(a) The board of directors shall consist of one or more members. The number of directors constituting the board may be fixed by the by-laws, or by action of the shareholders or of the board under the specific provisions of a by-law adopted by the shareholders. If not otherwise fixed under this paragraph, the number shall be one. As used in this article, "entire board" means the total number of directors which the corporation would have if there were no vacancies.

(b) The number of directors may be increased or decreased by amendment of the by-laws, or by action of the shareholders or of the board under the specific provisions of a by-law adopted by the shareholders, subject to the following limitations:

(1) If the board is authorized by the by-laws to change the number of directors, whether by amending the by-laws or by taking action under the specific provisions of a by-law adopted by the shareholders, such amendment or action shall require the vote of a majority of the entire board.

(2) No decrease shall shorten the term of any incumbent director.