,BIOLOGICAL RHYTHMS
• Living organisms have evolved under constantly changing
environment due to the daily and yearly revolution of earth that
has driven the development of biological rhythms.
• Biological rhythms are cyclical changes that exist at genetic,
physiological and behavioral levels across taxa which enable the
organisms to predict and adapt to variety of climatic conditions.
• Based on the time scales, these are categorized as circannual,
circalunar, circatidal, infradian, ultradian and circadian rhythms.
, Biological Rhythms
Cyclic pattern of physiological changes or changes in activity most often synchronized with daily,
monthly, or annual cyclical changes in the environment.
Ultradian Less than 24 hour (h).
Rhythms Arenicola marina (lug worm) - feed on surface every 6-8 minutes
Circatidal Synchronized with tidal flow ( approximately 12.4 h)
Rhythms Crabs – times activity cycles to match tidal flow
Circalunar Synchronized with lunar cycles (29 days).
Rhythms Marine worm Platynereis sp. – Maturation and Spawning
Circannual 1 year long.
Rhythms Bird migration
More than 24 h
Infradian
Rhythms Human menstrual cycle
Circadian Endogenous, entrainable rhythms with a period close to 24 h
Rhythms 3
• Living organisms have evolved under constantly changing
environment due to the daily and yearly revolution of earth that
has driven the development of biological rhythms.
• Biological rhythms are cyclical changes that exist at genetic,
physiological and behavioral levels across taxa which enable the
organisms to predict and adapt to variety of climatic conditions.
• Based on the time scales, these are categorized as circannual,
circalunar, circatidal, infradian, ultradian and circadian rhythms.
, Biological Rhythms
Cyclic pattern of physiological changes or changes in activity most often synchronized with daily,
monthly, or annual cyclical changes in the environment.
Ultradian Less than 24 hour (h).
Rhythms Arenicola marina (lug worm) - feed on surface every 6-8 minutes
Circatidal Synchronized with tidal flow ( approximately 12.4 h)
Rhythms Crabs – times activity cycles to match tidal flow
Circalunar Synchronized with lunar cycles (29 days).
Rhythms Marine worm Platynereis sp. – Maturation and Spawning
Circannual 1 year long.
Rhythms Bird migration
More than 24 h
Infradian
Rhythms Human menstrual cycle
Circadian Endogenous, entrainable rhythms with a period close to 24 h
Rhythms 3
