Final answer:
The splitting of a zygote into two can result in the formation of monozygotic twins. If the split happens at the two-cell stage, each twin will have its own placenta, while a split at the blastocyst stage would lead to a shared placenta and chorionic cavity.
Step-by-step explanation:
When a zygote splits into two during early development, this can lead to the formation of monozygotic twins, also known as identical twins. The timing of when the zygote splits can affect the twins' shared structures. An early split at the two-cell stage means the twins will typically have their own individual placentas. Alternatively, a later split during the blastocyst stage, where there are 70-100 cells, can result in the twins sharing a placenta and a chorionic cavity.
Detailed understanding of these developmental stages begins with the process of cleavage, where the zygote divides into multiple cells to form a blastula, which is a hollow ball of cells surrounding a fluid-filled cavity. Subsequently, the blastula transitions into a more advanced stage known as the blastocyst for mammals, which features a distinct inner cell mass critical for further embryonic development.