In any city of the first class except any city having adopted the commissioner or city manager plan of government, the mayor and city council members shall be registered voters of the city and the city council members shall be residents of the ward from which elected if elected by ward and residents of the city if elected at large. The city council may also, by a two-thirds vote of its members, provide by ordinance for the election of the treasurer and clerk. All nominations and elections of such officers shall be held as provided in the Election Act. The terms of office of all such members shall commence on the first regular meeting of the city council in December following their election.