Breathing is a physiological process of gas exchange that is remains one of the primary qualifiers that describe a living organism. While observing the giant space amoeba discovered in 2268, Doctor Leonard McCoy described it as a very simple form of life capable of displaying almost all the functions living organisms perform, including the ability to breathe, eat and reproduce. (TOS: "The Immunity Syndrome" ) A low respiratory rate was one of an injured Pavel Chekov's symptoms in 1986. (Star Trek IV: The Voyage Home) Not all humanoids breathed the same, for example: , "A Matter Of Honor" )