Respuesta :
In a "fight or flight" (life or death) situation, the body has to be ready to defend itself. As an example, if someone where trying to kill you, you would be able to run without getting tired. However, to do this your cells would have to go through anaerobic respiration (the creation of ATP without oxygen). It will not yield as much energy as aerobic respiration, and will result in lactic acid build up (which causes cramps), but it will allow you to be able to run or to fight for your life in a critical situation.
I think the reason we are able to produce ATP without oxygen is because what we were running for our lives and had to stop every time our muscles need oxygen. If this was true we would die. So the reason we can produce ATP without oxygen is because it is a survival mode.
