Question

Eggs with tough protective shells developed to

Answer 1

They developed to be protected by the hard shell from parasites and ther predators.

Answer 2

While observing the egg from the external one can witness shell, that is, a hard, protective covering formed of calcium carbonate. The shell is porous, and thus, it permits the transfer of gases via the shell. The moisture and carbon dioxide are given off via the pores and are substituted by atmospheric gases like oxygen.  

The eggs with tough protective shells are developed to safeguard the egg from germs, parasites, and predators.