Background: Video lectures which include the teachers' presence have become increasingly common. As teacher enthusiasm is a nonverbal cue in video lectures, more and more studies are focusing on this topic. However, little research has been carried out on the interactions between teacher enthusiasm and prior knowledge when learning from video…

This study examines how a first-year biology teacher facilitates a series of whole-class discussions about evolution during the implementation of a problem-based unit. A communicative theoretical perspective is adopted wherein evolution discussions are viewed as social events that the teacher can frame intellectually (i.e., present or organize as…