Chapter 19 Lecture

Chapter 19 Lecture - 1 Chapter 19 The Evolution of...

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1 Chapter 19 Chapter 19 The Evolution of Vertebrate Diversity 2 Figure 19.0_2 3 4 VERTEBRATE EVOLUTION AND DIVERSITY 5 19.1 Derived characters define the major clades of chordates ± Biologists have developed hypotheses for the evolution of chordate groups using –ana tom ica l , – molecular, and – fossil evidence. ± Figure 19.1 – illustrates a current view of the major clades of chordates and – lists some of the derived characters that define the clades. 6 7 19.2 Hagfishes and lampreys lack hinged jaws ± Hagfishes and lampreys – are craniates, – have a notochord, but – lack hinged jaws and paired fins. ± Lampreys but not hagfishes have rudimentary vertebral structures. Thus, – lampreys are vertebrates but – hagfishes are not vertebrates. 8 19.2 Hagfishes and lampreys lack hinged jaws ± Hagfishes are deep-sea scavengers that produce slime as an antipredator defense. ± Lamprey adults are parasites that penetrate the sides of fishes with their rasping tongues. ± Larval lampreys – resemble lancelets and – are suspension feeders that live in freshwater streams, where they feed, buried in sediment. 9 10 11 19.3 Jawed vertebrates with gills and paired fins include sharks, ray-finned fishes, and lobe-finned fishes ± Jawed vertebrates – appeared in the fossil record about 470 million years ago and – quickly diversified using their paired fins and tail to chase a wide variety of prey. ± Jaws may have evolved by modifications of skeletal supports of the anterior pharyngeal (gill) slits. ± The remaining gill slits remained as sites of gas exchange.
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± Three lineages of jawed fishes with gills and paired fins are commonly called fishes: 1. chondrichthyans—sharks and rays, 2. ray-finned fishes—tuna, trout, and goldfish, and 3. lobe-finned fishes—coelacanths and lungfishes. 14 19.3 Jawed vertebrates with gills and paired fins include sharks, ray-finned fishes, and lobe-finned fishes ± Chondrichthyans have – a flexible skeleton made of cartilage, – electrosensors on their heads, and –a lateral line system that helps them locate prey. – Most sharks are fast-swimming predators, with sharp vision and a keen sense of smell. – Most rays are adapted for life on the bottom, with dorsoventrally flattened bodies and eyes on the top of their heads. 15 16 17 19.3 Jawed vertebrates with gills and paired fins include sharks, ray-finned fishes, and lobe-finned fishes ± Ray-finned fishes have – an internal skeleton reinforced with a hard matrix of calcium phosphate, – flattened scales covered with mucus, – an operculum that covers a chamber of gills, and – a buoyant swim bladder (derived from an ancestral lung). ± With more than 27,000 species, ray-finned fishes are the most diverse group of
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This note was uploaded on 11/06/2011 for the course BIOL 1402 taught by Professor Atanasov during the Fall '08 term at Texas Tech.

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Chapter 19 Lecture - 1 Chapter 19 The Evolution of...

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