Pre-service teachers‟ first experiences and ideas prior to application affect their teaching activities. For this reason, it is aimed to determine transferring the experiences and ideas of prospective science teachers before lesson activities and its development with lesson activities. The study was carried out with 29 third year prospective teachers who attended the course named Laboratory Application II and undergraduate students at the Department of Science Education at Karadeniz Technical University during 2012-2013 spring semesters. The study was conducted by case study design. Thirty-minute lesson activities were carried out by them. Reflective writings constituted by candidates, lesson observations and plans were used as data collecting tools. They were examined through inductive thematic analyze. When compared before and during lesson activities process, it was determined that pre-service teachers‟ perception, ideas or application had changed at some concepts. This case might be a proof of development of pre service teachers‟ professional skills doing practice.