BIOL 2P92 Study Guide - Final Guide: Agnatha, Hydrostatic Skeleton, Endostyle
12 Apr 2016
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Chapter 15- vertebrate beginnings: the chordates: animals most familiar to people belong to phylum chordata, notochord, rod like structure extends in length of the body ventral to central nervous system, hydrostaic organ. Endostyle sessile: sessile as adults, divided into 3 classes, class ascidiacea. Few are sessile; atached to rocks (hard substrate: solitary or colonial ascidians = spherical/cylindrical. Lining tunic is mantle: outside has 2 projecions. Incurrent siphon: water enters incurrent siphon and passes into pharynx. Excurrent siphon: water exits through, nutrients absorbed in midgut & indigesible wastes discharged from anus, circulatory system consists of ventral heart, class appendicularia, class thaliacea. Early jawed vertebrates: jaw mouthed gnathostomes, monophyleic group, presence of jaws derived character state shared by all jawed ishes and tetrapods, without jaw agnathans, absence of jaws paraphyleic. Summary of taxonomy: phylum chordata, subphylum urochordata (tunicata) Notochord and nerve in free swimming larva only. Ascidian adults sessile: class ascidiacea, subphylum cephalochordata. Notochord + nerve cord enire length of body.
