Question

development of chick in detail

Answer 1

The development of the chick begins in the single cell formed by the union of two parental cells, egg and sperm, in the process known as fertilization. In birds, fertilization occurs about 24 hours before the egg is laid.

The newly formed single cell begins to divide into 2, then 4, 8, 16, 32 and so on. At the time of laying, hundreds of cells are grouped in a small, whitish spot (the blastoderm or germinal disc) that is easily seen on the surface of the yolk.

When the egg is laid and cools, division of the cells ceases. After the egg is laid, cooling the egg after the egg is laid does not result in the death of the embryo. It may resume its development after several days of rest if it is again heated by the hen or in an incubator.

Functions of the Embryonic MembranesSpecial temporary organs or embryonic membranes forme within the egg, both to protect the embryo and to provide for its nutrition, respiration, and excretion. These organs include the yolk sac, amnion, and allantois.The yolk sac supplies food material to the embryo. The amnion, by enclosing the embryo, provides protection. The allantois serves as a respiratory organ, gets minerals from the shell, and handles waste. These temporary organs function within the egg until the time of hatching.Several changes take place during the 18th and 21st days. The chick draws what remains of the yolk into its body and "takes its lunch with it" (so-to-speak) when it hatches. Thus, the chick really doesn't need to be fed for the few days after it hatches.The chick's head is under its right wing with the tip of the beak pointed at the air shell. The large neck muscle contracts and forces the egg tooth through the air cell, and the chick takes it first breath. This is referred to as internal pipping. At this time, you may hear the chick peeping inside the shell.On the twenty-first day of incubation the chick finishes its escape from the shell. The egg tooth makes the initial break in the shell. This is referred to as external pipping.The hatching process can last from 4 to 12 hours before the chick breaks free from the shell. The chick, as it appears upon freeing itself from the shell, is wet and very tired. For the next several hours it will lie still and rest. A few hours later the chick, now dry and fluffy, will become extremely active and the egg tooth will dry and fall off.

Answer 2

The chicken (taxon -Gallus gallus) embryo develops and hatches in 20 to 21 days and has been extensively used in embryology studies. Historically, the chicken embryo was one of the first embryos studied, readily available and easy to incubate, embryo development can be directly observed by cutting a small window in the egg shell. A key to this model organism study was the establishment of a staging atlas by Hamburger & Hamilton in 1951 [1], which allowed specifc developmental landmarks to be seen and correlated with experimental manipulations of development. This much cited paper included images of all key stages and was more recently republished in the journal Developmental Dynamics (1993), for a new generation of avian researchers. Probably just as important has been the recent chicken genome sequencing, providing a resource to extend our knowledge of this excellent developmental model.


Fertilized eggs can be easily maintained in humidified incubators and during early stages of development the embryo floats on to of the egg yolk that it is using for nutrition. As the embryo grows it sinks into, or below the, yolk. The regular appearance of somites allowed early experimenters to acurately stage the embryo. The embryo was accessible and easy to manipulate (limb grafts/removal etc) that were informative about developmental processes. Chicken cells and tissues (neural ganglia/fragments) are also easy to grow in tissue culture. The discovery that quail cells have a different nuclear appearance meant that transplanted cells (chick/quail chimeras) could be tracked during development. For example, LeDourian's studies showed how neural crest cells migrate widely throughout the embryo.