This paper presents a case study of the student`s culture as a component of conceptual ecology that affects discussions and discourses in the science classroom. The present study was conducted using a naturalistic approach, mainly through observing a science class of a middle school in Seoul, Korea, and through semi-structured interviews. The case showed that the science classroom culture can be identified in four aspects: (1) knowledge; (2) the teacher; (3) classmates; and (4) self. These cultural aspects were strongly related to each other and functioned as constraints in discussions and discourses of the science classroom. For successful discussions and discourses, it is necessary to consider students` cultural aspects: epistemological views on knowledge, the teacher-student and student-student relationships, and the role of self in the discussions and discourses.