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Phylum Chordates

Phylum Chordates. Characteristics. Characteristics similar to other phylum discussed: Bilateral symmetry Triploblastic Well-developed coelom Metameric - Segmented body “tube within a tube” arrangement Cephalization. Characteristics. Deuterostome Radial clevage Anus forms first

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Phylum Chordates

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  1. Phylum Chordates

  2. Characteristics • Characteristics similar to other phylum discussed: • Bilateral symmetry • Triploblastic • Well-developed coelom • Metameric- Segmented body • “tube within a tube” arrangement • Cephalization

  3. Characteristics • Deuterostome • Radial clevage • Anus forms first • Primitively Enterocoelous • Early chordates were known to be enterocoelous, however, due to the large yolk of modern species, most vertebrates are schizocoelus

  4. Characteristics • 5 distinctive characteristics that set chordates apart from all other phyla: • Notocord • Dorsal tubular nerve cord • Pharyngeal pouches or slits • Endostyle • Postanal tail

  5. 1. Notocord • All members of this phylum contain a notochord (noton, back + chorda, cord) • Can be restricted to early development or may be present throughout life • Rod like, semi rigid body of cells enclosed by a fibrous sheath, which extends the length of the body just ventral to the central nervous system. • Primary purpose is to stiffen the body, providing skeletal scaffolding for the attachment of swimming muscles

  6. 2. Dorsal Tubular Nerve Cord • Solid, single nerve cord is dorsal to the alimentary canal and is a tube • Hollow center • Anterior end becomes enlarged to form the brain

  7. 3. Pharyngeal Pouches and Slits • Slit openings • Give rise to several structures: • Middle ear cavity • Tonsils • Parathyroid glands • Eustachian tube (equalizes pressure between ear and nasal canal, surrounding ear drum) • Gills

  8. 4. Endostyle or Thyroid Gland • Endostyle- secretes mucus that traps small food particles • Work together with hormone secretion

  9. 5. Postanal Tail • End of the notochord (stiffened) • Used primitively for swimming • Humans have evidence of the tail but evidently it is vestigal (the coccyx, tail bone)

  10. Divisions of the Phylum Chordata • Protochordata (Acraniata)- lack a well-developed head • Subphylum Urochordata • Tunicates • Subphylum Cephalochordata • Lancelets • Vertebrata (Craniata) – has a well-developed head • Tunicates

  11. Divisions of the Phylum Chordata • Agnatha- vertebrates lacking jaws • Hagfishes and lampreys • Gnathostomata- Vertebrates having jaws • All other vertebrates • Two forms • Pisces- jawed vertebrates with appendages • Tetrapoda- jawed vertebrates with appendages in the form of limbs • Amniota- vertebrates whose embryos develop within a fluid-filled sac • Reptiles, birds, mammals • Anamniota- vertebrates lacking this adaptation • Fishes and amphibians

  12. Phylum Chordates EVOLUTION

  13. Subphylums • There are 3 subphylum belonging to the phylum Chordata • Remember we have already discussed two: • Protochordata (lack a well-developed head) • Subphylum Urochordata (tunicates) • Subphylum Cephalochordata (lancelets)

  14. Further Divisions • Subphylum Vertebrata (have a well-developed head) • Super class Agnatha (lack Jaws) • Class Myxini (hagfish) • Class Petremyzontida (lampreys) • Super Class Gnathostomata (have jaws) • Pisces (Jaws with appendages) • Class Chondrichthyes (cartilaginous fishes) • Osteichthyes (boney fishes) • Class Actinopterygii (ray-finned fishes) • Class Sacropterygii (lobe-finned fishes) • Tetrapoda (Jaws with appendages as limbs) • Class Amphibia • Class Reptilia • Class Aves • Class Mammalia

  15. New Evolutionary Tree • Must include when the following traits emerged: • Protochordata • Vertebrata • Agnatha • Gnathostomata • Pisces • Tetrapoda • Use pg 499 in your text book as a reference • Also include the Phylum Echinodermata • Use front cover and pg 473 • Save room for Subclasses, Orders and Suborders

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