BIOL2712 Study Guide - Final Guide: Neural Crest, Pharyngeal Groove, Thyroid
25 Jun 2018
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Hemichordates to Chordates
Hemichordates
Pharyngeal gill slits (or pores), ciliated
Ventral and dorsal nerve chords
oNot homologous to notochord
Bilateral Deuterostomia
Trimeric
oProtosome
oMesosome
oMetasome
Complete gut
Tornaria larvae
oEchinoderm larvae
Heart
Glomerulus
Marine
Enteropneusta
oAcorn worms
oSolitary
o2m
oBurrowing
Psterobranchia
oSea angels
oColonial
o1cm
oTube dwelling
oCollar bear arms with tentacles
oGill slits reduced
Chordates
5 diagnostic features
Bilateral symmetry
Segmented body and muscles (not of coelom)
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1 Dorsal nerve chord, anterior end
enlarged to brain
2 Notochord (present at some life
stage)
Ventral heart
3 Pharyngeal slits/pouches
4 Endostlye (in pharynx)
5 Postanal tail
Characteristics of Chordates
Notochord
oCartilarginous rod enclosed
by sheeth
Semi-rigid, flexible ‘skeletal rod’
Lies underneath nerve cord, supporting it
First part of skeleton to appear in embryo
Axis for muscle attachment
Extends full body length, but:
oPresent through life only in Agnatha
In Gnathostomata in early development
Cartilaginous or bony endoskeleton
Endostyle
Urochordates (tunicates)
Notochord characterizes the larval swimming stage
oDoes not extend into the head
Restricted nervous system
Tough surrounding, contains cellulose
Pharynx
oBranchial sac
Endostyle
oSecretes mucus
oTraps particles
Heart
oBlood flow changes directions between beats
Gonads (ovary and testes)
oHermaphrodites
oCross-fertilisation
Stolons
oattachment
Ascidiacea (sea squirts)
oSolitary or colonial
Larvacea/Appendicularia
oPlanktonic
oBioluminescence
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Document Summary
Ventral and dorsal nerve chords: not homologous to notochord. Psterobranchia: sea angels, colonial, 1cm, tube dwelling, collar bear arms with tentacles, gill slits reduced. 1 dorsal nerve chord, anterior end enlarged to brain. Notochord: cartilarginous rod enclosed by sheeth. First part of skeleton to appear in embryo. Extends full body length, but: present through life only in agnatha. Notochord characterizes the larval swimming stage: does not extend into the head. Heart: blood flow changes directions between beats. Gonads (ovary and testes: hermaphrodites, cross-fertilisation. Branchiostoma: branchia = gills, stoma = mouth. Closed circulatory system (no heart and no gills) Tentacles: used for feeding, suspension feeding (gill slits) Notochord extends to the extreme tip of the head: in both young and adults. Notochord becomes surrounded by skeletal vertebrate: during embryonic development. Tube, but hollow centre may be filled during growth. In craniata (vertebrata: passes through neural crests of vertebrae, brain encased by cranium.
