BISC 1112 Chapter Notes - Chapter 34: Tiktaalik, Hagfish, Myllokunmingia
31 Mar 2017
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Cambrian period: 530 million years ago; introduction of vertebrates. 365 million years ago: evolution of limbs in one lineage of vertebrates allowed their colonization. Introduction of land (before, for 150 million years, were restricted to water) Vertebrates have large disparity: variation between the species. 34. 1: chordates have a notochord and a dorsal, hollow nerve cord. All chordates share a set of derived characteristics. Notochord: longitudinal, flexible rod located between the digestive tube and the nerve cord; skeletal structure. In humans, reduced and forms part of gelatinous disks sandwiched between the vertebrae. Made of large fluid-filled cells encased in fairly stiff tissue. Dorsal, hollow nerve cord of chordate develops from plate of ectoderm that rolls into a tube located dorsal to the notochord. Develops into central nervous system: brain and spine. Other animal phyla have solid nerve cord. Pharyngeal clefts: grooves that separate the arches of the outer surface of the pharynx. Develop into pharyngeal slits that open into the pharynx.
