As academic organisers and teachers with different positions teacher training programs at Södertörn University we have had the opportunity to develop and assess different types of pedagogic activities and use, e.g., the 4 R´s proposed by Doll, recursion, relations, richness, and rigor in assessments. Here pre-service teacher student reflections assessed by use of the 4R’s are compared with other texts by the same students in order to assess the quality of their understanding of evolutionary theory. Written performances of biology students are also compared with those of pre-service teacher students in order to reveal differences in the use of scientific concepts between the groups. Analysis of student performances show a relation between the use of the 4R’s, and the use of scientific concepts. Analyses of texts by students in evolution theory show a relatively low use of scientific concepts often regarded as important in scientific text. This may be explained by students’ good skills in giving scientific explanations in every-day language. Teacher students used more biological and evolutionary concepts compared to biology students. The emphasis on the use of concepts, especially in school, may be exaggerated. Professional biologists have to communicate with people outside the scientific community but teachers often cares about a strict scientific language. This is also found here where teacher students use the concepts to a larger extent than biology students. School biology should focus on the basic processes of organic evolution as the foundation of all teaching in order to enhance the students’ deeper understanding.