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BIO153H5 (147)
Chapter 34

Chapter 34 Notes.docx

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University of Toronto Mississauga
Christoph Richter

Chapter 34 NotesThe deuterostomes include the largestbodied and some of the most morphologically complex of all animals Range from sea stars that cling to dock pilings on the west coast of Vancouver Island to the fish that dart in and out of coral reefs in the Caribbean Sea to the wildebeests that migrate across the Serengeti Plains of East AfricaWhen humpback whale sea urchin or human just beginning to grow the gut starts developing from posterior to anteriorwith the anus forming first and the mouth second A coelom develops from out pocketings of mesoderm Four phyla of deuterostomes1Echinodermata2Hemichordata3Xenoturbellida4ChordataEchinoderms include the sea stars and sea urchinsThe hemichordates acorn worms are probably unfamiliar to youthey burrow in marine sands or muds and make their living by deposit feeding or suspension feedingA lone genus with 2 wormlike species called the Xenoturbella recognized as a distinct phylum in 2006The chordates include the vertebrates or animals with backbones plus a few invertebrate taxa The vertebrates comprise the hagfish lampreys sharks bony fishes amphibians mammals and reptiles including birdsThe echinoderms named for spikes observed in many species Echinodermata is a large and diverse phylum that is exclusively marine ndThey are the 2 most successful lineage of deuterostomesnext to vertebratesAbundantECHINODERM BODY PLANAll deuterostomes are considered bilaterians because they evolved from an ancestor that was bilaterally symmetric Echinoderm larvae also bilaterally symmetricRemarkable event early in the evolution of echinoderms the origin of fivesided radial symmetry called pentaradial symmetry in adultsIf adult echinoderms are capable of movement they tend to move equally well in all directionsHas an endoskeleton a hard structure located just inside a thin layer of epidermal tissue that provides protection and support As individual is developing cells secrete plates of calcium carbonate inside the skin Depending on the species involved the plates may remain independent and result in a flexible structure or fuse into a rigid case If plates do not fuse they are connected by an unusual tissue that can be stiff or flexibledepending on conditions Another remarkable event in echinoderm evolution was the origin of a unique morphological feature a series of branching fluidfilled tubes and chambers called the water vascular
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