The non-chordate phyla, from Porifera to Hemichordata: sponges, cnidarians, comb jellies, flatworms, roundworms, annelids, arthropods, molluscs and echinoderms.
3 lessons, about 1 h 25 min3 simulations10 problems3 practice questionsPython in every lesson
Created by StemPy LabSponges (Porifera) have a cellular level of organisation. Water enters through ostia, passes the collar cells in the spongocoel and leaves by the osculum. Cnidarians have stinging cnidoblasts, a gastro-vascular cavity with one opening, and two body forms, the polyp and the medusa, which alternate in Obelia. Comb jellies (Ctenophora) swim with eight rows of comb plates and glow by bioluminescence.
Flatworms (Platyhelminthes) are flattened, acoelomate and mostly parasitic, with hooks, suckers and flame cells; Planaria regenerates well. Roundworms (Aschelminthes) are round in section, pseudocoelomate and dioecious, with a muscular pharynx. Annelids are metamerically segmented and coelomate, with nephridia, a closed circulation and a double ventral nerve cord. Nereis has parapodia; earthworms and leeches are monoecious.
Arthropods, the largest phylum, have a chitin exoskeleton, jointed legs, an open circulation and malpighian tubules. Molluscs, the second largest, have a soft body with a head, a muscular foot, a visceral hump, a mantle and a rasping radula. Echinoderms are spiny, marine and radial as adults, with a water vascular system. Hemichordates have a proboscis, a collar and a trunk.
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