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Lecture25_AnimalsIII - B the limb C the amniotic egg •...

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Animals III I. Overview of deuterostomes two key phyla: echinoderms and chordates A. Echinoderms (“spiny skins”) 1. Examples: 2. What makes an echinoderm an echinoderm? • Water vascular system • endoskeleton: • metamorphosis: • bilaterally symmetric larvae; B. Chordates 1. Examples (“subphyla): 2. What makes a chordate a chordate? Notochord present, at least in embryo Pharyngeal gill slits Central nervous system with dorsal nerve cord A tail that extends past the anus
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Phylogeny of chordates (ascidians, tunicates) Echinoderms Xenoturbellida Urochordates Vertebrates Hemichordates Cephalochordates notochord, dorsal nerve cord, muscular post-anal tail II. Key innovations in vertebrate evolution A. The jaw Hypothesis: the vertebrate jaw evolved from gill supports in jawless fish What is the adaptive significance of the jaw? Key innovations in the transition to land
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Unformatted text preview: B. the limb C. the amniotic egg • membrane-bound water supply • tough, waterproof outer shell Fish eggs = What is the adaptive significance of the amniotic egg? Which lineages of vertebrates are most species-rich? Clade # species Hagfish and lampreys ………………………… 80 Sharks, rays, skates …………………………. . 900 Ray-finned fish …………………………… Lobe-finned fish ………………………………. 7 Amphibians (frogs, toads, salamanders) … 4200 Turtles …………………………………………… 260 Snakes and lizards ……………………………. Crocodiles ……………………………………… 22 Birds ……………………………………………… Mammals ………………………………………… 4500...
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Lecture25_AnimalsIII - B the limb C the amniotic egg •...

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