All cards have a maximum evolution level. For example, Fishing Fighter 2* cards can evolve to Fishing Warrior 3*. That is its final evolution form. Most cards can evolve twice at most. The major exception is the dragon(balance) race, starting at Baby [element] Dragon 2*, evolving all the way up to 8*.
For a full list of evolutions, go to:
http://dragonera.wikia.com/wiki/Dragon_ ... nture_WikiMidas (Howrus) has done a fantastic job of getting almost every card up there. Just scroll down to the Monster Book & Evolution section.