Learning difficulties resulting from students holding conceptions of scientific concepts which are at variance with those presented in curricular materials have been identified in the literature in a number of areas of science. In this study a number of student learning difficulties related to the concepts of growth and the cell were identified. More specifically, this study was designed to investigate whether alternative conceptions held by students prior to instruction were, in part, responsible for these learning difficulties. The study also investigated whether omissions in instruction contributed to these learning difficulties. Finally, the study examined changes in student conceptions after formal instruction. Through concept analyses of growth and the cell, two semi-structured interview protocols were developed. The Growth Protocol was used to interview students in Grades 3, 5, and 7 and the Cell Protocol was used to interview students in Grade 10. The students in Grades 3 and 10 were interviewed both before and after instruction. The conceptions of the students identified in the transcripts were classified into a number of categories specific to the constituent concepts of growth and the cell. Students at all grade levels were found to hold a wide variety of alternative conceptions regarding the concepts in question. The majority of these alternative conceptions were identified in more than one student and did not reflect current scientific or curricular understandings of growth or the cell. Rather, it seemed that these alternative conceptions reflected student attempts to make sense of concrete experiences with phenomena in their surroundings. After instruction at both the elementary and secondary level, the majority of students did not incorporate most of the scientific concepts as they were presented during instruction. The older students did not hold a conception of cell differentiation nor did the majority of students link the microscopic phenomena of cell division with the macroscopic phenomena of growth in organisms other than humans. The variability of alternative conceptions of mitosis and meiosis after instruction strongly suggested that the students experienced learning difficulties with respect to these concepts. The results of this study imply that in order to effectively move the learner from alternative conceptions to scientific conceptions both curricular and instructional strategies must shift their emphasis from one of presenting only disciplinary knowledge to one of considering also the prior knowledge that the learner brings to the instructional setting. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate