Food is the most important source of chemical energy for living things. The chemical energy in food is converted, or changed, by the body into moving mechanical energy and heat energy. People have invented ways to use the chemical energy of substances to power machines.
Organism-population-community-ecosystem-biome in that order
<span>C02 regulation, the carbonic acid-bicarbonate buffer regulation, H+ regulation, and gas exchange. These regulations are all done through the circulatory, excretory, and respiratory systems. They are all part of one big function, that is homeostasis.</span>
