Same; members, term, eligibility, appointment; vacancies; removal, manner. The board of supervisors shall, at its next regular or special session, after the adoption of this act in any county, appoint, by a majority vote of the members-elect, 3 electors of the county as members of the civil service commission to take office as soon as appointed and qualified, and who shall serve for the following terms as designated in the resolution of appointment: One member for a term expiring 2 years from December 31 of that year, 1 member for a term expiring 4 years from December 31 of that year, and 1 member for a term expiring 6 years from December 31 of that year. Thereafter the board of supervisors shall biennially, at either the October or April session of that board, appoint by majority vote 1 civil service commissioner for a term of 6 years to take office on January 1 of the next year and succeed the commissioner whose term shall next expire. The commissioner whose term shall next expire shall serve as chairman of the commission. Any vacancy occurring on said commission shall be filled for the unexpired term by the board of supervisors by a majority vote of the members-elect. Each commissioner shall serve until his successor is appointed and qualified. No commissioner shall hold any other public office, except that of notary public, or be employed by the county or any other governmental agency, or any board, commission or department thereof in any other capacity. Each commissioner shall have been a resident of the county for 5 years next preceding his appointment and shall be an elector of the county. One commissioner shall be appointed from the county seat or the metropolis of the county, 1 commissioner shall be appointed from outside the county seat or metropolis, and the third member shall be appointed by reason of his knowledge of or experience in employment methods. Not more than 2 of the commissioners so appointed shall be members of the same political party. Two members of the commission shall constitute a quorum thereof. The board of supervisors by a 2/3 vote of all the members-elect may remove a commissioner during his term of office, but only after serving such commissioner with a statement in writing of the reasons for such removal, and allowing him an opportunity to be represented and publicly heard in his defense.