Experiences preservice teachers (PTs) have in their preparation programs can directly impact their use of effective and just pedagogy in the classroom (Darling-Hammond, 2000; Tolbert, 2015; Stoddart, Pinal, Latzke, and Canaday, 2002; Bravo, Mosqueda, Solis and Stoddart, 2014). However, researchers in the field of Education have struggled to make sense of the impact that teacher preparation programs have on teachers and their practice, particularly with respect to issues of diversity, equity, and justice in instructional theory and practice (Cochran-Smith et. al, 2015; Tolbert, 2016; Ladson-Billings, 1999; Waghorn and Stevens, 1996). This dissertation addresses the field's need for new analytics that can be used to gauge the actual, in-the-moment impact that equity-oriented teacher preparation activities have on preservice teachers' orientations with respect to students and equitable science instructional practices. This study employs a longitudinal case study design and Critical Cultural Discourse Analysis to investigate in depth how hegemonic power is enacted, resisted, challenged, and transformed in an equity-oriented science teacher preparation program (Creswell, 2014; Moje and Lewis, 2007; Gee, 2015; Fairclough, 1992). The analysis is guided by a critical sociocultural framework. My purpose was to add to our growing understanding of how systemic, structural, historical, and ongoing harm is sustained in and through equity-oriented science teacher preparation. Findings from this study reveal some of the ways in which hegemonic power acts in and through science teacher preparation. Through my analysis of two classroom discussions, I highlight Discourses of power that were enacted in/through the activity system. The first discussion, presented as Vignette I, concerned learning theories and their applications in science classrooms, and my analysis highlights the competing ideological and ontoepistemic assumptions embedded in the learning theories and Discourses. The second discussion, presented as Vignette II, centered on two preservice science teachers' reading of two articles on equitable science instruction. The PSTs' differing disciplinary discourse enactments engender a subtle tension, and the disciplinary literacy practices of western natural sciences enacted by one PST become an obstacle to sensemaking for the small group involved. My hope is that through building understanding of these issues, this study may generate new possibilities for reparation, care, and more just ways of being and learning in and beyond secondary science classrooms. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]