Final answer:
Two sea urchin larvae can develop if the two cells produced by the first cell division of the zygote are separated, which then allows each cell to follow its own developmental trajectory through cleavage and forming a blastula.
Step-by-step explanation:
The development of multi-cellular organisms, like sea urchins, begins from a single-celled zygote. This zygote undergoes a process known as cleavage, which is a series of rapid cell divisions. After the first cell division, the zygote has divided to form two cells. If these two cells are separated at this early stage, each one has the potential to develop into a separate sea urchin larvae.
Continuing with the cleavage process, after four rounds of cell division, there will be 16 cells, forming a structure known as a blastula. The blastula is typically a spherical layer of cells surrounding a cavity. This process of early development in sea urchins and other multi-cellular organisms is vital for understanding embryogenesis and is commonly studied in developmental biology. In sea urchins specifically, two separate larvae can develop if the two cells produced after the very first cell division are separated, allowing each cell to individually continue through cleavage, blastula formation, and subsequent development stages.