$(1)$ Give scientific reason: Meiosis is called reductional division.
$(2)$ Give scientific reason: Mitosis is necessary for growth,development,and repair of the cell.

(N/A) $(1)$ During meiosis,the chromosome number is reduced to half in the daughter cells compared to the parent cell. Therefore,it is known as reductional division. The cells transition from a diploid $(2n)$ state to a haploid $(n)$ state.
$(2)$ The life of a living organism begins from a single-celled zygote. Cell division adds new cells to the body,which is essential for growth and development. Mitosis produces genetically identical daughter cells,which replace damaged or dead cells,thereby facilitating tissue repair and maintenance.