The legislative power of the city shall be vested in a city council which shall be a continuing body consisting of 3 members at large and one member from each of such even number of wards which shall be established by council by ordinance enacted not later than January 15 of the year in which the first election for members of council from wards as established by such ordinance is to be held.
   Councilmen shall be elected under this charter at the regular municipal election to be held in the year 1973 and at each subsequent regular municipal election to succeed those whose terms will expire at the conclusion of the year in which such election is held as hereinafter provided.
   The term of office of each member of the council shall begin on January 1 next following his election. Councilmen-at- large shall serve for terms of 4 years each and ward councilmen shall serve for terms of 2 years each, or until their respective successors are chosen and qualified, except that of the members elected at large in 1973, the 2 receiving the largest number of votes shall serve for terms of 4 years and the remaining one shall serve for a term of 2 years.