Teaching The Life Cycle of a Chicken

Overview: The purpose of this lesson is to introduce the students to the stages in the lifecycle of a chicken.The students will learn how chickens progress from egg to chick, and observe eggs as they hatch.

During this unit study, my kiddos observed the fertilized chicken eggs, they will observed the incubation and hatching process, made predictions, and described what they observe in their Life Cycle journals.


They labeled egg diagrams, wrote a summary of the life cycle of a chicken and drew pictures for each stage, and drew and labeled a sequence of events chart that showed the steps an egg goes through to hatch into a chick.They also observed the incubation and hatching process and describe what they saw in their journals.

  • Incubator
  • Fertilized chicken eggs
  • Chicken embryo development chart
  • Magnifying lens
  • Journals.

Lesson Introduction

What is an egg?

Where do eggs come from?

What does a bird have to do to hatch an egg?

What happens when an egg hatches?

What is a life cycle?

Exploring the Lifecycle Concept

Pass around an egg for the kiddos to examine. 

Use a magnifying lens to look at the shell, and have the kiddos describe what they see. One will see little holes in the shell. Ask what they think the holes are for, and explain that the shell is porous (has thousands of tiny holes), and that the embryo breathes through these holes.

Take a boiled egg and cut the egg open to show the different parts of the egg, and explain the function of each part. 

The yellow yolk is the food the growing chick embryo would eat.

The white/clear albumen provides additional food and water, as well as a protective cushion for the growing chick.

The hard shell also protects the chick embryo.

Have the kiddos make their own eggs with construction paper (yellow and white).

What is a mammal, and how is it different from an animal that lays eggs?

What are some other animals that lay eggs?

Identify and talk about egg-laying animals such as amphibians, reptiles, birds, fish, octopuses, snails, spiders, and insects.

The children will draw and label a sequence of events chart that shows the steps an egg goes through to hatch into a chick.

Development of the egg: The Yolk:

The chicken egg starts as an egg yolk inside a hen. A yolk (called an oocyte at this point) is produced by the hen's ovary in a process called ovulation.

Growth of the Embryo: 

As the embryo grows, its primary food source is the yolk.  The exchange of oxygen and carbon dioxide gas occurs through the eggshell; the chorion lines the inside surface of the egg and is connected to the blood vessels of the embryo.

A chick emerges after a brief three weeks of incubation.


On the second day of incubation, the blood islands begin linking and form a vascular system, while the heart is being formed elsewhere. By the 44th hour of incubation, the heart and vascular systems join, and the heart begins beating. Two distinct circulatory systems are established, an embryonic system for the embryo and a vitelline system extending into the egg.

At the end of the third day of incubation, the beak begins developing and limb buds for the wings and legs are seen.

On the fourth day, the chick's entire body turns 90 degrees and lies down with its left side on the yolk. The head and tail come close together so the embryo forms a "C" shape. The mouth, tongue, and nasal pits develop as parts of the digestive and respiratory systems. The heart continues to enlarge even though it has not been enclosed within the body. It is seen beating if the egg is opened carefully. The other internal organs continue to develop. By the end of the fourth day of incubation, the embryo has all organs needed to sustain life after hatching, and most of the embryo's parts can be identified. The chick embryo cannot, however, be distinguished from that of mammals.

Fifth day, the formation of reproductive organs and differentiation of sex.

Sixth day is the beginning of the beak.

The embryo grows and develops rapidly. By the seventh day, digits appear on the wings and feet, the heart is completely enclosed in the thoracic cavity, and the embryo looks more like a bird.

Eighth day, the chick is beginning to get feathers.

After the tenth day of incubation, feathers and feather tracts are visible, and the beak hardens.

On the fourteenth day, the claws are forming and the embryo is moving into position for hatching.

Sixteenth day, the scales, claws and beak becoming firm and horny.

Seventeenth day, the beak turns toward air cell.

On the nineteenth day the yolk sac begins to enter body cavity

After twenty days, the chick is in the hatching position, the beak has pierced the air cell, and pulmonary respiration has begun. The yolk sac completely drawn into body cavity; embryo occupies practically all the space within the egg except the air cell.

After 21 days of incubation, the chick finally begins its escape from the shell. The chick begins by pushing its beak through the air cell. The allantois, which has served as its lungs, begins to dry up as the chick uses its own lungs. The chick continues to push its head outward. The sharp horny structure on the upper beak (egg tooth) and the muscle on the back of the neck help cut the shell. The chick rests, changes position, and keeps cutting until its head falls free of the opened shell. It then kicks free of the bottom portion of the shell. The chick is exhausted and rests while the navel openings heal and its down dries. Gradually, it regains strength and walks. The incubation and hatching is complete. The horny cap will fall off the beak within days after the chick hatches.

When using an incubator, 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.  3 days before the eggs are to hatch, you should stop turning them.  The temperature should be kept at 100 degrees F.  In 21 days, you will have new chicks.

After 21 days, the chick hatches out of the egg. Chickens are precocial, which means they are born able to feed themselves almost immediately.The newly hatched chicks wander around and start to feed themselves by pecking at seeds, rocks, and insects. The chicks start to grow, and after a few weeks they are called a poults.