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Phylum Chordata. Phylum Chordata. common characteristics segmented muscles ventral heart complete digestive system. Five defining chordate characteristics pharyngeal gill slits dorsal, hollow nerve cord post anal tail e ndostyle /thyroid gland notochord.
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Phylum Chordata common characteristics segmented muscles ventral heart complete digestive system • Five defining chordate characteristics pharyngeal gill slits dorsal, hollow nerve cord • post anal tail • endostyle/thyroid gland notochord
Body Structure post-anal tail pharyngeal slits & atriopore Notochord with myomeres dorsal, hollow nerve cord
SubphylumUrochordata (Tunicates) “tail string” Adult Larva • all are filter feeders • sessile & pelagic; solitary & colonial • tadpole-like larva
Three Classes • Ascidiacea • Larvacea • Thaliacea
Class Ascidiacea “sea squirts” • u-shaped gut, with incurrent oral and excurrent atrial siphons • large central chamber (atrium)
Subphylum Cephalochordata “head string” Lancelets (Amphioxus) • burrow into sand & shell gravels • filter feeders
Closed Circulatory System • flow pattern similar to fishes • no “heart” • peristaltic contractions of blood vessels
Phylum Chordata Subphylum Vertebrata • larval notochord replaced by vertebral column in adults • dorsal nerve cord • pharyngeal gill slits
Trends in Vertebrate Evolution • Living Endoskeleton • Pharynx and Efficient Respiration • Advanced Nervous System • Paired Limbs
Early Chordata Fossils • Pikaia • Resembles Amphioxus • Distinct notochord • Chevron shaped muscle