Why is DNA replication necessary?
Reproduction of cells and organism are dependent on DNA replication.
The information stored in the DNA is essential for life. If a cell dies the body must replace that cell. The only way to replace the cells is to first copy the information that the cell contained. There is a complex system of proteins and enzymes that unravel the DNA double helix so that the DNA can be copied.
If a single cell dies it can be replaced through mitosis. The two daughter cells are identical to the original cell whose DNA was copied. This system works well with single cell and simple organisms.
More complex organisms use meiosis to produce gametes (egg or sperm cells) for sexual reproduction. Meiosis also begins with DNA replication. Each gamete has half the amount of DNA as the parent cell. When a sperm fertilizes the egg, a new cell containing a complete copy of DNA forms for that species forms, called a zygote.
Without the copying of the DNA life would not continue as existing organisms would not be able to reproduce and replace themselves.
Life is dependent on the information stored on the DNA. Without replication of the DNA the information would not be passed on and life would cease to exist.
This video provides an animated tutorial about DNA replication.