Many types of Reptile eggs do not have 'shells' - they are surrounded by a flexible membrane.
This is not brittle so does not crack & is also more permeable than a solid shell.
Reptiles - cold-blooded animals - need far less oxygen than mammals.
eg. many types of reptiles actually bury the egg clutch to protect them until they hatch - they are not exposed to open air at all, but that's how they develop.
http://en.wikipedia.org/wiki/Eggshell#Fi...
http://www.arkive.org/galapagos-marine-i...
Actually, it doesn't matter whether or not an egg is small or large. The egg shell is a semi-permeable membrane, which you seem to already know. But it's only logical to realize that the larger the egg, the more oxygen it can take in at the same ratio of a smaller egg. Oxygen is oxygen and there is an abundance of it everywhere on Earth. There actually used to be so much oxygen at the time of the dinosaurs that insects like mosquitoes were as big as your head because there was so much O2 to be used. Oxygen diffuses through small eggs and just enough is taken in by the fluids to keep the creature alive. Same with a larger egg. Oxygen diffuses through it and it takes in as much as is needed.
If you think large eggs cannot take in enough oxygen, that would be like saying an airplane cannot hold sufficient oxygen to keep hundreds of human beings alive, which isn't the case.
I have a Bachelor's in Biological Sciences, so trust me, I know everything there is to know about osmosis, diffusion, and cellular respiration. Comment back if you'd like to know more.
How did the really large dinosaurs like Argentinosaurus lay eggs? Eggs can only get so large until oxygen can't diffuse through them. From what I read it seems most people believe these dinosaurs slept standing up. If they chose to lay down, could they get back up? If not, how did they lay eggs without them cracking when they hit the floor? This is just one of those questions that kept popping in my head, but I never actually asked it till now. Thanks guys!
