NEET 2025 Zoology Question 166 Solution

Echinoderms possess a coelomic hydraulic circulatory network termed the water vascular or ambulacral system:

• • Water enters through a perforated calcareous plate called the madreporite, passes through the stone canal into the ring canal, and travels through radial canals to reach muscular ampullae and tube feet (podia).
• • Hydraulic hydrostatic pressure changes in the tube feet power their coordinated biological functions.

The precise functional roles of the water vascular system:

• • Locomotion: Tube feet adhere to substrata via suction and contraction, propelling the animal forward.
• • Capture and transport of food: Tube feet and ambulacral grooves pry open bivalve prey and convey food particles to the ventral mouth.
• • Respiration: Thin, exposed epithelial surfaces of tube feet and dermal branchiae (papulae) facilitate gas exchange between coelomic fluid and seawater.
• • Hence, statements A (Respiration and Locomotion) and C (Capture and transport of food) are completely CORRECT.

Differentiating physiological systems in Echinodermata:

• • Excretory system: NCERT explicitly emphasizes that an specialized excretory system is completely absent in echinoderms; nitrogenous waste (ammonia) diffuses directly through thin body walls and dermal gills. Thus, any statement including excretion (B and E) is incorrect.
• • Digestive system: Digestion is accomplished by the complete digestive tract (ventral mouth, stomach, pyloric caeca, and dorsal anus), not the water vascular system. Thus, statements D and E are incorrect.

Only Statements A and C are true functions of the water vascular system, corresponding to Option (2).