BIOL2712 Study Guide - Final Guide: Estuary, New Zealand, Crinoid
25 Jun 2018
School
Department
Course
Professor
Echinoderms & Hemichordates
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Deuterostomes
Protostomes
Cleavage mostly spiral
Endomesoderm from a particular blastomere designated 4d
Coelom forms as a split in mesodermal bands (schizocoelous)
Mouth form, at, or near blastopore: anus a new formation
Embryology mostly determinate (mosaic)
Includes:
oPlatyhelmithes
oNemertea
oAnnelida
oMollusca
oArthropods
Deuterostomes
Cleavage mostly radial
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Endomedoserm from enterocelous pouching (except chordates)
Coelom from fusion of enterocoelous pouches (except chrodates: schizocoelous)
Anus from, at, or near blastophore, mouth a new formation
Embryology indeterminate (regulative)
Includes:
oEchinodermata
oHemichordata
oChordata
Several characters not seen together in other phyla
Deuterostome = second mouth
oEnterocoelic = coelom from pouching of gut
oIndeterminate development = fate of clastomeres (cell formed by cleavage)
not determined very early
oRadial cleavage
Tripartie ogliomerism
oThree-part division
Deuterostome Origins
Ancestor probably similar to modern Hemochordates
Common deuterostome/lophophorate ancestor
oCiliated feeding device surrounding the mouth
Deuterostome taxa
oPhyla: Hemochordata, Echinodermata, Chordata
Constantly changing
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Document Summary
Coelom forms as a split in mesodermal bands (schizocoelous) Mouth form, at, or near blastopore: anus a new formation. Coelom from fusion of enterocoelous pouches (except chrodates: schizocoelous) Anus from, at, or near blastophore, mouth a new formation. Several characters not seen together in other phyla. Deuterostome = second mouth: enterocoelic = coelom from pouching of gut, indeterminate development = fate of clastomeres (cell formed by cleavage) not determined very early, radial cleavage. Common deuterostome/lophophorate ancestor: ciliated feeding device surrounding the mouth. Previously considered a subphylum of chordata: but split as show some echinoderm and chordate characteristics. Unique: rudimentary notochord (skeletal rod supporting body) evagination (protrude or turn inside out) of the mouth cavity. Echinoderm characters: diffuse net of nerve cells, early embryogenesis and larvae. Chordate characters: tubular dorsal nerve cord, gill slits in the pharynx used for filter feeding. Enteropneusts: 70 species, acorn worms, shallow bottom dwellers, burrows or under stones. Pterobranchia: 3 genera, sedentary, colonial, secrete tubes.
