Colleges and universities across the country use active learning to enhance student understanding of biology content knowledge. Active learning is both a style of teaching and way of learning that encourages students to engage with their instructors and peers to solve problems, explore ideas, and apply concepts to real-world settings. Studies have shown that active learning is more effective at improving students’ understanding of core concepts across STEM fields when compared to traditional lecture-based instruction. While there has been widespread adoption of active learning, little is known about the specific mechanisms that contribute to its effectiveness. The importance of this project is that it intends to define instructor and student behaviors and interactions across biology active learning classrooms and how these aspects of the course learning environment shape students’ understanding of biology content. Using video, survey, and interview data from a national sample of biology classrooms, the significance of this research is that it could result in practical guidance for instructors on how to support active learning in their classrooms This project goals include the identification of latent behavioral and social characteristics of biology active learning environments and how they impact students’ understanding of core biology concepts. In Aim One, course video data collected from a national sample of large introductory biology courses with various learning ins