Question

echinoderms are called so. give reasons

Answer 1

Some echinoderms have very tightly interlocking plates, like sea urchins. ... In sea urchins and sand dollars, these interlocking plates form an enclosure, almost like a shell, called a test. Sea urchins also have spines protruding from their tests, in life. Others have more movable plates, like sea stars or starfish.

Answer 2

Answer:

Because of spines present on their skin.

Explanation:

Echinodermata are so named owing to their spiny skin (from the Greek “echinos” meaning “spiny” and “dermos” meaning “skin”).