Each state and major mainland territory has its own parliament — unicameral in the Northern Territory, the ACT and Queensland, and bicameral in the other states. The states are sovereign entities, although subject to certain powers of the Commonwealth as defined by the Constitution. The lower houses are known as the Legislative Assembly (the House of Assembly in South Australia and Tasmania); the upper houses are known as the Legislative Council. The head of the government in each state is the Premier and in each territory the Chief Minister. The Queen is represented in each state by a governor; and in the Northern Territory, the administrator. In the Commonwealth, the Queen's representative is the governor-general.