Stellar Habitable Zones, Radiation and Circadian Rhythms

Astrobiologists theorize that conditions for life as we know it must be withins the bounds of an approximate conformal mapping to conditions upon our own home planet.  Asking appropriate questions as to what precisely constitutes necessary such bounds seems to be paramount. One of the components that is putatively an invariant property of life is circadian rhythm. This rhythm is in evident quasi-coherence with the diurnal rotation of this planet. How would life change if  the other necessary conditions were extant upon another habitable planet but instead of  our speed of rotation there were a faster or slower one? Would this somehow impact how beneficent capture and utilization of stellar radiation is achieved by alien life forms? Indeed, what if we confirm some sort of capture of the radiative spectrum in an unfamiliar bandwidth and manner by some process or group of processes that evinces a separate and evolving organisation? Does this constitute life?