I have the answer: – In summary to the below;-
Hens will lay eggs even without mating with a rooster. These eggs are used for marketing and for our consumption, those that we buy in supermarket.
For eggs to hatch into a baby chick, you require the rooster to mate the hen, and fertilised it in order for the egg to incubate!
the scientific reply
Submitted by Brian from Chesterfield, Missouri
From a biological point of view, how is chicken-egg harvesting accomplished?
Does the female require fertilization before the egg is laid?
When and how is fertilization accomplished?
How many eggs can a chicken normally lay in a 24-hour period?
How does the process differ if the desire is to produce chickens rather than eggs as a food source?
Dennis Chang, graduate student and HHMI predoctoral fellow at Harvard University
Let me begin with the fertilization of eggs in the mating of a rooster with a hen.
Birds, like mammals, use internal fertilization.
Many species of birds lack a penis; instead, the male just has a genital opening (cloaca), which must be positioned against the female’s genital opening (also called a cloaca) for sperm transfer.
Male chickens, however, do have a small penis to facilitate mating. In any case, after copulation, which only lasts a few seconds, the sperm quickly swim up the oviduct toward the ovary. The sperm can stay alive in the oviduct for several weeks, ready to fertilize the next egg cell (oocyte) that appears.
Oocytes are produced in the ovary, packaged with yolk within a thin protein membrane, and released one at a time into the funnel-like infundibulum of the oviduct. The oviduct is a tubular passageway leading from the ovary to the outside world. It is also an assembly line in which the various layers of the egg are constructed. After an oocyte-yolk package is released into the infundibulum, it lingers there for about 20 minutes.
If sperm are present, then the oocyte is fertilized and becomes an embryo. But if no sperm are around (that is, if the hen has not mated), then the egg still proceeds down the assembly line of the oviduct. In this assembly line, albumen (egg white) is added around the yolk, shell membranes are added, and the shell itself is constructed. Finally, the complete egg is pushed through the vagina and out the cloaca.
If the egg has been fertilized, then the embryo inside has already divided several times but remains a group of unspecialized cells. When the egg is incubated at about 37 to 38 °C, the embryonic cells differentiate to form a chick, which will hatch after 21 days. If the egg has not been fertilized, then the oocyte within will never grow or divide, and the egg will never hatch. The eggs you buy at the supermarket are eggs that have never been fertilized.
Domestic chickens lay one egg every 26 to 28 hours (about one egg a day) for a period of 4 to 6 days. In between periods of egg laying, the hen rests. Wild birds may rest for months before laying more eggs, but domestic hens, specially bred for abundant egg production, may rest for as little as 1 day between egg-laying periods. Note that hens will lay eggs even without mating with a rooster.
Commercially, if the goal is to produce eggs, then hens are kept away from roosters, and eggs are collected as they are laid. If the goal is to produce poultry meat, then hens are mated with roosters, and the eggs are incubated to give rise to chicks. Of course, even a farm that produces only eggs will need to have some matings to replace the hens that grow too old to lay eggs.