Zygote to the Bastula Stage

• Zygote= a cell that is a result from fertilization.
• Zygotes undergo mitotic cell divisions, or mitosis, to become an embryo.
• The blastula= an early stage of embryonic development in animals. It is also called the blastosphere.
• Cleavage= the division of cells in the early embryo. The zygotes go through rapid cell cycles with no significant growth and produces many cells the same size as the original zygote.
• End of cleavage is known as midblastula transition
• After cleavage has produced over 100 cells the embryo is called a blastula.

http://en.wikipedia.org/wiki/Blastula

https://en.wikipedia.org/wiki/Cleavage_(embryo)