HOW A ZYGOTE OF HEN TAKE OXYGEN THROUGH CALCAREOUS SHELL?
The Porous microstructure of eggshells permits exchange of gases. A normal egg has about more than 7000 pores in it for gaseous exchange.
Mention one example each for animals with chitinous exoskeleton and those covered by a calcareous shell.
In reptiles and birds, the fertilized eggs covered with hard calcareous shell are laid.