Animal Physiology - 

Physiology is the science of the functioning of living systems. It is a subcategory of biology. In physiology, the scientific method is applied to determine how organisms, organ systems, organs, cells and biomolecules carry out the chemical or physical function that they have in a living system. The word physiology is from Greek φύσις, physis, "nature, origin"; and -λογία, -logia, "study of". Physiology is a scientific study of the ways in which the bodies of living things work.