The development of a chicken egg is similar to that of a human embryo. The growth of the embryo is a complex process with a multitude of stages with a short growth period of 21 days. Embryonic development is vital to the overall development of the chicken. The Chicken The chicken or the Gallus gallus domesticus is a domesticated fowl and a subspecies of the Red Jungle Fowl. The chicken is one of the most widespread and most common domestic animals. Chickens were first domesticated in India for their use of cockfighting in Africa, Asia, and Europe.

Chickens are mostly used as a source of food by the consumption of their eggs and their meat. Chicken themselves are omnivores, surviving on seeds, insects, and sometimes large animals like lizards and mice. Chickens can live for five to ten years but this depends on the breed. A male chicken is called a rooster while the female is commonly called the hen. The rooster or male chickens differentiate from the hen/ female chicken by their pointed feathers on their necks and are also brighter in color than that of the hen. Breed: Sussex The Sussex chicken is a breed with very little purpose.

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The chicken originated in England around AD 43 for the use as a house pet. The chicken itself is found in a multitude of colors ranging from red to silver. This breed of chicken is thought to be graceful with a long prominent back and a rectangular shape. The tail of the chicken stands at a 45° angle from the chicken’s body. The Sussex’s eye color varies based on the color of feathers the chicken has. In darker varieties the eyes of the chicken are red. In the lighter varieties the eye color is usually orange. These chickens also have a single medium sized comb. Most roosters weigh around 9 lbs. while the hens weigh about 7 lbs. The Light Sussex: Description The Light Sussex is a chicken that is a species within the Sussex breed. The Light Sussex is a chicken with a white body and a black tail with black wing tips. The neck of the Sussex is white with black striped throughout. These characteristics make the chicken have a very striking appearance. For the chicken’s caretaker they must be very careful to keep the chicken out of strong sunlight because with strong sunlight the chicken’s color will fade. The Light Sussex: Characteristics The Light Sussex is a bird with few purposes.

Unlike other breeds of chicken, this bird is not used for egg production or meat consumption. This chicken is more of a prize-winning bird because of their broadness. These birds are also used as backyard birds, or pets because of their unaggressive nature. The Light Sussex is a friendly breed if bred without an aggressive gene. These birds are also good foragers and can be easily handled. They have a very curious nature and often follow their caretakers. The bird is adaptable to its surroundings and often tries to camouflage itself to hide from predators. Egg Fertilization

A chicken always starts from an egg and this egg must be fertilized to grow into a chicken. A hen, which is the egg layer, will lay hundreds of eggs weekly whether the eggs are fertilized or not. The unfertilized eggs will look exactly the same as a fertilized egg but these eggs cannot develop chicks and hatch. The unfertilized eggs are the ones found on the shelf of the grocery store. Fertilization of an egg begins with the hen’s reproductive system, which is made up of an ovary and an oviduct. Roosters or the male chicken’s reproductive system contains testes not unlike those of other male mammals.

During mating, which is an affair that lasts thirty seconds, the sperm then leaves the male through the cloaca, which is an opening on the rooster. The sperm then enters the hen through the reproductive tract more specifically the oviduct. The sperm then continues down the reproductive organs of the hen, which takes a week or more to reach the hen’s shell gland. From there the sperm reaches the isthmus, then the magnum and finally the infundibulum. Here is where the sperm awaits the arrival of the eggs in the process of forming.

A hen’s eggs begin as yolks in the ovary and once released they then pass through the infundibulum where the sperm are waiting. There the eggs are fertilized and pass out the chicken the same way the sperm entered but in reverse. The eggs whites gather around the yolk in the magnum, in the isthmus the shell membranes are laid down. The shell then forms and hardens to the shell gland and finally the eggs are ready to be laid. In the morning eggs are laid and after the eggs have been laid the hen is ready to start the process all over again. Incubation

Incubation of an egg determines life or death for the embryo. For natural incubation, a nest box must be made for the hen and a nest for her to sit on. The nest helps keep the eggs from rolling off or separating from each other. The hen will keep the eggs warm and at a certain temperature needed for growth. A hen has the perfect temperature for the egg’s incubation. If the eggs have no hen and need to be cared for by man-made incubation, two factors must be kept in mind. These factors are heat and humidity. For heat, a steady temperature of 95. ° degrees and humidity must be kept at 50%. Each egg in a man made incubator must also be turned over at least twice a day to in sure that each side of the egg gets heat. In each incubator there also must be a proper amount of moisture in the incubator to create humidity. Stage One: Days One – Seven After the hen has laid the fertilized egg, stage one of embryonic development begins. For an egg to hatch, the egg must have a certain temperature and a high humidity to begin stage one. Stage One of development consists of week one or days one through seven.

On the first day of growth, the hours of growth are the most important. On day one, at sixteen hours, the 1st sign of resemblance to a chick embryo is seen. At 18 hours the alimentary tract appears and 2 hours later the vertebral column appears. Between 21 and 24 hours the nervous system begins to form, and then the head begins form along with the eye of the embryo. Day 2 has the most important formation, the heart. At 25 hours the heart begins and form at 25 hours the ear begins to form. Life for the embryo truly begins at 42 hours when the heart begins to beat.

The third day of growth is where major appendages appear. This is the day the nose, the legs and the wings are being to form. On Day 4 the chick turns 90° and lies with its head on the yolk. The heart also continues to enlarge and the mouth, nasal and pits develop. By the end of Day 4 of incubation the embryo has the organs needed to sustain life after hatching. On Day 5 the reproductive organs form, giving the chick a differentiation of sex. Day 6 gives the chick the formation of a beak becoming more visible, and the wings begin to bend at the elbow.

The 6th day also causes the fusion of the allantois to the chorion and the ribs of the chick also begin to form. Day 6 also makes the gizzard and the intestines of the embryo also loop adding to the chicks’ digestive system. On the last day of stage 1 the embryo begins to sprout feather germs only on the tail and the feather papillae appear on the chick’s thigh. This day also sparks the growth of the sciera of the eye and the leg slowly begins to bend at the knee. Stage Two: Days Eight - Fourteen Stage 2 of the embryo's development contains less development of the vital organs and more on physical details.

On day 8 of development, the embryo's nictating membranes begin to form; which are the chick’s inner eyelids. The chick's feather germs become visible on the tail and the bone marrow cavity of the femur begins to form. The embryo's egg tooth also begins to form; a chick’s egg tooth is the structure the chick uses to crack the shell to exit the shell. Day 9 features the formation of the upper eyelids, which begin to cover the chick's eye. On day 9 the kneecaps also form allowing leg movement. Day 10 gives the chick a physical appearance, on this day the class begin to form and the comb become visible.

Day 10 also makes the chick's flight feathers appear and gives the chick feather tracts, which appear over the sternum. The lower eyelids also develop on day 10. Day 11 features physical attributes just like Day 10. Development for Day 11 gives the chicks claws a downward curve and with the claws the chick's feet become padded. The feather germs on the chick's tail and back begin to appear as long tapered cones. The beak of the chick also begins to harden and the embryo begins to draw calcium from its eggshell for the further development of its bones.

On the 12th day of development the embryo's scales appear on its lower legs and movement begins within the shell. This day also give the ribs development causing them to ossify. Day 13th has very little development for the embryo. The fingers of the wings are covered in feather papillae and the embryo's left and right collarbones fuse to form the wishbone. On the 14th day of development all development is given to the embryo's head. The embryo turns it's head toward the blunt end of the egg and the embryo's skull begins to ossify. Stage 3: Days 15-21

The final stage of growth leaves little development for the embryo to go through before it hatches. The first day of Stage 3 or Day 15 makes the chick's scales, claws, and beak firm. On day 16 the embryo turns its beak toward the air cell getting ready for it's final departure. The embryo's shell also gets lined with the choriollantoic cavity. On day 17 the chick goes further into the air cell announcing it is almost time to hatch. Day 18 causes the beak to break through the inner shell membrane, the lungs also begin to function. On day 19 the yolk sac begins to enter the body cavity.

On Day 20, the lungs are using the air cell for breathing completely and the embryo is so large it occupies all the egg except for the air cell. On Day 21 the embryo's neck begins to spasm. Then the egg tooth breaks through the shell. The chick then breaks all the way through the shell and hatches. Conclusion The chicken is a bird that is used for consumption and egg production. The chicken itself comes from an egg with a fertilization process similar to that of other mammals. After an egg has been fertilized the embryo takes approximately 21 days for the full growth period and at 21 days the embryo hatches.