This paper explores classroom discourse patterns of lessons on topics perceived to be difficult in biology such as classification, mitosis and meiosis at senior secondary school level. A collective case study design was used and data were obtained from pupils and teachers using observation schedules and interview guides. Data collected were analysed using discourse analysis and thematic analysis. The study found that three discourse patterns are used by teachers when teaching topics perceived to be difficult in biology. These discourse patterns include teacher explanation discourse pattern, teacher led discourse pattern and pupil to pupil discourse pattern. The effects of these discourse patterns are that pupils and teachers find it difficult to explain stages of cell division and classification of living organisms. In view of the findings above, the following recommendations are made; Teachers should combine the three discourse patterns when teaching topics perceived to be difficult in biology. Teachers should avoid teaching using one discourse pattern when teaching topics perceived to be difficult in biology. Workshops and seminars should be organised for teachers in order for them to improve their skills on the use of these three discourse patterns.