This study investigated the characteristics students use in attributing value to and classifying the living things; the relational construction of the life concepts and the living things and the place of human in this construction. Participants were first-year high school students from seven schools in Izmir (a large western city in Turkey). An open-ended conceptual understanding test was developed and administered to students. Semistructured interview forms were applied to students and biology teachers, one from each school; and this provided additional data to clarify ambiguous points in students’ responses to the conceptual test. Results revealed that students constructed the life concept by associating it predominantly with ‘human’. The most frequently associated concept to the life concept was found to be motion. Students tended to use their own classification criteria instead of biological classification. Generally, we noticed classifications in the form of ‘human-animal-plant’