Both Blastula and Gastrula represent different stages of embryo formation during the process of embryogenesis. This process has four developmental stages, the fertilization, cleavage, gastrulation, and organogenesis. The Blastula is formed immediately after fertilization has occurred through the fusion of haploid cell of the female and the male gamete. The cleavage that is formed after fertilization is what is known as the Blastula. After this stage, the next developmental stage is what leads to Gastrula through the process known as gastrulation.
The rapid mitotic division of the zygote is what leads to Blastula, while the slow mitotic division of Blastula is what forms the Gastrula. Also, during blastulation, there is no movement of the cells, whereas there is an increase in the number of cells, and the cells move during the formation of Gastrula. Another thing is that Blastula is formed when the embryo has not fully matured, while gastrulation leads to the formation of the matured embryo.
There are many stages of an animal's embryonic development. Blastula and Gastula are two of those stages. The Blastula is the early stage of development. When this occurs, the embryo is a ball of hollow cells. The Gastula stage follows Blastula. It includes the three-layer of cells. Blastula has 128 cells.
While no number is known, Gastula has over 123 cells, which are more cells than Blastula. Another difference between them is that Blastula will have a zona pellucida, while Gastula does not. Blastula will also contain undifferentiated cells, while Gastula has differentiated cells. They both form during different processes. Blastula forms during blastulation, while Gastula forms during gastrulation.