How does variation occur?

Variation or mutation occurs within the DNA. It is a natural result of the replication process, or the copying of one DNA strand to make new DNA during reproduction. If the new mutation ends up making some kind of variation that does not kill the organism, then the variation will be passed on to new generations. This is how new traits are formed. When the variation is actually more useful than a trait that the organism's parents had, that new variation will be passed along as a survival trait.