CBSE Class 10 Answered

This is because a zygote is totipotent and has the capacity to differentiate into all the different cell types of the body. A cell that is able to differentiate into all cell types is known as totipotent.  In mammals, only the zygote and the products of the first few cell divisions (cleavage) are totipotent.

(Cellular differentiation is an embryological process by which an unspecialized cell becomes specialized into one of the many cell types that make up the body.)