Practice question

Subphylum Urochordata, synonymous with Tunicata, includes marine filter feeders like Herdmania, Ciona, Salpa, Doliolum and Pyrosoma encased in secreted tunic composed of tunicin resembling cellulose. Adults are sessile, sac-like with incurrent and excurrent siphons, lacking notochord, dorsal nerve cord and segmented muscles due to retrogressive metamorphosis where tail resorbed. Free-swimming tadpole larva retains chordate features for dispersal. Cephalochordata contains Branchiostoma amphioxus, Agnatha contains lampreys, Chondrichthyes sharks and bony fishes. Tunicate classification emphasizes loss of chordate traits in adult demonstrating developmental plasticity within protochordates.