Final answer:
The perforated pharynx of chordates first evolved as a device for filter-feeding.
Step-by-step explanation:
The perforated pharynx of chordates first evolved as a device for filter-feeding. In organisms that live in aquatic environments, pharyngeal slits allow for the exit of water that enters the mouth during feeding. Some invertebrate chordates use the pharyngeal slits to filter food out of the water that enters the mouth.