Constructing scientific explanations of natural phenomena is an important aim of science education. Explanation oriented science teaching approaches encourage learners to engage in sense-making discussions and construct the causal accounts of the phenomena under study. This article demonstrates a lesson-design model that guides biology teachers on how to integrate explanation oriented teaching in their everyday practice. The proposed model includes six phases: (1) presenting a hooking activity; (2) formulating a how-why type focus question; (3) constructing the initial causal story; (4) using authentic data, scientific facts, principles, and disciplinary core ideas to revise-refine the causal story; (5) discussing-rewriting the refined causal story; (6) applying the causal-mechanistic knowledge in a new context or problem scenario. An eleventh-grade lesson on the topic 'protein biosynthesis in cells' serves an example about how this model can be operationalized to design and implement explanation oriented biology lessons.