Here's why:

* Replication creates copies: DNA replication is the process where the entire genome is duplicated. This is essential for both cell division processes.

* Mitosis: Mitosis creates two identical daughter cells from a single parent cell. Each daughter cell needs a complete set of chromosomes, which is why replication must occur beforehand.

* Meiosis: Meiosis creates four haploid gametes (sex cells) from a single diploid cell. Again, each gamete requires a complete set of chromosomes, making replication a necessary precursor.

In summary: Replication is a crucial step that happens before both mitosis and meiosis, ensuring that each resulting cell has a complete copy of the organism's genetic material.