Lark or Owl? How our biological clocks work?

Lark or Owl? How our biological clocks work?

What is the biological clock?

The biological clock is a system in every living organism’s body that regulates our daily activities. Some people also call this system as the Circadian Rhythm or Circadian biological clock. Circadian means almost a day. In turn, this includes all human activities and conditions during a 24-hour cycle of a day. Our biological clock never stops running. It is like a clock that ticks every second of a day without stopping.

The main mechanism that controls all the activities of a person’s biological clock is the Suprachiasmatic Nucleus, in short SCN. SCN is a part of the hypothalamus and it has 20000 nerve cells in it. These nerve cells get the light from the retina part of the human eye. After, they send a signal to the brain to regulate sleeping hours. So, we can say that the human brain controls our circadian clock.

Influence of biological clock on our organism

This timing mechanism could determine and arrange various parameters in human bodies. For example, sleep cycle, breeding and eating habits, and psychological conditions. It starts working with the daylight and gives the message to our brain in order for us to wake up. At this time, the melatonin level in the human body gets lower and the cortisol level in human body increases.

During the day, especially in the afternoon, we have the most active body clock because of hormone releases that our biological clocks start functioning. At night, with the disappearance of daylight, our hormone levels start changing. Thus, melatonin starts increasing, while cortisol decreasing. Accordingly, it gives the essential signal to our bodies to relax and sleep.

Lark or Owl? How our biological clocks work?

That is how our biological circadian clock works on a regular day. Yet, any kind of irregularity in our rhythm can result in serious problems that would end up in severe diseases and illnesses. A person, whose biological rhythm malfunctions, can have health issues.

Consequently, it may lead to depression, sleeping disorders, heart disease, obesity, and diabetes. These are only some of the problems a person with a disrupted circadian rhythm could come across.

Why do different people have different types of biological clocks?

Biological clock determines our sleep and wakes to upcycle and the main factor that controls it is the sunlight. Notably, many people have different sleep cycles. Some of us are larks that go to bed, when the sun disappears. Larks have a good night’s sleep between 6-9 hours. Also, they wake up with the sun and start the day refreshed.

But there are also many individuals who have the same sunlight during the day. Though, they are always awake after midnight watching TV, working or studying with their eyes wide open. They might wake up later than us or wake up even at the same time for us. It doesn’t mean all of them have a sleeping disorder. This is totally normal thing for  owls.

There are many external factors that determine our biological clock and sometimes we just live with it comfortably. However, it might be a painful way of life for the others. Even partners living in the same house, sleeping on the same bed could have different sleep/wake up cycles. And in some circumstances that is totally normal.

Sleepy students sitting on the classesChanges in circadian rhythm

Biological clock can cause health problems when it is changed by sudden. If the process is quite smooth, then you can change your biological clocks. The American organization Rand Company has calculated that getting up too early for classes costs the state $9 billion a year. The reasons of this phenomenon are accidents of sleepy students and poor academic results.


When we look at the factors that cause people to have a different biological clock, we could say that the biggest reason for this is genetics. The biological clock is something that humans take over from their ancestors through genes.

So, if one individual has a morning person genetics, the other could have evening person kind of biological sleeping pattern. That is also the same for other behaviors and habits. Since we inherit that from our elders, it would not be a huge problem for us to live in that cycle and behave accordingly.

Geographical features

Geographical features of a region can affect our biological clock drastically. For example, it is too hard to sleep at night for an individual in humid areas. At the same time, another person could just enjoy it and feel more relaxed. Furthermore, people living in different parts of the world with different amounts of sunlight could have different cycles.

In some countries, people see the sunlight only for a few hours a day. Because they are used to it, they don’t end up getting obese or depressed all the time. Of course, this is totally an individual thing and it could be vice versa for another person.


Another significant reason for having different biological clocks is the great change that we are going through in our daily lives. The first change starts with aging. Aging affects our biological clock deeply as a result of the time periods of hormone releases in our body. The time of melatonin and cortisol releases are not the same for a teenager and an adult.

Researches have shown that the release of melatonin in a teenager’s body occurs hours later, than the release of the same hormone in an adult’s body. It would naturally cause the teenager to sleep late. Though, because he/she has to go to school early in the morning, his/her sleep cycle would be disrupted with stress.

Man's hand holding glass of beer, watching football match on TVVarious life conditions

When it comes to talking about changes, it is impossible not to mention the changes in our daily lives. These changes sometimes lead us to have different biological clocks. With the changing work hours and night shifts, some people need to go to work at night. As a result, this will cause them to have a different biological clock.

Also, the rising stress level in our daily lives could cause us to have insufficient sleep, thus changing our biological rhythm. Of course, it isn’t always about work or stress, sometimes it is all about fun.

Take for instance the differences between the time zones. Notably, some people wake up in the middle of the night to watch games and shows. As a consequence of this, their biological clock changes sharply.


These are some of the reasons for some of us becoming owls while the others are just larks. Although some consider having a different biological clock as a negative thing, it is obvious that sometimes it is just a natural condition. Take into account the specific needs of your organism. In order to change circadian rhythm, it’s necessary to be patient. Remember that drastic changes are harmful for your health. 

Recommended articles: Ten Simple Tips to Help You Fall Asleep FasterHow to Rest Properly


Please enter your comment!
Please enter your name here