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Download Deuterostomate Animals
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The Deuterostomes • • • • Embryonic blastopore becomes the anus. Three body layers. True coelom. Dorsal nerve cord. Phylum Echinodermata • Spiny exterior • Calcified internal skeleton • Bilateral symmetry in larvae, but often radial symmetry in adults • Water vascular system for mobility, gas exchange, and feeding. – system of internal tubes and canals – tube feet that can exert strong suction Phylum Chordata • • • • • Pharyngeal slits (gill slits in neck) Ventral heart Post-anal tail Hollow dorsal nerve cord Dorsal supporting rod, the notochord – A solid rod of tissue, NOT equivalent to backbone Many of these may become obscure, modified, or absent in later development of the organism. Invertebrate Chordates No vertebral column (i.e. no true backbone) • Tunicates (subphylum Urochordata) – tadpole-like larva has chordate features; adults are sessile • Lancelets (subphylum Cephalochordata – fish-like; notochord throughout life Vertebrates (Subphylum Vertebrata) • Notochord disappears, and is replaced by vertebral column (articulated bones) • two pairs of appendages • anterior skull • well-developed circulatory system – closed system (blood leaves heart and returns to heart in closed vessels; never pumped into open body cavity) Jawless fishes Class Agnatha Hagfish Lampreys Class Chondrichthyes Cartilaginous fishes Sharks, Rays, and Skates Bony fishes: Class Osteichthyes (includes ray-finned fish, lobe-finned fish, and lungfish) The Coelecanth, a lobe-finned fish Amphibia Moist skin Eggs laid in water; External fertilization Aquatic larvae with gills metamorphose into air-breathing adults Amniote Egg • • • • • Allows fully terrestrial life. Waterproof shell. Reservoir of water inside the egg. Fertilization is internal, before the shell forms. (Later, some amniote animals evolved the ability to retain the egg internally, never developing a shell, and giving birth to live young.) • Other features of Amniote animals: – Waterproof skin – Ability to excrete concentrated urine, in order to conserve water.
