The animals need to get close enough to the vents to feed on chemosynthetic bacteria, which derive nourishment from the energy-rich 
(The animals; need; to get close enough to the vents to feed on chemosynthetic bacteria) (The animals; to get; close enough to the vents to feed on chemosynthetic bacteria) (chemosynthetic bacteria; derive; nourishment; from the energy-rich)
The animals The animals chemosynthetic bacteria
need to get derive
to get close enough to the vents to feed on chemosynthetic bacteria
close enough to the vents to feed on chemosynthetic bacteria
nourishment from the energy-rich