1. BIOLOGICAL RHYTHMS: IT’S A MATTER OF TIME Text: Rhythms of Life Russell Foster and Leon Kreitzman

2. What are Biological Rhythms? What are Rhythms?

3. Pattern Sequence Regularity Progression Time Measure Beat What is a rhythm?

4. Rhythm = sequence of events that repeat themselves in the same order and with the same time interval, over and over again. Biological rhythm: a biological event or function with a pattern of activity that is repeated over and over again at a constant time interval.

6. Biological Rhythms Heart rate Breathing Hormone secretion Menstrual cycle Body temperature Sleep/wake cycle Time What are examples of Biological Rhythms?

7. Biological Rhythms are the product of an internal biological timekeeping system which is controlled by a biological clock Chronobiology

8. Two Broad Categories of Biological Rhythms high frequency – Ultradian Those that have a constant relationship with environmental rhythms – Have a geophysical counterpart

9. ENVIRONMENTAL RHYTHMS Semi-Daily Rhythms Tidal Daily Rhythms Solar Monthly Lunar Quarterly Seasons Annual Longer than a year

10. Spinning of earth on its axis 24h – solar day Movement of earth around sun 365 days – year Tilting of earth on its axis seasons Movement of moon around earth 24.53 days – lunar month 24.8h – lunar day Geophysical

11. Types of biological rhythms with a geophysical counterpart: Period Length Name Chronobiological Name Example 12.4 htidalCIRCA TIDALcrab activity on shoreline 29 daysmonthlyCIRCA LUNARmenstrual cycle, marine reproduction. 365 days yearlyCIRCANNUALHibernation, many reproductive cycles. 24 hdaily CIRCADIAN (circa + diem) sleep-wake cycle and many others infradian

12. What Kind of Organisms Have Biological Rhythms?

13. What is the purpose of having a biological timekeeping system? Promotes organism’s ability to survive by coordinating its activities with changes in the environment Coordinates internal processes

14. STROMATOLITE

15. Many organisms have several kinds of biological rhythms

16. Alexander the Great 4 th Century BC Tamarind Tree

17. de Mairan, 1729 endogenous

19. Du Monceau 1759 Circadian rhythms do not depend on temperature changes Linneaeus 1751 Circadian rhythms are genetically determined

20. Linneaeus 1751

21. de Candolle 1832 When not exposed to environmental day/night rhythms plant leaves opened and closed on a 22 – 23 h cycle instead of a 24 h cycle Free-running rhythm

22. Circadian rhythms are endogenous. Endogenous rhythms are not exactly 24h. The periods of Circadian rhythms are genetically determined. Endogenous rhythms are temperature-compensated

23. Bees – 1910 Forel 1929 Beling 1950s Renner Drosophila – 1950s Pittendrigh

24. PACEMAKER TARGET TISSUE BIOLOGICAL RHYTHMS (overt rhythms)

25. ZEITGEBER TRANSDUCER PACEMAKER INTERMEDIATE ELEMENTS TARGET TISSUES BIOLOGICAL RHYTHMS Endogenous, free-running rhythm

26. Activity (locomotor) rhythm

27. Chronobiology Biological rhythm Ultradian Infradian Circadian Circatidal Circalunar Circannual Endogenous Free-running Pacemaker Target tissue Overt rhythm Nocturnal Diurnal LL DD LD 12:12 Study of biological timekeeping Cyclical, repeated variation in a biological function High frequency – repeats many times in a day Repeats at intervals much longer than 24 hours Approximately a day (24 hours) Approximately every 12.4 hours ( with the tide) Approximately once a month Approximately once a year Internally generated rhythm Not synchronized to external signals A structure that generates a rhythm Tissue whose function is regulated by the pacemaker A visible, measurable rhythm Active at night Active during the day Constant light Constant darkness 12 hours of light; 12 hours of dark