The bassist simply repeats this and variations of throughout the whole song.  The timing
isn't exact, but if you just listen to the song, you'll be able to do it.  I think this
is the easiest way to play this piece for bass.  Thanks and have fun learning this great 
bass piece.

Tuning is standard bass tuning
G |----------------------------------------------------|
D |--------------------0-0-0---------------------------|
A |----------------0-2-------0-2---2-0-----------------|
E |-0--0-0--2-3-3----------------0-----3-2-0-----------|

G |------------------------------------------------------|
D |--------------------0-0-0-----------------------------|
A |----------------0-2-------0-2-2-2---------------------|
E |-0--0-0--2-3-3--------------------3-2-0---------------|