After about the eight-cell stage within the zygote, cells start to meaning that they take different forms and reproduce at various rates depending on where they are located

After about the eight cell stage within the zygote, cells start to DIFFERENTIATE. Differentiation is defined as the process by which cells becomes specialized during developmental process. Cellular differentiation occur so that the cell can become specialize for a specific purpose and function which they will maintain all through the life span of the animal, they can be repaired and changed but their functions remain the same.