Question

what happens after the formation of blastula and when the term layer is formed​

Answer 1

Explanation:

The cells of the blastula form an epithelial (covering) layer, called the blastoderm, enclosing a fluid-filled cavity, the blastocoel. After the blastula develops, it undergoes transition to the gastrula (q.v.), a process called gastrulation. In organisms such as mammals, the earlier morula (q.v.), a berrylike cluster of cells, develops into a somewhat different form of blastula, the blastocyst (q.v.).

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Answer 2

The blastula eventually organizes itself into two layers :-

1) the inner cell mass (which will become the embryo) and

2) the outer layer or trophoblast (which will become the placenta ) and the structure is now called a blastocyst .