How does Macbeth express the span of life?
While Macbeth follows the tragic arc it also serves as a microcosm for life's cycle. After all, Macbeth means "Son of Life."
Birth: birth imagery is threaded throughout the play. Lady Macbeth has had miscarriages, leaving the couple childless. She says she would dash her baby's brains out and trade her mother's milk for gall. Macduff was "none of woman born." He was untimely ripped from his dead mother's womb.
Childhood: again more imagery here. Macbeth fears children throughout the play: Duncan's, Banquo's, and Macduff's. Mostly, he fears Banquo's child, Fleance, and future children, as they will be kings. Macbeth kills the father, but the child escapes. Macbeth does kill Macduff's child, but for no reason.
Marriage: we have two sets of marriages in the play: the Macbeths and the Macduffs. In both, there is division. After the Macbeth's conspire and kill Duncan, they stop communicating and effectively divorce. The Macduff's too differ on the role of the husband. Lady Macduff calls Macduff a traitor to the family because he puts the plight of Scotland above their protection.
Old age: Duncan, the old king, is murdered by the young thane. See the conversation the Old Man has with Lennox in Act II, scene iv:
Time is a major theme in the play, and the Old Man cannot remember when he's seen such unnatural acts. It's as if the Old Man is living in another time.
Death: there is death in every act. Before we even meet Macbeth, we hear of him killing. He kills Duncan in Act II, Banquo in Act III, the Lady Macduff in Act IV, and young Siward in Act V. Plus, he and his wife obviously die. His famous soliloquy on Tomorrow sums up his view of life and death.
Afterlife: Macbeth is a very Christian play, and there is much allusion to Christian concepts (Virgin Birth, Heaven and hell imagery, and Christ figures [Macduff])