In order to be effective competitors in the marketplace, students must be able to think critically, communicate complex ideas through writing, collaborate with peers, and apply their knowledge of biological science to generate solutions for issues facing society. In this paper we examine the nature of the instructional tools, strategies, and assessments we developed to convert a traditional senior-level biology course into a writing-intensive, capstone biology course. Key course objectives include (a) using writing as a learning strategy, (b) stimulating critical thinking through problem solving, (c) engaging students with primary scientific literature, (d) enhancing collaboration among students, and (e) using peer review and formative assessments to focus student thinking on learning and writing about biology. All students enrolled in the course are senior-level biology majors. Typically a third of our students plan to pursue a professional degree (veterinary, dental, or medical schools) and the remaining students plan to pursue an advanced degree in biology. The instructional strategies and assessments we developed will serve to inform others with the writing-intensive course design and assessments. (Contains 1 figure and 5 tables.)