Recent discourse analytic studies indicate that rhetoric in academic writing (both experts and students) differs across disciplines. This study explores the use of introductions and conclusions written by second-year undergraduate students in examination essays from the departments of English, Sociology, and Zoology, at a Ghanaian public university, using a modified version of Swales' rhetorical model. This textual data is supplemented by interview and observation of classroom interactions. The analysis of these two key rhetorical units revealed some similarities and differences with respect to frequency,distribution, and sequencing of moves. In addition, there were notable lexico-grammatical features in the moves identified. Moreover, English and Sociology exhibited some differences in both the moves and linguistic features across the two rhetorical units. These findings have important implications for studies in disciplinary discourse, writing pedagogy and future research in disciplinary rhetoric at the undergraduate level.