Chronobiology examines periodic phenomena in living organisms and their adaptation to solar and lunar rhythms. Biological rhythms vary from milliseconds to years and regulate essential processes like eating, sleeping, and cell regeneration in animals, and leaf movement and photosynthesis in plants. The most important rhythm is the circadian rhythm, which has been observed in plants, animals, and microbes. The history of chronobiology includes early observations of daily leaf movements and flower opening patterns. In the 20th century, scientists isolated clock genes in fruit flies and discovered their role in circadian rhythms.

1. Dr. Jeni Padua, PhD.
Visiting Researcher, Universidad de Santiago de Compostela, Lugo,Spain
Erasmus Mundus Euphrates Fellow, European Commission
Indian Science Academies’ SR Fellow-CCMB, Hyderabad
Dean of Sciences, Holy Cross College, Nagercoil, India.

2. CHRONOBIOLOGY
• Chronobiology is a field of biology that examines periodic(cyclic)phenomena in
living organisms and their adaptation to solar and lunar related rhythms.
• These cycles are known as biological rhythms.
• Biological rhythm varies from milliseconds in ocular field potential to years
• The variation of the timing and duration of biological activity in living
organisms occur for many essential biological processes.

3. BIOLOGICAL RHYTHMS OCCUR
1. In animals (eating, sleeping, mating, hibernating, migration,
cellular regeneration etc.)
2. In plants (leaf movements, photosynthetic reactions etc.)
3. In microbial organisms such as fungi and protozoa.
The most important rhythm in chronobiology is the circadian
rhythm.

4. HISTORY OF CHRONOBIOLOGY
• In 4th Century BC, Androsthenes (Ship
captain of Alexandar the Great)
described diurnal leaf movements of the
Tamarind tree.
• In 13th Century, Noon and Midnight
Manual (Chinese) literature mentioned
the Circadian or diurnal process in
humans.

5. • In 1729, Jean-Jacques d Ortous de Mairan a French scientist noted 24-hour
patterns in the movement of the leaves of the plant Mimosa pudica.

6. • In 1751, Carlous Linneaus
(Swedish Botanist and naturalist)
designed a flower clock using
certain species of flowers.
• By arranging the selected species
in a circular pattern, he designed
a clock that indicated the time of
day by the flowers that were
open at each given hour.

7. •In 1832, de Candolle discovers that the Mimosa opens it’s leaves
1-2 hours earlier each day.
•In 1896, Patrick and Gilbert observed that during a prolonged
period of sleep deprivation, sleepiness increases.
•In 1906, Simpson and Gailbraith found the daily temperature
rhythms in monkeys persist in constant darkness.

8. • In 1918, J.S. Szymanski showed that animals
are capable of maintaining 24-hour activity
patterns in the absence of external cues such
as light and changes in temperature.
• In 1922, Richter showed the persistent
rhythms of activity in animals (rats)
• In 1959, Franz Halberg (University of
Minnesota - Father of American
Chronobiology) coined the term “Circadian”.

9. • In 20th Century, Auguste Forel, Oskar Wahl
noticed Circadian rhythms in the rhythmic
feeding times of bees.
• In 1967, Erwin Bunning described
physiological clock in plant.
• In 1970s, Ron Konopka and Seymour Benzer
isolated the first clock mutant in Drosophila and
mapped the “period" gene, the first discovered
genetic component of a circadian clock.

11. •In 1984, the first clock gene was thereby
isolated and its structure was
molecularly characterized.
•In 1994 Michael Young discovered a
second clock gene, timeless, encoding
the TIM protein that was required for a
normal circadian rhythm

12. THANK YOU
Dr. Jeni Padua, PhD.
Visiting Researcher, Universidad de Santiago de Compostela, Lugo,Spain
Erasmus Mundus Euphrates Fellow, European Commission
Indian Science Academies’ SR Fellow-CCMB, Hyderabad
Dean of Sciences, Holy Cross College, Nagercoil, India.