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Phylum Hemichordata | General characters of Hemichordates | Fsc by irtisamsbiology

#PhylumHemichordata #hemichordata #fscbiology #irtisamsbiology Hemichordates are distinguished by a tripartite (threefold) division of the body. At the forward end of the body is a preoral lobe, behind this is a collar, and last comes a trunk. The name "hemichordate" means "half chordate," and hemichordates share some (but not all) of the typical chordate characteristics. There are branchial openings, or "gill slits," that open into the pharynx; there is a rudimentary structure in the collar region, the stomochord, that is similar to a notochord; and there is a dorsal nerve cord, in addition to a smaller ventral nerve cord. However, hemichordates are not classified as true chordates, although they are quite closely related. Some DNA-based studies of evolution suggest that hemichordates are actually closer to echinoderms than to true chordates. This is supported by the fact that the larvae of at least some hemichordates look very much like those of some echinoderms.