Chicken or the egg?

Spring is finally here!

Grape Hyacinths © Agnes Becker

Over the Easter weekend I have been thinking about how a chick develops in an egg, known as embryogenesis. Of course, the egg has to be fertilised which the eggs you ate over Easter won’t have been. It takes just 21 days from the day a fertilised egg is laid until the chick is ready to hatch.

Chicken egg development day 10 illustration © Agnes Becker


Chick illustration © Agnes Becker
So far I have only been able to get my information from wikipedia and youtube but what I have found is incredible.

Did you know?

  • It takes 4 hours for the chicken to make the inside of the egg, and 20 hours to create the shell
  • The yolk sac (yellow bit in an egg) eventually is absorbed by the chick
  • There is a membrane containing a something called allantoic fluid which helps the chick to breathe in the egg and collects fluid waste from its kidneys
  • The calcium in the shell of the egg is absorbed by the chick to make its bones

The egg also contains amniotic fluid, just as in the human womb, to keep the growing embryo stable whilst it grows.

I won’t give it all away yet, not least because I need to check with a poultry scientist that what I have found online is actually correct (if anyone reading this know about chick embryogenesis please get in touch!), but I hope to have this card out when I do my big batch of card printing in a couple of months.

In the meantime, watch this video on a chick developing inside an egg:

Which came first?

As to this question, I am getting very confused! The chicken evolved from non-chicken ancestors through genetic mutations occurring in the development of the sex cells. The sex cells from the non-chicken ancestors with the mutation lead to a chicken developing in the egg, rather than a non-chicken ancestor. But the chick embryo is inside the egg. If a chicken isn’t classed a chicken until it has hatched, then I guess the egg came first? But if the egg was laid by a non-chicken ancestor, then is the egg actually a chicken egg? I guess it depends on how you define the egg and the chicken…

What do you think?


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