A Circadian Rhythm is...
¨Circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment.¨
What is it, you ask?
A circadian rhythm is controlled by your biological clock and produced by natural factors in your body. It is your daily routine, including eating patterns and sleeping patterns. Your circadian rhythm is affected by light and other natural factors.
Mankind's circadian rhythm depends mainly on light. People who work night shifts can work to alter this rhythm, but still face challenges with light during the day, for your body sends out chemicals when your circadian rhythm knows it's daytime.
Fruit flies are a good example of circadian rhythms for they hatch in mornings. Although no acquired learning is done yet, their circadian rhythm is at work here.
Don't think light affects you? It sure messes with your circadian rhythm, that's for sure. Blind people's circadian rhythms are often very messed up. Many blind feel tired and sleepy during the day, and can't seem to get to bed at night. Many find taking Melatonin supplements to help, which are artificial supplements of the chemicals your circadian rhythm gives your body when it's time to sleep.
Norwegian researchers studied arctic animals and their circadian rhythms, and found that they only show the rhythms 3 out of the four seasons. During summer, there is constant light, and these animals show little signs of circadian rhythms.
In mammals your circadian clock controls your metabolism, which is how fast you digest food and turn it into energy. This controls eating patterns in animals, for the body knows when it is morning and is time to get on the hunt for food in order to survive. Trust me, the body knows!!