How a Chick Develops From an Egg

The transformation of an egg into a baby chick is a complex and interesting natural process. The development begins with the fertilization of the egg from male sperm, follows with a 21-day incubation period and ends in a hatching process in which the baby chick emerges from the egg.

  1. Fertilization

    • The development of a chick begins with fertilization, or the union between the sperm of a rooster and the egg of a hen. Once the sperm and egg merge, the single cell begins to divide until hundreds of cells gather and form the germinal disc, a small white spot on the surface of the yolk. The hen will then lay the egg and the development of the egg will cease until the chick hatches.

    Embryonic Membranes

    • After the laying of the egg, embryonic membranes, including the yolk sac, allantois and amnion, will form in the egg to not only protect the embryo but to also provide for the embryo's respiration, excretion and nutrition until the hatching process begins. The yolk sac is essential for providing food to the embryo; the allantois functions as a temporary respiratory organ to handle waste and extract minerals from the shell; and the amnion provides protection by enclosing the embryo.

    Incubation

    • The next stage in the development of a chick is the incubation stage, which lasts for three weeks, or 21 days. During the first several days of the incubation period, the embryo begins to grow and develop rapidly inside of the egg. By the 14th day, the fully developed chick begins to move into a hatching position. From the 18th day to the 21st day, the chick draws the remaining yolk into its body and uses a temporary egg tooth to break the egg and take its first breath.

    Hatching

    • On the final day of incubation, the hatching process begins. The hatching process can last up to 12 hours before the chick finishes its escape from the egg. The chick uses its beak to cut through the shell until its head emerges from the shell and it then kicks free from the shell. After the hatching process is complete, the chick will rest for several hours and gradually begin to walk and become active. Within several days, the temporary egg tooth will dry up and fall off the beak.