The present paper delves into the classroom dynamics of Biology classrooms taking into account teaching learning processes associated with some of the ethical issues in Biological Sciences. Argumentation and debate appear to be the major transactional approaches adopted by teachers for dealing with these issues. The classroom discourses emanating from teacher student conversations have been analysed on four planes, viz., ethical, social context, interactional context and personal agency of the teacher. Toulmin's method of argument analysis has been used in order to analyse the level of arguments of both teachers and their students. The findings reveal significant differences on all the four planes at K-12 and Undergraduate levels and, have implications for building upon teachers' pedagogical content knowledge (PCK) with respect to ethical issues.