Also known as FIV or cat AIDS, feline immunodeficiency virus is an infectious disease caused by a retrovirus belonging to the lentivirus family. It is in the same family as the feline leukemia virus (FeLV), and is similar to the HIV virus in humans. FIV infects both domesticated cats, lions, tigers, pumas and cheetahs.
This map only incorporates the wide-open throttle condition, but adding a third independent axis of throttle position can create a 3D performance map; it is noted that throttling directly affects efficiency via an inverse proportion, and maximum efficiency and minimum BSFC is realized at 100% throttle.
Indeed, it is not a law, but rather an average observation. The main point is that efficiency is <100%, meaning that energy is lost at every transfer. The level of efficiency varies according to trophic level, and functional group (as noted by Armand Kuris), e.g. ectotherms are generally more efficient than endotherms.