An adaptation occurs when a species is set through a new constraint. This can be change in climate, defense mechanisms, food source, etc. Which will have to occur before an adaptation is made. For an example: in North America the climate slightly swifted. This meant smaller mammals such as rabbits would need to have a thicker coat of fur or shelter. Let's say all the thin furred rabbits died and all that remained were the thick furred rabbits. Over a span of time the rabbits have adapted through the climate. Meaning most of the population is thick furred through their DNA. Conclusively, it's a genetic characteristic that can happen very rapidly or slowly.
