Unit 1 - Vertebrate Development - Review
Comparison of Frog and Bird Embryology
Cleavage Fertilized egg (zygote) rapidly divides to Zygote rapidly divides, but cleavage is limited
form a morula (solid ball of cells). to a disk due to the large yolk.
Blastula Formation Cells form a blastula, with the hollow space Hypoblast forms on top of the yolk, with the
inside called the blastocoel. epiblast on top. Space between hypoblast
and epiblast is the blastocoel.
Gastrulation Cells from outer surface migrate through Cells from the outer surface migrate through
the blastopore, forming the three the primitive streak, forming the three
embryonic layers. embryonic layers. Hensen’s node then moves
posteriorly to close the primitive streak.
Neurulation Mesoderm further differentiates and the neural tube and notochord appear.
Coelom formed from hypomere mesoderm; dorsal and ventral mesentery formed.
All vertebrates: Coelom divided by transverse septum into pericardial and
Mammals: Coelomic fold furthe