Phylum Echinodermata MCQ - Practice Questions with Answers

• The term ‘Echinodermata’ is obtained from the Greek words 'echinos' meaning spiny and 'derma' meaning skin
• This phylum includes sea stars, sea cucumbers, sea urchins, sand dollars, and brittle stars
• These are exclusively marine
• These are triploblastic with a true coelom
• They bear resemblance to chordates as both are Deuterostomes (Mouth develops last) and both show Enterocoelomic development (body development is through gut)
• Examples: Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber) and Ophiura (Brittle star).

Body Plan and Water Vascular System of Echinoderms:

• Adult Echinoderms are pentaradially symmetrical while larvae are bilaterally symmetrical
• Their endoskeleton is made up of calcareous ossicles
• The coelom is modified to form the characteristic ambulacral or water vascular system
• It consists of a central ring canal and radial canals that stretch along each arm
• The tube-feet project from the holes. The tube-feet show contraction and expansion
• The flow of water in water vascular system can be depicted as:

Water enters through madreporite ⟶ stone canal ⟶ ring canal ⟶ radial canals ⟶ ampulla ⟶ tube feet 

• It is used in locomotion, capture of prey, transfer of food and respiration.

Digestion in Echinoderms:

• They have a complete digestive system with mouth located on the ventral side and anus on the dorsal side

Nervous System in Echinoderms:

• They have a simple nervous system with a central nerve ring and five radial rings. There is no grouping of nerves, so brain-like structure is absent

Reproduction and Development in Echinoderms:

• They are dioecious animals. Sexes are separate
• Usually external fertilization takes place
• Development is indirect with the formation of free-swimming larvae
• They also show high capacity of regeneration