Exploring the Unique World of Echinoderms

What makes the skeleton of echinoderms unique compared to other organisms in phylum Echinodermata?

A. Echinoderms have a hard, calcareous skeleton.

B. Echinoderms have an internal skeleton.

C. The skeleton of echinoderms provides body rigidity.

D. The skeleton of echinoderms is not molted.

Answer: B. Echinoderms have an internal skeleton.

Echinoderms, such as sea urchins and sea lilies, possess a unique characteristic in their skeletal structure compared to other organisms in phylum Echinodermata. They have an internal skeleton made up of calcareous ossicles connected by a mesh of collagen fibers.

This internal skeleton provides support and protection for the echinoderms, allowing for their distinct body shapes and movements. Unlike external skeletons that need to be molted as the organism grows, the internal skeleton of echinoderms grows with them, adapting to their changing body size and needs.

The presence of an internal skeleton also contributes to the overall rigidity and strength of echinoderms, enabling them to thrive in diverse marine environments. This unique skeletal structure is a key feature that sets echinoderms apart from other organisms within their phylum.