Question

Echinoderms have been a successful lineage since their appearance in the Cambrian period, though as adults are arranged differently from many of their close relatives. Describe ways in which echinoderms differ from other deuterostome animals?

Answer 1

Deuterostomes are group of animals in which the first opening in the embryo becomes the anal opening . It includes chordata, Echinodermata and Hemichordata. Echinoderms are spiny skinned organisms ( Greek word, echinos means spiny and dermos means skin ). They are exclusively marine organisms with triploblastic symmetry. First members of this phylum apeared during Cambrian period. Examples- Sea stars, sea cucumber, brittle stars...Echinoderms are different from other deuterostomes in different ways,

* presence of water Vascular system in Echinoderms which help in gaseous exchange, locomotion and feeding.

* Respiration through tubefeets and gills. In Hemichordata respirtion is through gills; in chordates respiration is through lungs, skin, gills.

* Poorly developed sense organs in echinoderms.

* Echinoderms are exclusively marine organisms. Hemichordates live in burrows and chordates in different habitats.

* Nervous system present with a nerve ring and radial nerve cords. But brain is absent. Hemichordata have a primitive nervous system and chordata have dorsal, hollow, single nervous system.

* Locomotion with help of tubefeet.

* Presence of calcerous spicules all over body surface.

* Star shaped body ,Unsegmented.

* Larval forms shows bilateral symmetry and adult forms show radial symmetry. Hemichordates and chordates are bilaterally symmetrical.

* Echinoderms have the ability of regeneration.

* Presence of toxic cells in body of echinoderms.

* Presence of podocytes in echinoderms , cells that filter body fluids.

* Madreporite is the calcerous opening use to filter water into water vascular system.