Question

What are pharyngeal gill slits.?

Answer 1

Pharyngeal gill slits are a chordate feature; these are openings between the pharynx to the outside. They have been modified hin the time of evolution.

In primitive chordates, these slits are used to filter food particles from the water. In fishes and some amphibians, the slits bear gills and are used for gas exchange.

=> In most land- living chordates, the "gill slits" are present only in embryonic stages; that is we had pharyngeal slits at one time.
The slits are supported by gill arches, which have also been highly modified in various groups of vertebrates.