Phylum Chordata the chordates

Phylum Chordata chordates Primary characters include: Notochord

Phylum Chordata Primary Characters pharyngeal gill slits dorsal nerve cord ventral heart post anal tail

Phylum Chordata Secondary Characters tailed larvae or direct development dorsal and ventral blood vessels; closed circulatory system endoskeleton

Phylum Chordata Includes two groups: Protochordata or Acraniata – those without a cranium Craniata – those with a cranium

Phylum Chordata Group Protochordata (=Acraniata) (the first chordates) Includes two subphyla: Urochordata – tunicates or sea squirts Cephalochordata- lancelets

Subphylum Urochordata (tunicates or sea squirts) about 2000 species all marine, free-living or sessile, solitary or colonial adult has no coelom; no segmentation, no bones have a test or tunic; made of cellulose

Subphylum Urochordata (tunicates or sea squirts) dorsal atrium, chamber used for filter feeding there is a heart, with colorless blood respiration is probably function of pharynx

Subphylum Urochordata (tunicates or sea squirts) notochord is restricted to tail, and is found only in larvae (except for one class- there are 3 classes) larvae are called "tadpole larvae“

Subphylum Urochordata (tunicates or sea squirts) most species are hermaphroditic, fertilization is external some species reproduce asexually through budding

Subphylum Cephalochordata (lancelets) about 23 species all marine, free-living or sessile, solitary or colonial, live on bottom no well developed head

Subphylum Cephalochordata (lancelets) many gill slits in pharyngeal basket, act in excretion and respiration have a tail; projects behind anus muscles arranged in blocks- myotomes have a notochord made of muscle fibers

Subphylum Cephalochordata (lancelets) are microscopic suspension feeders has closed circulatory system, with colorless blood sexes are separate; fertilization is external

Phylum Chordata Group Craniata (the vertebrates) Includes one subphylum: Subphylum Vertebrata

Phylum Chordata Subphylum Vertebrata Contains a wide variety of animals that include: Class Myxini – hagfishes Class Cephalaspidomorphi – lampreys Class Chondrichthyes – sharks and rays Class Osteichthyes- bony fishes Class Amphibia – amphibians Class Reptilia – reptiles Class Aves – birds Class Mammalia - mammals

Subphylum Vertebrata Divided into: Without useable jaws Agnatha With useable jaws Gnathostomata

Subphylum Vertebrata Earliest vertebrates were jawless: Agnathans Earliest of these were Ostracoderms 500 million years ago

Subphylum Vertebrata Earliest jawed vertebrates or Gnathastomes Earliest of these were Placoderms 400 million years ago