Serious question about bird eggs?

Question

My wife says eggs "breathe" oxygen through pores in the egg shell. I say they don't. Which one of is right? Please give an explanation.

Answer 1

I'll try to keep this short. I can get quite long winded :-)

Eggs, when they form inside the hen, are covered with calcium that is pulled from the blood stream. These pores in the hen's uterus help create a pattern of calcium placement around the yolk and white. The placement of calcium differs from species to species and is so unique that paleontologists can tell what species of dinosaurs laid what eggs.

The layering of calcium around the softer sections of the egg is not perfect, creating an uneven layer that is a patchwork of calcium and spaces. These spaces -'holes'- are what evolved to help oxygen enter the egg. They also help carbon dioxide leave the egg. It's possible that the egg evolved from a soft gelatin-like structure (as in fish and amphibians) to a skin like covering. To add extra protection and to prevent the loss of moisture, the gelatinous egg developed a leathery outer lining. Part of this was to help the egg survive out of water. Fish don't have to worry about their eggs surviving out of water because their offspring live IN water. No need to protect the white and yolk from dehydration. From the leathery shell we go to the calcified hard egg, which is even better adapted to preserving moisture. It's well known that birds can lay eggs in much drier environments than reptiles can. Part of this is because bird eggs can convert some of their yolk into moisture. It's also due to the hard outer egg shell. The 'pores' in the bird shell are probably the evolutionary remnants of the pores in the leathery shells of species past. Despite all this, there's more calcium to pores. One species of bird only has 20% of its shell surface devoted to pores.

Another reason why these pores exist: When the egg is laid, moisture is needed to prevent the embryo from sticking to the sides of the shell. If there's too much moisture, the embryo will drown and die. They get this moisture from the air and from the hen's feathers. Many species of bird will lay in water to moisten their bellies before returning to the nest. Humidity is also important for the developing chick. Too much humidity kills the chick. Too little and the membranes that surround and protect the chick become tough and the chick cannot penetrate the leather-like structures during hatching. The result, if this happens, is called a DIS - 'Dead in shell'.

I hope I've helped the argument somewhat, LOL! :-)

Answer 2

I am sorry to say that your wife is right and here is why and where I found it :

Shell structure
Eggs are usually smooth, but there are exceptions. A cormorant's egg, for example, is quite rough and is very chalky. In contrast, tinamous have very shiny eggs, and ducks have oily and waterproof eggs. Another variation is the very heavily pitted eggs of cassowaries.

There are tiny pores in the shells of eggs to allow the unborn animal to breathe. The domestic hen's egg has around 7500 pores.

http://en.wikipedia.org/wiki/The_biology_of_eggs

Answer 3

Your wife is most certainly correct.
Eggs breathe through pores on the shell.
Mothers rotate these eggs to ensure proper development, and proper incubation and dispersment of heat.
If the eggs couldn't breathe, they would not be viable.