In addition to the other provisions of this Charter, a vacancy shall be deemed to exist on any board or commission to which members are appointed for a specific term of office, when such board member fails to qualify within ten days after his appointment, fails to perform the duties of his office for a period of ninety days, dies, resigns, is removed from office, moves from the City, is convicted by a court of competent jurisdiction of a felony or of misconduct in office, or is judicially declared to be mentally incompetent.