Final answer:
Cell division occurs for several reasons: to replace old cells, to repair damaged tissue, as an organism grows, and before it gets too big.
Step-by-step explanation:
Cell division occurs for several reasons:
To replace old cells: Over time, cells wear out and need to be replaced. For example, new blood and skin cells are constantly being produced.
To repair damaged tissue: When an injury occurs, cells divide to produce new cells that can heal the damaged area. For instance, if you cut your finger, some of your existing skin cells will divide and produce new cells to repair the wound.
As an organism grows: During development, a single cell divides repeatedly to produce an entire organism. For example, an embryo forms from a one-celled zygote and keeps dividing to create more cells and eventually develop into a complex, multicellular human.
Before it gets too big: Some cells divide to control their size. If a cell grows too large, it may not be able to efficiently carry out its functions. Dividing into smaller cells can help maintain optimal cell size and function.