Biological Clock


When the sun rises on a warm and sunny day you can see the trumpet-shaped flowers of the morning glory open up. When they close late in the afternoon primrose flowers open and before daylight arrives the next morning they close again.

Biological rhythms, like the opening and closing of flowers happen all over nature. But not all of them are daily rhythms. Some, like the beating of our heart, occur every second. Other rhythms are based on months, seasons or years.

Scientists use the term biological clock to describe the timing that controls biological rhythms. But what is this clock and where can you find it? In animals it is probably controlled by the brain, but in plants and other living things that have no brain it must be something else.

The biological rhythms of seashore organisms are connected to the rise and fall of the water. When the tide comes in they open their shells and get food, when the water goes back the shells close to protect the animals from the dry air.

Bay of Funday High Tide Bay of Funday Low Tide

Bay of Funday - High and Low Tide -  Samuel Wantman


The migration of animals is also an event that happens when a signal is sent out. When days become shorter birds leave the northern parts of the world and fly south where it is warm and they have enough food. In the summer they fly back to have babies .

Humans also have biological clocks that control their daily rhythms. Body temperature, blood pressure , sleeping and waking up have a 24-hour rhythm. Many illnesses have a yearly rhythm. Colds and flus often happen in winter. Measles occur mostly during the spring and summer.

When people travel by plane from one continent to another they often cross many time zones. Their internal clocks don’t seem to work correctly. We call this jet lag. It makes you feel tired and it takes many days for your body’s biological clock to get used to the new place.

People who work night shifts also have problems with their biological clocks. In general, they may not be as alert or active as people who work during the daytime . They also have more accidents during work. Sometimes they have more health and sleeping problems than other people.

By using the right medicine you can fight off problems that are connected with different times of day. Heart attacks and strokes often happen in the morning hours—between the time you get up and noon. Asthma often occurs between midnight and the morning hours. So when people with weak hearts take their medicine right after waking up it might prevent a heart attack.

Biological clocks control many rhythms of life. We are learning more and more about these rhythms. Doctors are looking for new ways to make travelling more comfortable and medical treatment more effective.


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  • alert = watchful, aware and ready to act
  • asthma = a disease in which you have problems breathing
  • based = have a basis, come from
  • biological clock = the system in plants and animals that controls when they sleep, eat, produce babies etc..
  • blood pressure =the force or power with which blood travels through your body
  • brain = the organ inside you head that controls how you think, feel and move
  • connected = to have something to do with
  • daily = every day
  • effective = successful, useful
  • fight off = to get rid of something
  • flu = illness that makes you tired and cough. Sometimes you get fever
  • heart attack = if your heart suddenly stops working
  • humans = people
  • in general = usually, most of the time
  • internal = inside your body
  • measles = a disease in which you have fever and red spots on your face and body ; children often have measles
  • migration = when birds or animals travel from one part of the world to another
  • morning glory = a plant that has white, pink or blue flowers that open up in the morning and close late in the afternoon
  • primrose = a small wild plant with yellow flowers
  • protect = defend, guard
  • rhythm = if something happens regularly, like every minute or every day
  • night shift = when people work during the night
  • occur = happen
  • prevent =to stop something from happening
  • rise = go up
  • seashore = near the sea
  • scientist =a person who is trained in science
  • time zone = a place in the world that has its own time
  • shell = the hard outer part of an animal or living thing
  • stroke =when a blood vessel in your brain suddenly breaks or becomes blocked so that blood can no longer flow through
  • tide = when water rises and falls
  • treatment =something that is done to help or cure an ill person
  • trumpet-shaped = it has the form of a trumpet
  • weak = not strong