DNA determines the body design of an individual. The DNA that gets transferred from parents to offspring makes them look similar. DNA copying is important for reproduction. Additional copies of DNA are made during replication necessary for the new cells formed after cell division. Moreover, some minor alterations during DNA replication are responsible for bringing variations in the long run.
DNA copying refers to the replication of DNA at the time of cell division. It is important to transfer genes of the parent(s) to the next species of the same kind. The continuity of the existence of species is based on this factor. This process becomes specifically important in the organisms that reproduce asexually. In such organisms, only one parent is involved, and there is no other source of variation in the DNA of the progeny from the parent.
Example: If a species can survive in suitable water at some temperature. But due to climatic changes, there would be a change in water temperature, so the species may die and become extinct. But this does not happen in nature as there is always some change in DNA replication and some identical species, but they are similar. Due to this little variation in their DNA, some individuals of this species of bacteria will be capable of surviving in warmer water, thereby ensuring the continuity of species. This is how variations incorporated in DNA during replication are important.