Does a star fish has shell on its back?

Starfish don't have shells on their backs. They have a tough, hard outer skeleton called an endoskeleton. This endoskeleton is made of calcium carbonate plates, which are connected by flexible tissue.

Here's why it's not technically a shell:

* Location: Shells are external coverings, while the endoskeleton is on the inside.

* Composition: Shells are typically made of calcium carbonate but are often much harder and more rigid than the endoskeleton.

* Function: The endoskeleton provides structural support and protection for the starfish, while a shell would be more for protection from predators.

So, while the starfish's outer covering might seem like a shell, it's actually a unique, internal skeleton that gives it its distinctive shape and allows it to move in its characteristic way.