Final answer:
Mitosis, specifically cleavage divisions, is responsible for the growth and development of a zygote into a multicellular organism, resulting in a morula and subsequently a blastocyst.
Step-by-step explanation:
After fertilization, the type of cellular division responsible for the growth and development of the resulting zygote is called mitosis, which includes a series of divisions known as cleavage. The zygote first undergoes cleavage as it passes through the fallopian tube, forming two cells, then four, eight, and so on, eventually becoming a solid ball of cells called a morula. As the cleavage continues, the cells increase in number but not in size; they remain confined within the zona pellucida, ensuring the overall conceptus does not grow in volume. Following further divisions, a fluid-filled cavity develops, transforming the morula into a blastocyst, which then implants into the uterine wall, beginning the next stage of embryonic development.