Schlera
The thick outer covering you are refering to is called the cell wall found in plant cells. I dont know why they have it I guess its just there.
A seals outer covering is thick skin.
Protoplasm
cuticle is the thick layer outside the leaf to prevent loss of water.
The muscular structer that grinds soil is the gizzard.
Cacti have thick stems and skins because they need to store water over long periods of time, and the liquid would evaporate quickly in deasert conditions.
The Statue of Liberty outer covering or skin is copper?
they have pretty much the same skin as most sea mammals , it like a natural wet suit.
The thick outer layer of a plant cell is called the cell wall... 8) A.I
The spiny anteater, correctly known as the echidna, has a thick layer of fur, through which hundreds of sharp quills grow.
In a rainforest what is the thick layer of treetops called?
vitreous humor