BIOL 371 Lecture Notes - Lecture 7: Gastrulation, Lophophore, Protostome
9 May 2018
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▪ Enterocoelous coelom
• Endodermal tissue layer starts to differentiate into mesodermal
cells
• Bud off of the endodermal layer, and end up with a hollow cavity
▪ Blastopore forms the anus
• Deuter stoma
• Second opening of the mouth
• Anus forms first
o Protostome vs deuterostome in summary
▪ Protostome
• Mouth first formed
• Top on crack of the bottom
• Mesodermal cells split open to form a hollow ball
• Spiral cleavage
• Schizocoelous coelom
• Blastopore forms the mouth
• Determinate cleavage
• Ventral solid nerve cord that surrounds the digestive tract
anteriorly
▪ Deuterosome
• Top on bottom directly endodermal differently to mesodermal
• Hollow cavity
• Deuterostome
• Taking away a cell is not fatal
• Radial cleavage
• Enerocoelus coelom
• Blastopore forms the anus
• Indeterminate cleavage
• Dorsal hollow nerve cord and brain does not surround the
digestive tract
o Protostomes are further divided into
▪ Lophotrochozoans
• Some have a trocophore larva
• Some have a lophophore feeding structure
• Many do not have either
o Use molecular data to classify these
▪ Ecdysozoans
• External cuticle that is shed to grow
o Ecdysis
o Exoskeleton
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