BISC 316 Lecture Notes - Lecture 2: Yoho National Park, Pikaia, Vertebral Column
11 Dec 2016
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Document Summary
Features of ancestral skeleton: notochord, vertebral column with skull. Living forms: fish, amphibians, reptiles, birds and mammals. <0. 1 gram (fish) 100,000 kg (blue whale) Characteristics of all 3 subphyla: pharyngeal slits. Opening in the wall of the pharynx (at least present in larval form) May not be present in adult form, however present at one point in their life. Made up of a fluid like substance. Muscle contraction of the notochord stiffens the body. Body (cid:373)o(cid:448)es for(cid:449)ard a(cid:374)d (cid:271)a(cid:272)k allo(cid:449)s (cid:373)o(cid:448)e(cid:373)e(cid:374)t si(cid:373)ilar to fish, as (cid:272)o(cid:373)pared to a worm: dorsal hollow nerve cord. Not present in adult urochordata: post-anal tail. Tail present in all embryos if not, at least present in adult form. Pharyngeal slits may be used for feeding. Highly vascularized tissue around pharyngeal slits where gas exchange occurs: notochord all embryos. Part of discs between vertebrae: single dorsal hollow nerve cord. Modified, widen to form the brain: post anal tail. Remnants present in all vertebrates: bilaterally symmetrical.
