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Phylum Chordata General Characteristics and Phylogeny Basic Chordate Characters • • • • • notochord dorsal hollow nerve cord postanal tail segmental muscles pharyngeal slits and bars (ventral heart) A Simple Chordate (Amphioxus) compare Hickman p. 273-274 Chordate Locomotion • Notochord stiffens the long body axis – pressurized cartilage material bound in fibrous sheath • segmental muscles (myomeres) act on notochord to produce undulating motion • dorsal nerve cord branches to each set of muscles to coordinate swimming motion • postanal tail and caudal fin add power Chordate Feeding • Basic pattern is filter-feeding – Water passing through pharyngeal slits is strained by bars between them. – Cilia move food particles trapped in mucus on pharyngeal bars along ventral and dorsal tracks to stomach – Pharyngeal slits and bars are metameric Chordate Examples • • • • • • sea squirts, lancelets, lamprey eels sharks, rays, trout, bass, tuna lungfish, frogs, salamanders snakes, lizards turtles, crocodiles, dinosaurs, birds mice, elephants, whales, dogs, people Chordate Subphyla Urochordata, Cephalochordata, and Introduction to Craniata, Snot otter stories Common Names • Urochordata – sea squirts, salps, larvaceans • Cephalochordata – lancelets • Craniata – hagfishes, lampreys, fishes, etc. subphylum Urochordata “notochord in the tail” • only the larvae have full chordate characters – adults greatly modified – pharynx with slits is main character • adults are sessile or planktonic filterfeeders Urochordata Tadpole Larva Hickman Fig. 14-6 Sea Squirt Metamorphosis Hickman Fig. 14-6 myomeres Sea Squirt Anatomy (adult) Hickman Fig. 14-5 subphylum Cephalochordata “notochord in the head” • notochord goes farther forward • similar to ancestor of craniates – and fossils from Burgess Shale • benthic suspension feeders • few species, but sometimes abundant Cephalochordata Anatomy gonads Hickman Fig. 14-8 lancelet, or amphioxus Craniata • phylum Chordata • subphylum Craniata – hagfishes (class name not required) • between subphylum and class - Vertebrata – lampreys (class name not required) – other fishes and tetrapods Jawless Craniates Hickman Fig. 15-3 hagfish lamprey eels, on carp Chondrichthyes Examples black-tip reef shark manta ray blue-spotted sting ray Shark Advances over Lampreys • jaws – from pharyngeal arches • bony skin plates – evolved to fish scales and teeth • pectoral and pelvic arches and fins Bony fishes • swim bladder – enabling bony skeleton, variable body forms • operculum – to force water over gills • fin skeletal support – for increased maneuverability • terminal, complex mouth External Anatomy operculum lateral line terminal mouth pectoral fin pelvic fin homocercal tail Internal Anatomy Hickman Fig. 15-13 Amphibians • “living a double life” Have aquatic and terrestrial adaptations • Eggs – fertilized in water, no shell, covered with gelatin • Aquatic larva – Tail, lateral line, gills, no legs Salamanders Tail! walking is awkward; legs out on sides of body Frogs and Toads Tail lost! ribs and neck reduced, hind legs enlarged • communicate with sound Reptiles Turtles, Snakes, Lizards, and Crocodiles nostril pit organ hollow fang poison gland glottis Reptilian adaptations • Keratin covered scales “waterproofed” • Eggs with shells that retain water – Amniotic egg • Ectothermic - do not use metabolism to alter body temperature Amniontic egg Has 4 membranes • amnion • allantoi s • yolk sac • chorion Reptile groups • • • • Lizards Turtles Crocodiles and alligators Snakes Examples of Lizards Komodo dragon iguana Examples of Snakes compare Campbell Fig. 18.20 garter snake coral snake olive sea snake timber rattlesnake Crocodilia American crocodile not an alligator: narrow snout, large lower tooth exposed with mouth closed Turtles freshwater carapace terrestrial marine plastron Birds • Amniotic eggs, scales on legs, keratin • Feathers • Reduced skeleton and large muscles for flying • Special lungs and circulatory system • Endothermic – make their own heat Mammals Basic Features of the Class Mammal Adaptations • endothermy, hair, sweat and scent glands • varying teeth (“heterodont”), epiglottis • improved olfaction, larger nasal cavity • 4-chambered heart, diaphragm • more coordination, acute senses, and learning ability Oviparous Mammals • 3 species in one order Monotremata – all live in Australia or New Guinea • lay eggs, but have hair and nurse young Campbell Fig. 18.22 (a) duck-billed platypus mother, nursing Marsupial Mammals • fetuses do not fully implant in the simpler uterus • adult females have a belly pouch (marsupium) – newborns stay inside, attached to nipple, for months Marsupial Mammals Campbell Fig. 18.22B South American tree opossum North American opossum Australian kangaroo Placental Mammals • true placenta formed by fetus and mother • Joins the embryo to the mother within the mother’s uterus • Embryo is nurtured by blood from the mother • 95% of all mammals Placental mammals
