 These recent trends towards intertwining, rather than separating, the concepts of development and evolution is in contrast to authoritative voices in evolutionary biology (and to a substantial part in philosophy of biology) during most of the twentieth century (see Sapp 1983; Burian 2004; Amundson 2005). As a consequence of this tradition, this new integration faces a number of conceptual and methodological challenges. In this entry, the focus will be on debates associated with the relationship between development and evolution. Other discussions about what each of the two components, development and evolution, are or how they are (or should be) conceptualized or studied individually is only addressed when relevant to this main topic. 