This unit addresses the political organization of the world. Building on knowledge of populations and cultural patterns learned in previous units, students examine the contemporary political map and the impact of territoriality on political power and on issues of identity for peoples. Students also look at the different types of political boundaries, how they function, and their scale, as they consider both internal and international boundaries. The interplay of political and cultural influences may cause tensions over boundaries to arise, such as sovereign states making claims on what other states consider to be international waters. Students also examine forms of government and how forces such as devolution may alter the functioning of political units and cause changes to established political boundaries. Separatist and independence movements that challenge the sovereignty of political states may arise from economic and nationalistic forces, as seen in Scotland, Northern Ireland, and Spain. The influence of supranational organizations such as the United Nations or European Union and their role in global affairs presents another challenge to nationalist sovereignty. Student understanding of cultural patterns and processes helps inform their understanding of the consequences of centrifugal and centripetal forces.