NEET BIOLOGY

Detailed explanation-1: -Additionally, sea cucumbers, brittle stars, and sea lilies, less known animals of the ocean, round out the family tree. Together, these animals make up the Echinodermata, a word with Greek origins meaning “hedgehog skin.” Echinoderms live in every ocean, even off the coast of Antarctica.

Detailed explanation-2: -Echinoderms are named for the spines or bumps covering the outer surface of the bodies of many of them (Greek root word echino-meaning spiny; Latin root word-derm meaning skin). Examples of echinoderms include sea stars, sea urchins, sea cucumbers, brittle stars, and feather stars (Fig.

Detailed explanation-3: -Sea cucumbers differ from other echinoderms in having an elongate, cylindrical body with the mouth and anus at opposite ends. Because their body is muscular and soft rather than spiny, sea cucumbers are sometimes confused with sea slugs (snail relatives that lack a prominent shell).

Detailed explanation-4: -These squishy invertebrates are echinoderms, making them distant relatives to starfish and urchins. Unlike starfish or sea urchins, the bodies of sea cucumbers are covered with soft, leathery skin instead of hard spines.

Detailed explanation-5: -The water vascular system includes a number of small tube feet that become stiff when water is pushed into them, allowing the sea star to move on a conveyor belt-like rotation of feet. Although brittle stars also have a water vascular system, they twist and bend their long arms to move, instead.