This chapter shall enable, authorize, and empower the governing body of any city having the requisite number of inhabitants to adopt a civil service system adapted to the size and    requirements of the city. Such system, if deemed advisable by such body, may consist merely in the setting up of minimum employment qualifications for full-time members of the city’s paid fire and police departments and the heads thereof with provisions prohibiting their suspension, removal, or discharge, or the suspension, removal, or discharge of any other appointive employee or official except upon adequate reason and cause shown upon hearing and thereon after reasonable notice to the person or persons sought to be suspended, removed, or discharged. If deemed advisable by the governing body, the civil service system may consist of a comprehensive system covering all paid fire and police department full-time employees and the heads of these two departments and other appointive full-time employees and officials, other than common laborers and employees who have not been in the continuous employment of the city for a period of more than one year, as in the discretion of the governing body of the city may be for the best interests of the public, such employees, and the service to be rendered to the city.