Endotherms, such as birds and mammals, use metabolic heat to maintain a stable internal temperature, often one different from the environment. Ectotherms, like lizards and snakes, do not use metabolic heat to maintain their body temperature but take on the temperature of the environment.
It attempts something else to reach the same end product.
Plants cell unable to do photosynthesis use the reaction from our cells creating ATP. There are some other examples I'm sure but I can't remember them of the top of my head.
