This document provides an overview of biological rhythms by discussing 12 topics: 1) Defining biological rhythms and examples like sleep-wake cycles in animals and plants. 2) Historical discoveries in biological rhythms from 400 BC to 2001. 3) Examples of circadian, circannual, and circatidal rhythms in organisms. 4) Zeitgebers are environmental cues that reset biological clocks. 5) The discovery of clock genes in fruit flies, fungi, and humans that control circadian rhythms. 6) Types of disorders related to disrupted biological rhythms like jet lag and shift work disorder.

1. Synopsis:- 1. Introduction
2. Definition
3. Historical perspective
4. Few examples of biorhythms
5. Zeitgebers
6. Biological clock
7. Discovery of clock genes
8. Origen evolution of biological clock
9. Types of biorhythms with example
10.Biological rhythms disorders
11.Conclusion
12.References

2. 1. Introduction:-
. Biological rhythms are an integral part of every day life for most
organisms on earth
. Repetition of same activity of an organism’s in a definite time is called Rhythmicity
.rhythmic behaviour shown by organisms is known as biological rhythms
. . Biological rhythms are studied by chronobiology. These occurs in animal (eating,
sleeping, mating etc) in plants ( (leaf movements, photosynthetic reaction etc)
. The chronobiology is the study of science of life in relative with time
. The paramecium will congregate for reproduction only at certain times of the day,
animals requiring warm temperatures will become active during the middle of the day
. The bird’s sing mostly in the morning and evening; owls ,hyenas , jackals are active ,
monkeys and apes are active during the day time some good examples of biological
rhythms
2. Definition:-
• . Behavioral activities of an organism’s occur at regular interval of time
• A Biorhythms means a periodic occurrence of specific physiological changes in living
organisms.

3. 3. Historical perspective:-
. 400 BC :-Androsthenes (Alexander the great’s scribe) observe that leaves of
certain trees ( Tamarindus indicus ) open during the day and close at night
. In 1820 and 1832 De Marian and De candolle observed the periodic sleep of
leaves of mimosa plants (sleep rhythms)
.In 1880 Charles Darwin Wilhelm preffer (1845-1892) recognised endogenous
nature of some rhythms in plants
. 1948 Dr. Frank announced that organisms which time their cylindrical
activities independently of environmental clause
. Term chronobiology – F. Hallberg
“ Study of rhythmicity in behaviour of organisms related with time”

4. . 1950 – Scientist observe that starling use the sun to migrate their internal
clock reorients them as the sun changes
. 1971 –The first clock gene (per) is identified in fruit flies
. 1978 – The first clock controlling gene (frq) discovered in Neurospora (red
bread mold)
. 1997- The first clock gene is identified in mammals, the mouse clock gene
. 2001 – First human clock gene discovered.A mutation in the hper 2 gene
speed up the circadian clock in people with a rare disorder

5. • 4.Few Examples of Biorhythms:-
• .Flower open in morning and close in evening
• . Polychaete arevicola live in U shaped burrow in sand and carries out feeding
movement even 6-7 minute
• . Mosquito inactive in morning and active in evening
• . House fly inactive in evening and active in morning
• Birds morning singing, migration annually
• Bats nocturnal comes out at dusk for food
• We feel sleepy generally at same time and wake up too
• . Menstrual cycle
• . The paramecium will congregate for reproduction only at certain times of the day
• . Owls, hyenas, jackals active at night whereas deers, monkeys and apes are active
during the day time

6. • 5 Zeitgebers:-
• . The environmental cues that reset a biological clock are known as
zeitgebers
• .The biological rhythms we observe in animals is the result of an
exogenous (external) factor called a zeitgebers, interacting with an
endogenous (internal) factor called the biological clock.
Examplesss:- Light - Darkness
. Warm – cold
Eating –Fasting
. Social contact

8. • 6. Biological clock:- An internal system that controls an organism’s Circadian
rhythms the cycle of behaviour that occurs regularly in a day
• . In mammals the biological clock is located near the point in the brain where
the two optic nerves cross

10. • 7. Discovery of clock gene:-
• The first report that was published identifying clock gene was found in fruit
flies in 1971 by U.S. Genetiest Ron konopka and Seymour Benzer
• scientist have other clock genes their proteins have since been discovered in
Neurospora ( Bread mold) scientist found clock controlling genes called Frq
and protein white collar -1 and white collar -2 that turn on the frq gene
• . In 2001 Yung Hui and his team discovered the first human clock gene
• 8. Origen and evolution of biological clock:-
• It appears that to set the biological clock and run it initially external cycles at
nature played main role.but biological clock of the individual is set ,
maintained and run , it becomes independent of external cues in other words
we can say that during organic evolution the endogenous rhythms remained
in with that at the exogenous cycle such as day , night, annual, seasonal or
tidal cycles
• Repetition of endogenous Cycles ultimately become innate and independent

11. • 9. Types of Biorhythms:-
• .Circadian rhythms:- Circadian rhythm is a natural internal process that
regulate the sleep – wake cycle and repeat regularly every 24 hours
• Eg:- sleep –wake cycle
• Body temperature change
• . Release of hormones such as melatonin and cortisol

12. • A rhythm with a periodicity of 24 hours is called a circadian (from Latin
circa about,dian means day) eg:- sleep wake cycle
. There may be over 100 physiological cycles in human body.
. Circadian rhythms are endogenous
. Circadian rhythms present even in the absence of environmental cues
such as light, temperature or social cues
• Circadian pacemaker Or master clock
. The master clock control Circadian rhythms
. It consists of a group of brain nerve cells in the hypothalamus called
chiasmatic nucleus (SCN)
. The hypothalamus continually measure the light exposure via the retinal
hypothalamic tract and accordingly adjust the timing of the sleep – wake
cycle

13. • Other examples of Circadian rhythms:-

14. • . Circannual rhythms:- Circa – approximately, annual – yearly.
. The biological activities exhibited by organisms repeated year by year is
termed as circannual rhythms.
. There are certain physiological events occuring in many organism’s with an
interval of 1 year or 365 days
. Example:- Migratory bird
• . Every year they fly.Experiments have been carried out in which the bird’s
have been kept in controlled environment without the chance of a disease or
any situation that might cause them to migrate.but still the bird’s showed
migratory behaviour at the same time as they did every year
• . Then there is the breeding cycles of different organism’s. They repeat the
same cycle every year at the same time

16. • . Circatidal rhythms:- The biological rhythms synchronized with the low and
high tides (the alternate rise and fall of the sea due to gravitational pull
excreted by moon ) in the sea are called circatidal rhythms
• Some examples of circatidal rhythms:-

17. • . Semilunar/Circasyzygic rhythms:- The biological rhythms which are
synchronized with the fortnightly cycle of spring tide ( high tide occuring a day or
two after the new or the full moon) and neap tide (low tide which occurs in the
middle of the second and fourth quarters of the moon ) are known as semilunar
clocks
• Eg:- Pariwinkle Littorina rudis show a marked 14.5 day periodicity in it’s
locomotory activity
• .Circalunar rhythms:- Biological clocks which are synchronized with the moon
phases are called circalunar or circasynodic clocks
• A biorhythm that corresponds with the lunar cycle (approximately 29.5 days).
The reproductive cycles of many organisms, especially marine organisms, are
linked to changing levels of moonlight and the tidal cycle.

20. 10. Biological rhythms disorders:-
. Seasonal affective disorder:- SAD is an infradian rhythm disorder SAD
may have disturbance in the melatonin system,sad people show low
mood effects in winter months
. Jet lag influences our endogenous pacemaker.
. Symptoms include tiredness, sleepiness,loss of concentration,
anxiety, depression and irritability
. Shift work disorder:- when a person work outside the typical work day it
causes changes in typical circadian rhythms.
- excessive sleepiness affecting people whose work overlap with the typical sleep
period

21. 11. Conclusion:-
Biological rhythms are the natural cycle it is integral part of our life, biological
cycle of change in our ( Organisms) body’s chemical or functions
They control cycles like rest and alertness, internal heat level, chemical emission,
and then some.
. Chronobiology is the study of science of life in relation with time

22. • 12. Reference:-
- By Reena mathur
- By internet