Recommendations for enhancing scientific literacy, inclusivity, and the ecosystem for innovation call for transitioning from teacher-centered to learner-centered science classrooms, particularly at the introductory undergraduate level. Yet little is documented about the challenges that undergraduates perceive in such classrooms and the students' ways of navigating them. Via mixed methods, we studied undergraduates' lived experience in one form of learner-centered teaching, hybrid project-/problem-based learning (PBL), in introductory organismal biology at a baccalaureate institution. Prominent in qualitative analyses of student interviews and written reflections were undergraduates' initial expectation of and longing for an emphasis on facts and transmission of them. The prominence diminished from semester's middle to end, as students came to value developing ideas, solving problems collaboratively, and engaging in deep ways of learning. Collaboration and personal resources such as belief in self emerged as supports for these shifts. Quantitative analyses corroborated that PBL students transformed as learners, moving toward informed views on the nature of science, advancing in multivariable causal reasoning, and more frequently adopting deep approaches for learning than students in lecture-based sections. The qualitative and quantitative findings portray the PBL classroom as an intercultural experience in which culture shock yields over time to acceptance in a way supported by students' internal resources and peer collaboration. The findings have value to those seeking to implement PBL and other complex-learning approaches in a manner responsive to the lived experience of the learner.