Light and Dark Cycles as a Basis of Temporal Organization

  • Abraham HaimEmail author
  • Boris A. Portnov


Different living organisms are active at different times of the 24-h cycle. Results of controlled experiments revealed that living organisms anticipate the time of activity due to the existence of an endogenous biological clock entrained by the exogenous environmental Zeitgeber. Our daily rhythms can thus be described as an orchestra in which the harmony of all instruments is maintained by the single conductor, with our biological clock carrying out such a function. The biological clock also works as a calendar helping living organisms to anticipate seasonal changes and to acclimatize their physiological systems and behavioral patterns to the approaching season. For its temporal organization, the biological clock uses the signals of light intensity detected by eyes, as well as signals of different wavelength.


24-h cycle Biological clock Zeitgeber Daily rhythms Synchronization Biological calendar Seasonal changes Light intensity Light–dark Cycles Light signals Photoperiod 

Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  1. 1.Center for Interdisciplinary Research in ChronobiologyUniversity of HaifaHaifaIsrael
  2. 2.Department of Natural Resources & Environmental ManagementUniversity of HaifaHaifaIsrael

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