What do cuticles do for land plants that was not necessary for ancestors that lived in water?

 Cuticles help land plants conserve/retain water—or, help prevent excessive "water loss".

They keep the water in kind of like barriers. The ancestors that lived in water did not need cuticles because they were in water almost 24/7

Atp is is our little "pocket" of energy. of course, if you have too little, then it means you have too little energy, and you'll pass out. the way to not have enough, is to have no energy sources (glucose, fats, proteins). you can't have too many atp molecules. cycles like the krebs cycle produce it, but if you have too much of any substrate (or too little for that matter), the cycle stops and atp is no longer made (it stops until substrate levels are such that the process can go on). in any case, this is unlikely since atp is constantly hydrolyzed and remade, even while you're asleep. you won't have too much. if you have zero, you are dead or dying.