Trace the sequence of events that lead to development of a chick from the fertilised egg of a hen.
After fertilisation, the zygote starts dividing and moves down the oviduct. As it moves down, a number of protective layers get formed around it. The egg shell is one of these protective layers. It is deposited around the egg in the lower part of the oviduct of the hen, just before the egg is laid. The embryo develops inside the egg for around 21 days, after which the chick gets fully developed. During the incubation period, the eggs require a specific temperature; this is provided by the hen by sitting on the eggs. Finally, the egg shell breaks down and the chick comes out.