During the last three decades, earth science has been re-conceptualized as an interdisciplinary discipline entitled Earth System Science (ESS), which is based on knowledge of the physical earth system and human impact on the earth. While there is increasing effort to teach earth as a system in K-12 education, teachers' preparedness of to teach earth system is still in its infancy. This article focuses on reviewing the literature of teachers' knowledge of earth systems and of how teachers' knowledge of subject matter affects their teaching practice and pedagogical content knowledge (PCK). First, the study investigated a literature of PCK in general as well as in science teaching. Then this study duscuss what teachers' subject matter knowledge (SMK) is and what it means to be in teaching earth system science. Third, a literature of teachers' knowledge of earth system was reviewed. Finally, a number of suggestions and implications are made as to what teacher education program should do to better prepare future teachers to teach earth systems.

There has been increasing evidence of the positive effects in informal science programs to promote the youths' positive development. However, relatively a small number of informal science programs target specific student populations such as youth in poverty with little research done about the important program factors. This case study presents an exemplary informal science education program (focusing on Earth Science Education or more specifically, water in urban environments) for youth in poverty in a midwest city of the United States. This study explored the most important characteristics of the program that could lead to positive development for the youth. Through a number of observations of the program and interviews with the participants, this study employs inductive and interpretive research methods. Findings show that the program managers' beliefs about the youths' knowledge and experiences, their relationship building skills, and their cooperative work are very important. A concrete mission for the program and structured institutional support to hire the youth as paid museum staff are also important in assuming their responsibility and building identity as an active social member.

This study presents how a professional development program (PD) of K-12 teachers affects participants' use of the earth system approach and their perceptions of using the urban environment for their science teaching and lesson unit development. This study utilized mixed methods to collect and analyze the data. Eleven urban teachers' pre-post lessons (45 lessons) were analyzed quantitatively using a lesson plan analysis tool, modified by the author, and their lesson reflections were analyzed qualitatively. The findings of this study show that the PD program influences the teachers to choose more topics and content knowledge based on the earth system approach and to assess the topics and content knowledge with more appropriate methods. Specifically, the teachers use more urban environmental factors/topics in their post lesson to teach the environmental topics of urban area. However, according to the statistical analysis of pre-and postlesson plan scores, the accuracy of the earth system knowledge that participants used in their lessons did not change significantly (p〈0.05) (Table 4), which means that the PD program did not affect the improvement of the teacher's content knowledge in earth system science. Implications of this study are discussed.