BI 173 - Chapter 26 - Chordates.

    Bilateral Symmetry, commonly w/ Cephalization.

    Notochord. Two functions (either / or)

    Dorsal Nerve Cord - Single, Tubular.

    Pharyngeal Pouches - Gill Slits.

    Tail is Postanal, internally-supported.

    Coelom.

    1-Way Digestive system, "complete."

    Segmentation - in muscle structure, nervous system.

    Endoskeleton, usually.

    Closed Circulatory System w/ ventral heart.

    Digestive System - One-Way tube, non-segmented.

    Sexual, mostly dioecious species.

    Probably share ancestor w/ echinoderms.

    Tunicates - Urochordata.

        Sea Squirts. Filter feeders.

        Swimming Larvae, sessile adults.

    Lancelets - Cephalochordata.

Vertebrate Chordates:

    Additional characteristics:

         Epidermis & Dermis. Many covering adaptations.

        Notochord pretty much replaced w/ vertebral column.

        Skull generally present.

        Paired fins or limbs usually present.

        Complex muscle systems.

        Digestive System w/ accessory glands.

        2-4 Chambered Heart. RBCs & WBCs.

        Paired Kidneys.

         Complex Brains w/ Cranial Nerves & Autonomic NS.

        Endocrine system.

    Ancestry:

        Lancelet- like Protochordates.

            Cephalization, cranial protection of brain.

            Muscular mouth / throat w/ efficient gill circulation.

                Supports --> Jaws, etc.

            Materials: Teeth --> Jaws --> Bone.

        Primitive Fish. Armored & Nonarmored.

Michael McDarby,
        Based Upon Hickman-Roberts-Larson Biology of Animals,
            1998, WCB McGraw-Hill.
        Internet Version Uploaded 2001.