DNA is the molecule that controls heredity. It is passed down from generation to generation. A species survives when its best offspring reproduce, thus passing on the most desirable genes. These genes are passed on through DNA. In organisms that produce sexually, the DNA needed to make a new organism come from a sperm and an egg. This means that the new offspring is not a perfect clone of either parent; rather, the new organism has the traits of both parents. Ideally, dominant traits are the traits that will lead to the survival of the species.
DNA replication is also important for the survival of the species because this explains how an organism is able to grow from a zygote. Sometimes a mutation in DNA can allow an organism to survive; for example, a bird can develop a stronger beak in order to eat a particular seed. Over time, this can lead to a new species. On the other hand, a mutation can lead to an organism's failure to survive, such as an albino deer born in the wild. These organisms often do not survive long enough to reproduce; therefore, their genetics are not passed down to other generations. It is important that DNA is replicated without major mutations in order to ensure the survival of the species. The presence of chemicals can often lead to adverse changes in DNA replication.