9. What is gastrulation? How
during gastrulation are the
first two germ layers formed?
What are these germ layers?

Gap-fill exercise

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Gastrulation is the process
which a portion of blastula wall
under goes inside the
blastocele, forming tube called
archenteron (primitive ). The
cells of the side of the tube
the endoderm (germ layer) the cells
of the side form the ectoderm
( germ layer). It is beginning
of the tissue in embryonic
development.