Respuesta :

It is an example of circadian rhythm.
It is indeed a circadian type of rythm but let me explain it a little bit more.This kind of biological rythm displays an endogenous, entrainable oscillation of about 24 hours. These rhythms are driven by a circadian clock, and rhythms have been widely observed in plants, animals, fungi and cyanobacteria.The fall of cortisol levels fit perfectly this description