Student motivation is widely regarded as an essential prerequisite for learning and success. To learn more about biology student motivation and how it changes over time, pre/post-surveys were administered to a large introductory biology course during the fall of 2015. These pre/post-surveys contained motivation subscales from the Intrinsic Motivation Inventory (IMI) and the Motivated Strategies for Learning Questionnaire (MSLQ). Although students began the course with high levels of motivation, the pre/post-survey scores revealed that their intrinsic motivation, self-efficacy, and value scores declined during the semester. The value/usefulness (IMI), pressure/tension (IMI), and test anxiety (MSLQ) pre-survey scores were the best predictors of course performance. The implications of these findings and suggestions for improving student motivation are discussed.