Explain the biological significance of mitosis

Mitosis is important for a number of reasons. It's a form of reproduction for some organisms that reproduce asexually, it's needed for growth and development, and also for the repair and replacement of cells. If we didn't do mitosis dead cells wouldn't be replaced, and that would cause some massive problems. For example, if we weren't capable of doing mitosis and you cut your hand, the cut wouldn't heal up because the cells wouldn't be getting replaced.

It is important for asexual cellular reproduction so that an organism can heal a wound, grow larger systems such as organs, and replace sick or dead cells.