To tell you the truth I have not gotten to it as yet. It dawned on me just recently though that, to dwell on this topic might in effect raise ones IQ level. When people take such tests often they are not aware of the focus of such tests up front. I believe they are to test for such things as cause and effect recognition, pattern recognition and perhaps even cycles and rhythms. Seems it would be elemental to the development of children as well. As all things are interconnected, correlations are a good thing to focus upon as well, example the correlation of species within a given environment, even ones social correlations, though this be an individual focus and perhaps to complex, but perhaps some general principles could be outlined. I will get around to exploring this, it is a topic I really would like to see take off. PS: It just occured to me that, any arrangement whatsoever if repeated is pattern, disorder, chaos might be then arrangement without repetition, though in a complex order, disorder might me simply be a breakdown both of order and/or repetition.
By taking the two words and breaking them down into their separate meanings a definition of biological rhythms evolves as, life which involves a recognizable pattern of change over time. There are two major categories of biological rhythms, endogenous, and exogenous. Endogenous rhythms come from within and are regulated by the organism itself, for example the body temperature cycle. Exogenous rhythms are the result of external factors, such as a change in the seasons, or the transition from day to night. Environmental stimuli that help to maintain these cycles are called zietgebers, which comes from German and translates as "time givers." Zietgebers include sunlight, noise, food, and even social interaction, all cues that help the biological clock maintain a 24-hour day.
There are four categories of biological rhythms that extend beyond just classifying them based on internal and external sources. This system maintains that criteria, but extends to include the duration of the cycle as a defining factor. The resulting categories are circadian rhythms, diurnal rhythms, ultradian rhythms, and infradian rhythms.