There shall be a Scottish Parliament.

One member of the Parliament shall be returned for each constituency (under the simple majority system) at an election held in the constituency.

Members of the Parliament for each region shall be returned at a general election under the additional member system of proportional representation provided for in this Part and vacancies among such members shall be filled in accordance with this Part.

The validity of any proceedings of the Parliament is not affected by any vacancy in its membership.

Schedule 1 (which makes provision for the constituencies and regions for the purposes of this Act and the number of regional members) shall have effect.