The Life Cycle of the Chicken


On which day did God make the chicken?  Genesis 1:24-31

Which came first the Chicken or the Egg?   Genesis 1: 24

The Story of the Egg

Chickens have fathers and mothers just as people do. The father chickens are called roosters. Mother chickens are called hens. Eggs are laid by hens. When a hen lays an egg she is very proud, and she tells everybody about it in a loud voice. This is her way of saying: "Look what I’ve done" And when you stop to think how an egg is made, it’s quite an accomplishment to be able to lay one.

Lets look at the different parts of an egg.    click to make bigger

Think of the different parts as being layers that are added one at a time from the inside out. The egg starts with a egg cell. This is the small, rather tough white you see on the egg. As a yolk passes thought the oviduct, or egg-laying tube, four separate layers are added. All of these parts are kept in shape by two very thin layers of transparent membranes "skin", and finally the shell - is added in turn. And just a few hours before being laid, the egg receives its pigmentation. The pigments are produced in the chicken's body. And because each egg is colored separately, there is a lot of variation even in eggs laid by the same chicken. Each chicken can lay eggs that haven’t been fertilized. But these unfertilized eggs will never develop an amnion, allantois, chorion, or embryo. Most of the chicken eggs you buy in the grocery store are unfertilized eggs.

Lets look at the hen.  click to make bigger

Before it can produce a baby chick, and egg must be fertile. A hen can lay eggs all her life without laying a fertile egg. In order to produce a fertile egg, a hen must have a husband. Most the eggs you buy in the store are unfertile, and would never be a chick.

Let's look at the developing chick and it's parts.

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The egg cell in the fertile egg is the part that becomes the baby. Before the egg is hatched, the baby is called an "embryo"

The embryo must have food while it is growing. It gets its nourishment from the yolk of the egg. That is why the egg cell is always attached to the side of the yolk. A day or two before the chick hatches it pulls what is left of the yolk into it’s abdomen through its umbilical cord. To use as a food source after it hatches.

The egg white is a cradle for the growing embryo. If the egg gets bumped, or moved to suddenly, the soft white around the embryo comes between it and the shell and cushions the shock.

The shell protects them all from being hurt or damaged.  Crack open an egg and see if you can find each part.  You might want to get an egg from a farmer, it has a better chance of being fertile.

Take a magnifying lens and look at the shell, do you see those little holes?  The embryo breathes through these holes. The shell, that looks as though it were solid, is actually porous. That is, there are thousands of tiny holes in it, so small that it is impossible to see them. At the large end of the egg is an air pocket, filled with oxygen.

A fertile egg is so delicate that it can be ruined by small mistakes. Sometimes a perfectly good egg won’t hatch because it has been turned wrong end up, or shaken.

Mother knows best.

A mother hen reaches underneath her body and turns her eggs frequently with her beak. This is because the egg yolk tends to float toward the shell. When the egg lies too long in one position, the white separates and allows the yolk to float through, forcing the egg cell against the shell and killing it. The hen avoids this by changing the position of the eggs. She keep them warm by spreading her feathers over them. She is very careful with them and won’t let anyone else touch her eggs.

When using an incubator at home, eggs must be turned regularly to prevent the yolk from settling to one side and to exercise the embryo. When you turn the egg, the embryo gets it exercise by turning in the shell until its head is upright. Eggs should be turned at least twice a day. At a hatchery they have large incubators which turn the trays which the eggs are in.  3 days before the eggs are to hatch they stop turning them.  The temperature should be kept at 100*.  If you want to hatch chicks at home you can purchase a small incubator and eggs from a school supply store.  And if everything goes right in  21 days you will have new chicks.

Feeding Chicks:

Did you know that chicks and chickens do not have teeth.  They use their gizzard to make their food smaller.  This organ, located just before their stomach grinds the food into smaller pieces for them.  But they need small rocks called grit to help them do this. A chick doesn't need grit till they are about 7 days old.  Then it is sprinkled on their food daily. 

Brooding Chicks

An idea for a small hen house.

God made many different looking chickens.  Some lay more eggs than others some chickens are larger in size.


Take a look at what each part of the Chicken is called.  

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Science projects with an egg.

Naked Egg

Shrinking Egg


    To demonstrate the semi-permeability of the cell membrane.


  • 1 raw egg in its shell
  • 1 jar with a lid.


  • Place the egg inside a jar.
  • Cover the egg with vinegar.
  • Put the lid on the jar
  • Observe immediately and then for the next 72 hours.
  • Keep egg for Shrinking Egg


    Bubbles start forming on the surface of the egg's shell immediately and increase in number with time.  After 72 hours, the shell will be gone.  The egg remains intact because of the thin transparent membrane. The size of the egg has increased.


    The shell of the egg is made of calcium carbonate, commonly called limestone.  When vinegar chemically reacts with limestone, it produces carbon dioxide gas - those bubbles seen on the egg.  The membrane around the egg does not dissolve in vinegar, but becomes more rubbery.  The increased size is due to osmosis, the movement of water through a cell membrane.  Water always moves through a membrane in the direction where there are more dissolved materials, so the water in the vinegar moves through the thin membrane into the egg because the water inside the egg has more materials dissolved in it than does the vinegar.  The contends of the egg stayed inside the membrane because these molecules were too large to pass through the tiny holes.   this selectiveness of materials moving through the membrane is called semi-permeability.


    To demonstrate the semi-permeability of the cell membrane.


  • Corn syrup
  • ruler
  • jar with lid
  • Naked egg


  • Pour corn syrup into the jar until it reaches a height of 3 inches.
  • Carefully place the egg in the jar.
  • Close the lid, and allow the jar to stand undisterbed for 72 hours.


    The egg drastically changes in size and shape.  It has a rubbery outer skin with very little content inside.


      The excess water inside the egg moves through the membrane into the syrup.  The water content outside the egg is much less than inside, thus the water moves out to the egg.  The molecules in the syrup and other materials inside the egg do not move through the membrane because they are too large.  This selectiveness of materials moving through the membrane is called semi-permeability.








Coloring pages:

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  • Decorah Hatchery
  • 201 Awesome, Magical, Bizarre & Incredible Experiments  By: Janice VanCleave   (John Wiley & Sons Inc.)
  • The Egg  By Gallimord Jeunesse  (Scholastic Inc.)
  • Chick Egg Guidebook  By: G.Q.F. Manufacturing Co
  • Who's Hatching    (Scholastic Inc.)
  • Birds, Birds, Birds  By Ranger Rick's Nature Scope  (National Wildlife Federation, 1985)

Other Reading and Videos:

  • Chickens Aren't The Only Ones  By: Ruth Heller   (Scholastic Inc., 1993)
  • Green Eggs and Ham  By: Dr.Seuss  (Beginner Books, Inc., 1960)
  • Big Egg  By Molly Coxe (Random House, 1997)
  • Egg to Chick   By: Millicent E Selsam  (HarperCollins Publishers, 1970)
  • Chicken and the Egg  By: Sesame Street

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