During embryonic development of animals, tissue layers form. this process of embryonic tissue development is called

This process of embryonic tissue development is called Gatrulation. This is a phase during the embryonic development of most animals during which the single layered blastula is reorganized into a trilaminar which is a three layered structure called the gastrula. The layers are namely; the ectoderm, mesoderm, and endoderm.  Endoderm the most internal layer forms the lining of the gut and other internal organs. 

If you get a map and put the countries a states all together it forms all one piece you can also tell because of the earth quakes

4, two dominant and two recessive