The council shall appoint five park commissioners, a board of health consisting of three members, a city planning commission, and may appoint a radio commission, an airport commission, and such other boards and commissions as it may deem necessary. They shall be appointed by the council by ballot, and the affirmative vote of three members shall be necessary for such appointments. The park commissioners shall hold their offices for five years and until their successors shall have been appointed and qualified. The members of the board of health shall be appointed annually. The duties of the various boards and commissions shall be fixed by the council by ordinances. All present members shall hold office until their respective term expires.