RESUMEN
This study examines how lower secondary school students understand the circulatory system, using the structure-behavior-function (SBF) framework for conceptual representation. It evaluates the progress of students' understanding after interventions with two different teaching approaches, one using a biology textbook supported by augmented reality (AR) technology and the other using only a textbook as a main source of information. The data analysis is based on the assumption that systemic understanding demands the perception of three system dimensions: the components forming the system at all levels of organization (its structures), the interactions and mechanisms between them (its behavior), and the function as a whole outcome (its phenomena). The results indicate that both learning approaches contribute to a higher level of understanding the circulatory system. The group using AR-supported educational materials showed statistically significant better improvements in their knowledge of the circulatory system, including all three components of the SBF framework.NEW & NOTEWORTHY This study examines how lower secondary school students understand the circulatory system, using the structure-behavior-function (SBF) framework for conceptual representation. It confirms that the use of augmented reality (AR) can help lower secondary school students understand the complexity of the circulatory system. The group using AR-supported instructional materials showed statistically significant better improvements in their knowledge of the circulatory system, including all three components of the SBF framework.