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Hemichordata and Chordata Are Two Deuterostome Phyla

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Hemichordata and Chordata Are Two Deuterostome Phyla Hemichordata and Chordata are two Deuterostome phyla. Along with the phylum Echinodermata, Hemichrodata and Chordate belong to a common ancestor. Both hemichordates and chordates are coelomates. Class Enteropneusta • Acorn worms-named so b/c of the proboscis at the anterior end • 75 species, 10-40 cm usually • Most occupy U-shaped burrows along the sandy shore-line • Cilia and a mucous-covered proboscis assist in feeding Class Pterobranchia • Name means “wing or feather gills” • Around 20 species-Rhabdopleura • Small-0.1-5 mm, often living in secreted tubes in asexually produced colonies • Proboscis is sheild-like and secretes the tube • Found mostly in deep oceans of the Southern hemisphere • Use cilia on arms/tentacles to filter and transport food to mouth Phylum Chordata Subphylum Subphylum Subphylum Urochordata Cephalochordata Vertebrata tunicates lancets Agnathans Fish Sharks tetrapods Characteristics of Chordates Possible evolution of 1st fish 1st fish lancelet Proto-vertebrate Tunicate larvae Adult tunicate Early Chordate ancestor may have given rise to 1st vertebrate Pikaia Burgess Shale Fauna Cambrian 540-500 mya General Features Shared by Chordates: 1. Eukaryote 2. Multicellular 3. Bilateral- deuterstomes 4. Heterotrophic Phylum Chordata Subphylum Urochordata - Tunicates Class Ascidiacea - Sea Squirts Solitary e.g. Styela montereyensis Colonial - in groups but with own tunic Compound Colonial - colonial with shared tunic Class Thaliacea - Salps (free swimming), planktonic Class Larvacea - Gelatinous house, planktonic Subphylum Urochordata tunicate Subphylum Urochordata = tunicate Tunicate - also called 'sea squirt' • notochord is confined to the tail • notochord is lost during metamorphosis into sessile adult • possess pharyngeal slits • Repro- sexual (hermaphroditic) & asexual (budding) Tunicate Adult Anatomy Tunicates: Free swimming larva: • notochord present only in free-swimming larvum • notochord does not extend into head • larvum is free-swimming but non-feeding • adult is sessile filter feeder Settled larva: • Settle after brief free-swimming larvum existence. • Attaches at anterior end. • Metamorphosis begins. • Body turns 1800. • Tail, notochord, dorsal nerve cord, disappear. Class Larvacea - planktonic Oikopleura Class Larvacea - Gelatinous house, planktonic Jelly-like house Oikopleura Marine snow Class Thaliacea - Salps (free swimming), planktonic Pyrosoma- bioluminescent Colonial salp Class Ascidiacea - Sea Squirts Subphylum Cephalochordata lancet • Strictly marine • Live buried in sand with head sticking out • Filter feeders Lancet Anatomy Vertebrate Higher Classification Superclass Agnatha - without jaws Class Myxini – hagfishes Class Cephalaspidomorphi – lampreys Superclass Gnathostomata – with jaws Class Chondrichthyes – sharks, rays, chimaeras Class Actinopterygii – ray-finned fishes Class Sarcopterygii – lobe-fin fishes Class Amphibia – frogs, salamanders Class Reptilia – snakes, lizards, crocodiles Class Aves - birds Class Mammalia - mammals Agnatha (jawless fishes) • Lack: paired fins, scales, & well developed vertebrae • Hagfish (slime eels) – Mucus for protection – Feed on decaying flesh • Lampreys – Parasitic – Anadromous • Marine adults, breed in freshwater Subphylum Class Chondrichthyes Vertebrata Sharks, skates, rays, chimera Chondrichthyes (cartilagenous fishes) • Heterocercal tail • Two dorsal fins • Paired pectorals • 5-7 gill slits • ureoosmotic Osteichthyes (bony fishes) • Swim bladder • Operculum (gill cover) • Homocercal tail • Scales of bony origin – Smooth cycloid – Spiny ctenoid Swim Dorsal fin Adipose fin Caudal Spinal cord bladder (characteristic of trout) fin Brain Nostril Cut edge Anal fin of operculum Liver Lateral Gills Anus line Heart Gonad Stomach Urinary Kidney Pelvic bladder Intestine fin Class Amphibia Characteristics • Cold blooded • Returns to water to breed • Metamorphosis • Some toxic • Estivation-dry and hot • Hibernation- cold 3,500 species Class Amphibia salamander newt Mudpuppy (salamander) Poison arrow frog Rana cancrivora Coqui Class Reptilia Characteristics • Cold blooded • Have scales • Amniotic egg • Dry skin • 3 chambered heart (except crocks) 6,500 species Class Reptilia Marine iguana Saltwater crocodile Marine turtle Sea snake Class Aves Characteristics • Warm blooded • Feathers and wings • Hollow bones • Horny bill • Lungs have air sacks • Hard egg shell Class Aves Class Mammalia Characteristics • Warm blooded • Have fur or hair • Suckle young • 3 middle ear bones Class Mammalia Subclasses • Protheria- echidna & platypus • Metatheria- marsupial • Eutheria- true mammals .
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