Case of the study is physics education in upper secondary education in the Netherlands since 1970. The study examines the extent to which teachers' current practices, the enacted curricula, reflect key ideas from the curriculum renewals of the past decades. It also examines what factors contributed to these ideas, called curriculum intentions, being expressed in the implemented curricula. This perspective is inspired by ecology and evolution theory. Curriculum intentions are considered memes, which, like genes, are units of information and can be expressed in written and implemented curricula over decades. In interviews, teachers indicate how they express most of the curriculum intentions studied. Professional development, a resource-rich environment, and mobility between different roles of stakeholders, such as member of a renewal commission, author, teacher educator, researcher, or teacher, appear to increase the "contagion rate" of curriculum intentions between teachers and developers.