There has been much attention about improving the skills and abilities of students in Science. One critical factor is the quality of teacher education programs for preparing science teachers. There has been little research and much debate about what constitutes an effective science teacher education program. Teacher beliefs are thought to be important factors which influence how science teachers teach. This is a three year longitudinal study which explores changes in twelve teachers using a mixed method design. Semi-structured interviews were used to explore the beliefs about teaching, learning, and the Nature of Science. Four cohorts of teachers represented the different critical stages of the teaching continuum. Two cohorts of teachers represented entry and exit stages of preservice education. The other two cohorts represented teachers who taught less than four years and more than four years in the classroom. Classroom observations and self-reported surveys were gathered. The major outcomes of this research include: (1) Teacher beliefs about teaching and learning shift towards being more student-centered during their preservice education; (2) Despite previous reports that most graduates revert to teacher-centered beliefs in the first years of teaching, the beliefs of Iowa preservice teacher beliefs, remained similar to their previous student-centered beliefs; (3) Teacher beliefs about the Nature of Science, which were initially represented as a socially constructed entity, became less frequent as 2 teachers progress through the teaching continuum from preservice to inservice teachers; (4) Student-centered beliefs about teaching and learning, derived from teacher interviews, are correlated with classroom observations and self-reported surveys of instructional strategies. The findings from this study shed light on understandings concerning the evolution of teacher beliefs. Factors effecting teacher beliefs include college preparatory education programs, school communities, and the individual teachers themselves. There is a need to continue explorations of how these factors are interrelated, as well as how to influence and sustain the development of reformed-based beliefs about teaching and learning in order to influence instructional practices. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]