels . We show through examples that it is possible to mobilize mathematical knowledge at various levels to conduct scientific approaches and give meaning to the mathematical knowledge mobilized. Résumé : Dans les démarches d'investigation en sciences, les mathématiques sont généralement présentes mais souvent ignorées ou sous-estimées. Les savoirs mathématiques peuvent être convoqués à des niveaux différents qu'il s'agit d'identifier et de définir pour permettre aux enseignants et aux élèves de prendre conscience de la mise en œuvre de ces savoirs dans un travail scientifique. En nous appuyant sur des observations réalisées dans le cadre du projet “Développement de la culture scientifique, égalité des chances” conduit dans des écoles de la ville de Dijon, nous dégageons une typologie caractérisant la place des mathématiques dans le cours de sciences à différents niveaux. Nous montrons alors sur des exemples qu'il est possible de mobiliser les savoirs mathématiques à des niveaux divers pour conduire des démarches scientifiques et donner du sens aux connaissances mathématiques mobilisés. Introduction In inquiry based learning in sciences, mathematics is usually present but often ignored or underestimated. Whether mathematical knowledge can be used at different levels, it is often difficult to identify for students and for teachers where this knowledge is available in scientific work. In this communication we will show where and how it is possible to construct mathematical knowledge in such inquiry based learning process. This work draws on observations and analysis made in the context of the project “Développement de la culture scientifique, égalité des chances” ("Development of scientific culture, equal opportunities") , where teachers and researchers work in a design-based research methodology (Wang & Hannafin, 2005). Such a methodology enables us to build usable and useful resources by combining scientific approaches and problematics coming from teachers. In this paper we will describe the context and will show how mathematics can be a part of the construction of scientific methodologies and, reciprocally, how scientific approaches can give opportunities to learn mathematics and to build mathematical knowledge. Experiencing on living organisms in primary school The teaching curriculum in French primary schools in sciences involves the discovery of living beings and the study of their functioning. These requirements in terms of content and methods lead teachers and students to conduct experimental procedures on living organisms, especially involving growing plants. But, what are the characteristics of experiments on living things? Living organisms have characteristics that affect their study in experimental biology. Indeed, due to size, variability and complexity, conceptualization and modeling of living matter is difficult (Coquidé et al, 1999). Already in 1965, Canguilhem (Canguilhem, 1965) drew attention to