Final answer:
The basis of all reproduction, growth, and repair in multicellular organisms is the ability of cells to undergo cell division, starting from a single cell and expanding into a complex organism.
Step-by-step explanation:
The ability of cells to duplicate themselves through cell division is fundamental for the processes of reproduction, growth, and repair in multicellular organisms. Starting from a single fertilized egg or zygote, a multicellular organism develops through numerous cell divisions. As the organism grows, the continuous production of new cells is crucial for tissue repair and regeneration, such as the constant replenishing of blood and skin cells. In single-celled organisms, cell division serves as the method for reproduction. It's essential to understand that the process of cell division must be tightly regulated, as disruptions can lead to severe and sometimes fatal consequences.