biol_119__lecture_6__9-14-09

biol_119__lecture_6__9-14-09 - Lecture 6, 9-14-09 •...

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Unformatted text preview: Lecture 6, 9-14-09 • Review class today from 3:30 to 4:20 Arrange the following traits to reflect an accepted sequence in phylogeny 1. Notochord 3. Cranium 2. Vertebral column 4. Ancestral deuterostome A. 4, 1, 2, 3 B. 1, 3, 2, 4 C. 2, 3, 4, 1 D. 4, 1, 3, 2 E. 4, 3, 1, 2 B. Fossils of Early Vertebrates • Conodonts (cone teeth) were among the first vertebrates (Figure 34.11) • With mineralized skeletal elements in their mouth and pharynx Continuing our look at vertebrates after lampreys (Petromyzontida) • Vertebrates with further innovations were soon to follow: paired fins, a muscular pharnyx and mineralized bone . The first bone did not appear in the endoskeleton but was actually an exoskeleton of bony plates (these armored fish were called ostracoderms). • However, these jawless, armored vertebrates went extinct • They were replaced by vertebrates having a mineralized endoskeleton C. Origins of Bone and Teeth • Mineralization appears to have originated with vertebrate mouthparts as seen on the conodont dental elements • The armor ( exoskeleton ) seen in later vertebrates was derived from dental mineralization. • Ths same mineralization that was present in the mouth eventually was transferred to the vertebrate endoskeleton which became fully mineralized much later, starting with the skull Concept 34.4: Gnathostomes are vertebrates that have jaws • Around 360 million years ago, gnathosomes largely replaced the the jawless (agnatha) fish. • Chondrichthyes (the cartilaginous fishes), Osteichthyes ( bony fishes), and the extinct placoderms evolved during this time. • Today, jawed vertebrates far outnumber those without jaws (hagfish and lampreys) A. Derived Characters of Gnathostomes • Gnathostomes have jaws that evolved from skeletal supports of the anterior pharyngeal gill slits Mouth Gill slits Cranium Skeletal rods Figure 34.13 • Jaws and two pairs of fins were two major evolutionary improvements found in these fish. • Jaws, with the help of teeth, enable the animal to grip food items firmly and slice them up.. • Paired fins, along with the tail, enable fishes to maneuver accurately while swimming. • Other characters common to gnathostomes include • Enhanced sensory systems, including the lateral line system • An extensively mineralized endoskeleton Mineralization of bone appears to have first begun in teeth, T or F? B. Fossil Gnathostomes • The earliest gnathostomes in the fossil record are an extinct lineage of armored vertebrates called placoderms (Figure 34.14) C. Chondrichthyans (Sharks, Rays, and Their Relatives) • This is our first class of existing Gnathostomes • Members of class Chondrichthyes have a skeleton that is composed primarily of cartilage • According to some scientists, the cartilaginous skeleton is thought to have evolved secondarily from an ancestral mineralized skeleton making the cartilaginous skeleton of these fishes a derived characteristic, not a primitive one. •...
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This note was uploaded on 05/04/2011 for the course BIO 119 taught by Professor O'donnellandspear during the Spring '07 term at SUNY Geneseo.

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biol_119__lecture_6__9-14-09 - Lecture 6, 9-14-09 •...

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