Any vacancy occurring in the board of directors and any directorship to be filled by reason of an increase in the number of directors may be filled by the board of directors unless the articles of incorporation or the bylaws provide that a vacancy or directorship so created shall be filled in some other manner, in which case such provision shall control. A director elected or appointed, as the case may be, to fill a vacancy shall be elected or appointed for the unexpired term of his or her predecessor in office.