Notochord –Supportive Longitudinal Rod (becomes a backbone in most Vertebrates) Dorsal Hollow Nerve Cord –Creasted from ectoderm infolding Pharyngeal Gill Slits –Pouches or grooves along the pharynx Post-Anal Tail Phylum: Chordata
Chordata Subphylum: Urochordata (Tunicates) –Simplest & Most Ancient Chordates –Adult is a Sessile filter-feeder METAMORPHOSIS –Larva is a free-swimming “tadpole” ADULT LARVA
Subphylum Cephalochordata (Lancelets) –Both Larva & Adult are “tadpole-like” –Neotony – retention of larval characteristics in the adult – “juvenile” characteristics are carried into adulthood. (Metamorphosis becomes less pronounced) Chordata
Subphylum Vertebrata (Vertebrates) Chordata Notochord is composed of segments (sometimes bony “vertebrae”), often enclosing the dorsal hollow nerve cord. “Craniates” = advanced cephalization (formation of a head region – a cranium).
CLASS Cephalaspidomorphi (Lampreys) –Hollow cartilage endoskeleton (with segmented projections) surrounding a persistent notochord. –Jawless (Agnathostomes) –Mostly parasitic Chordata
CLASS Placodermi (Placoderms) –1 st Jawed vertebrates (Gnathostomes) –Extinct –Armored plates. –Likely a cartilage endoskeleton Chordata
CLASS Chondrichthyes (Sharks, Rays) –Cartilaginous Fish – Cartilage endoskeleton. –Well-developed jaws. –Continual swimmers (density > water) –Placoid (tooth-like) scales (actual teeth too) –Oviparous, Ovoviviparous, or Viviparous Chordata
CLASS Actinopterygii (Ray-finned Fish) –(Osteichthyes) - bony fish (calcium phosphate- enriched endoskeleton = ossified endoskeleton) –Highly maneuverable (ray-fins) –Swim Bladder (buoyancy control) –Respiratory gills supported by a bony flap. Chordata
CLASS Sarcopterygii (Lobe-finned fish) –Large muscular pegs within pectoral & pelvic fins (pulled fish through mud flats). CLASS Dipnoi (Lung fish) –Gulp air into rudimentary lung-like sacs. Chordata Coelacanth (Class Actinistia) Australian Lungfish
Chordata Origin of Tetrapods -- 4 limbed organisms Bones & muscles modified for land motility.
CLASS Amphibia (Salamanders, frogs) –Metamorphosis (“two lives”). Aquatic herbivorous larva (tadpole) with gills. Semi-aquatic or aquatic carnivorous adult, sometimes with lungs. –Skin often functions in gas exchange. –Water required to complete the life cycle. Chordata
Origin of Amniotes – an amniotic egg (surrounded by layers of tissue) –allows for exclusive occupation of land.
CLASS Reptilia (dinosaurs, lizards, snakes, turtles, birds) –Skin with Keratinized scales. –Lungs. –Most are Ectothermic (cold-blooded). Chordata