送交者: xh 于 2005-3-17, 15:10:31:
回答: Why we breathe oxygen: 由 AI 于 2005-3-17, 14:44:41:
but I think that we are looking from different perspective.
The flow of energy that you have explained fits the principle nicely.
What I tried to point out is that other energy forms other than food (green plants) can be used in life forms as well. We breath oxygen because we eat food. It is not necessary for someone to eat food, hence breath oxygen.
On the other hand, the flow of energy seems really nice and simple. But in an animal, it envolves lots of different enzymes and steps. That is an example of the complexity that I mentioned. If the whole thing were designed, it might be more simple and efficient. We just do not know enough of the evolutionary history of the pathway yet.