During a recent 737 simulator recurrency session, the F/O was asked to conduct the whole start up procedure from dark cockpit to engines running all by himself without another crew member to prompt or help in any way. Without the use of a checklist he was completely out of his depth. It proved that he used checklists as a crutch for his lack of knowledge. He already had over 500 hours on type.. Areas of responsibility are fine until you are asked to know what is the other fellows area of responsibility as well.