Welcome to the Energy in the Human Body Curriculum Project. Alternative conceptions (misconceptions) abound in science at all age levels including the very young, teenagers, and adults. Since students' initial ideas are often based on personal experiences occurring in the real world, individuals frequently develop mental models as well as beliefs and attitudes that are not scientifically accurate (not compatible with currently accepted theories). While these individuals may function well with naïve or alternative models about some concepts, such as electricity or relative motion, reliance on inaccurate models for biological concepts may be cause for more concern. One such area where alternative and naïve conceptions are common is the study of the human body and specifically, respiration and the flow of energy in the body. For example, it is possible that these inaccurate models could interfere with students' selection of healthy habits particularly in the area of tobacco use. In addition, an understanding of human respiration is necessary for children to relate issues in the world around them to their own health such as the effect of pollution and diseases of other body systems like asthma, heart disease, diabetes, and cancer. Researchers report that as many as three thousand teenagers begin to smoke each day. Yet when asked to explain what effects smoking had on their bodies, our research showed that teenagers were able to do little more than repeat pat phrases they had been told by authorities such as "turns your lungs black." Unfortunately, beyond these statements their ability to explain why or how smoking is dangerous was rarely apparent. Because we believe youth need and want to take responsibility for their own bodies and their health, we feel it is important to find better ways to help them construct mental models of their bodies that they can use to reason about their world. That is the purpose of this curriculum. It is the result of almost eight years of research on how middle school students learn. In addition, new teaching strategies for helping students in the difficult process of constructing mental models of complex topics have been developed. We hope you will find it useful both in teaching this curriculum and in other areas as well.