This paper explores how work in the philosophy of science can be used when teaching scientific content to science students and when training future science teachers. I examine the debate on the concept of fitness in biology and in the philosophy of biology to show how conceptual pluralism constitutes a problem for the conceptual change model, and how philosophical work on conceptual clarification can be used to address that problem. The case of fitness exemplifies how the philosophy of science offers (...) tools to resolve teaching difficulties and make the teaching of scientific concepts more adequate to the actual state of affairs in science. (shrink)