<P> Pharyngeal slits are filter - feeding organs found in Invertebrate chordates ( lancelets and tunicates ) and hemichordates living in aquatic environments . Pharyngeal slits are repeated openings that appear along the pharynx caudal to the mouth . With this position , they allow for the movement of water in the mouth and out the pharyngeal slits . It 's postulated that this is how pharyngeal slits first assisted in filter - feeding , and later with the addition of gills along their walls , aided in respiration of aquatic chordates . These repeated segments are controlled by similar developmental mechanisms . Some hemichordate species can have as many as 200 gill slits . Pharyngeal slits resembling gill slits are transiently present during the embryonic stages of tetrapod development . The presence of gill - like slits in the neck of the developing human embryo famously led Ernst Haeckel to postulate that `` ontogeny recapitulates phylogeny '' ; this hypothesis , while false , contains elements of truth , as explored by Stephen Jay Gould in Ontogeny and Phylogeny . However , it is now accepted that it is the vertebrate pharyngeal pouches and not the neck slits that are homologous to the pharyngeal slits of invertebrate chordates . Gill slits are , at some stage of life , found in all chordates . One theory of their origin is the fusion of nephridia which opened both on the outside and the gut , creating openings between the gut and the environment . </P>
<P> Pharyngeal slits are filter - feeding organs found in Invertebrate chordates ( lancelets and tunicates ) and hemichordates living in aquatic environments . Pharyngeal slits are repeated openings that appear along the pharynx caudal to the mouth . With this position , they allow for the movement of water in the mouth and out the pharyngeal slits . It 's postulated that this is how pharyngeal slits first assisted in filter - feeding , and later with the addition of gills along their walls , aided in respiration of aquatic chordates . These repeated segments are controlled by similar developmental mechanisms . Some hemichordate species can have as many as 200 gill slits . Pharyngeal slits resembling gill slits are transiently present during the embryonic stages of tetrapod development . The presence of gill - like slits in the neck of the developing human embryo famously led Ernst Haeckel to postulate that `` ontogeny recapitulates phylogeny '' ; this hypothesis , while false , contains elements of truth , as explored by Stephen Jay Gould in Ontogeny and Phylogeny . However , it is now accepted that it is the vertebrate pharyngeal pouches and not the neck slits that are homologous to the pharyngeal slits of invertebrate chordates . Gill slits are , at some stage of life , found in all chordates . One theory of their origin is the fusion of nephridia which opened both on the outside and the gut , creating openings between the gut and the environment . </P>
what is the function of pharyngeal pouches in aquatic chordates
what is the function of pharyngeal pouches in aquatic chordates
filter - feeding respiration of aquatic chordates
filter - feeding respiration of aquatic chordates