Question

At which developmental stage should one be able to first distinguish the formation of tissue layers?

a. fertilization

b. gastrulation

c. metamorphosis

d. cleavage

Answer 1

B.) Gastrulation -

* During gastrulation, movement of cells result in a collective reorganization of developing embryo from a simple spherical ball of cells( blastula) into a multi-layered organism - Endoderm, mesoderm, Ectoderm.

*  Endoderm, most internal germ layer, forms the lining of the gut and other internal organs.

*  Ectoderm, the most exterior germ layer, forms nervous system, skin .

* Mesoderm, the the middle germ layer, forms skeletal system,circulatory system, muscles.

* Gastrulation involves changes in cell motility, cell shape, and cell adhesion.

*  In Drosophila, gastrulation is achieved through changes in cell shape , that change tissue curvature.