From what I understand, Id is just the basic desires, the simplist functions of an animal. Eat, Reproduce, Rage/Attack/Defend.
Ego is all your memories, your feelings, fears, wants, personality, etc. Its what makes you, well, you. Without one you could survive, because your survival is based off of your Id. You would need an ego to survive in a society, but without one its not really considered living by most human standards.
You would be as basic as possible without one, kind of what most people think about animals, that they can't really think for themselves they just exist with no being nor thought. This is what makes us different, we have egos (or atleast we generally believe animals don't have egos).