Urochordata

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  • 3. incomplete gut - blind (has a mouth and no anus) and sac-like, often with incomplete branchings, mouth for both ingestion and egestion
  • Dugesia (Planarian): common freshwater turbellarian
  • Urochordata

    1. 1. CLASSIFICATIONKingdom: Animalia UROCHORDATA Phylum: Chordata Subphylum: Urochordata (Tunicates) Class: Ascidiacea (Sea Squirts) Anatomy of the Sea Squirt Larvacea (Larvaceans) Thaliacea (Thaliaceans)
    2. 2. GENERAL CHARACTERISTICS- Protochordates • Morphological features: notochord, dorsal hollow central nervous system, pharynx with paired pouches; muscular, post-anal tail - Group of marine chordates in which the notochord is confined to the locomotor tail of the larval stage
    3. 3. GENERAL CHARACTERISTICS- Also known as Tunicates- Enclosed in a delicate, nonliving, and sometimes beautifully colored transparent tunic- Filter-feeders.
    4. 4. CLASS ASCIDIACEA → largest class of urochordates → free-swimming larval stage → sessile as adults, either solitary or colonial
    5. 5. LARVAL STAGE - Body consists of trunk containing the immature viscera and a muscular notochord-supported tail. - The nervous system consists of a dorsal hollow nerve cord, several ganglia and nerves - Respiratory water enters the atrium chamber which is then ejected through the atriopore. - At metamorphosis, the notochord is resorbed and becomes a source of nutrients and rearrangement of the viscera takes place.
    6. 6. METAMORPHOSIS
    7. 7. ADULT- Incoming water current becomestrapped in the mucus, then the ciliaand esophageal papillae sweep themucus and entrap food particles intothe stomach.- Respiratory water passes over thegills and into the atrium, a fluid-filledcollecting chamber surrounding thepharynx. Gas exchange occurs aswater circulates with the help of theatrial muscles.- One blood vessel from the heartruns anteriorly under the endostyle,and another runs posteriorly to thedigestive organs and gonads.- Gametes may be shed through theexcurrent siphon for externalfertilization or eggs are retained forfertilization and early development.
    8. 8. GARSTRANG’S HYPOTHESIS
    9. 9. UROCHORDATA Anatomy of the Sea Squirt

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