usually the serp. belt will shed because it shifts on one of the ridged pulleys. The most common cause of this is a failing pulley or a bad tensioner.
the belt is ether too old, or a faulty component that is being driven by the belt.
Check the allignment of all the pully's.
it could be a serpentine belt or accessory belt.
No, an accessory belt is not considered a serpentine belt. However, a serpentine belt is considered a specific type of accessory belt.
If it's a "chirping" noise, then you don't have the belt tight enough.
The serpentine belt would be the same as the accessory drive belt.
Serpentine Belt Diagram ML320
Serpentine belt, no. Timing belt, good chance yes.
If the alternator belt is the same belt as the other accessories, yes.
Almost every car ever will not start without a serpentine belt. The serpentine bell acts similarly to a pulley. It's movement causes everything else to rotate and move. If you look at an engine, there's a number of circular shapes where the serpentine belt goes. It uses traction to rotate them.
Old age Frozen or misaligned pulley
That I know of, there is NO serpentine belt, unless you are talking about the the Timing Belt (hardly serpentine, but anyway), it has a belt tensioner, not automatic, though.