Photosynthesis is the predominant metabolic process for energy obtention in plants. Here we describe a case study where a set of anatomical, biochemical, and molecular characters are used to reconstruct the evolution of the C[subscript 4] photosynthetic pathway, within the evolutionary framework provided by the genus "Flaveria." Our main educational goal was to engage biology undergraduate students to solve a photosynthesis-related phylogenetic problem by stimulating them to assemble informative characters of diverse nature. This case study was successfully implemented as a seminar in a massive university introductory course, during the COVID19 lockdown. Using an online learning environment, most small groups achieved the Students Learning Outcomes, which were assessed through a questionnaire and an open-ended question. Individual performance was also evaluated through a specific exercise in the course's midterm test. Finally, students were surveyed for their perception about the seminar through a poll. We concluded that this seminar could be easily adopted to promote the learning of complex and interdisciplinary content like the C[subscript 4] photosynthetic pathway in undergraduate botanical education, even in a large online introductory course.