Vertebrata is a subphylum under phylum: Chordata, which is the same level as phylum: Mollusca, phylum: Arthropoda. Other subphyla same level as phylum: Chordata are subphylum: Turnicata, subphylum: Cephalochordata.
Porifera is porous, which is made out of porocytes. The water is transfered by flagellum of collar cells out to the osculum. The outer surface is covered by epidermal cells and mesohyl fills the space between the inner cellular layer. Amoebocytes wander in the mesopyl. There are three class of sponges: 1. Calcispongiae, which has CaCO spicules. 2. Hexactinellida(glass sponges), which has silicon spicules. 3. Demospongia, which has variable skeleton. Sponge is made out of spongin of the Demospongia. Most sponges produce both eggs and sperm( hermaphroditic). Cnidaria has cnidocytes which stings: the nematocysts release a thread when triggered(cnidocil) is stimulated by touch or chemicals and inject protein toxin. The cnidocytes are disposable. The mouth of Cnidaria is diretly connected to gastrovascular cavity. Cnidarians form layered gastrovascular cavity: epidermis, and gastrodermis, separated by gelatin-like mesoglea. Cnidarians are the first to have nerve nets, which is not centralized. Planarians(cl. Tubellaria) have protonephridia whose branches spread all over its body, which ends in flame cell. The flame cell has cilia that pumps the water. Tapeworms(cl. Cestoda) has the head(scolex) and segments called proglottids which produces both gametes. The sucker of Tapeworms directly absorbs nutrients. Tapeworms have no digestive tract, nor sensory organs. Nematoda can be pathogenic: Ascaris causes peritonitis. Hook worm, trichina worm, pinworm and filaria resides in intestine. The cysts of trichina worm calcifies and damages the muscle. Rotifera, the wheel animals maintain constant number of cells. Rotifera has mastrax to grind food.
Amphioxus is a protosome.
Turnicates has tunic which contain cellulose.
Hirudinea secrtes hirudin which is an antigoagulant.
cl. Amphibian proliferated in Carboniferous until Permian.
Vascularized bone is an evidence of homeotherms such as in dinasours.
