Question

ASSERTION: Water vascular system is the characteristic of echinoderms.
REASON : Main function of the water vascular system is locomotion.
A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C Assertion is correct but Reason is incorrect.
D Both Assertion and Reason are incorrect.

Answer 1

Hint: Echinoderms simply mean spiny or prickly. They possess an internal skeleton also known as endoskeleton made up of calcareous ossicles embedded in the skin. Echinoderms have a tube within the tube body plan and evolved along the deuterostome evolutionary line.

Complete step by step answer: Water vascular system is the most distinctive feature of the Echinoderms. It is the modification of coelom, which consists of a system of canals filled with watery fluid. Various types of canals together form the water vascular system. This system consists of a perforated plate (pore bearing plate) which allows seawater to enter in the system. This plate is known as madreporite. Madreporite opens into the pentamerous ring canal through a stone canal. From every angle of the ring canal, a radial canal arises and runs along the length of each arm.
Lateral canals arise from the radial canals which end in the tube feet. These tube feet are the tube-like appendages. Each arm consists of two double rows of tube feet. Each tube foot consists of three different parts. First is the ampulla, which is a rounded sac-like structure. The second part is called a podium, it is a middle tubular part and the third part is the sucker, which is a cup-like structure.
Water vascular system performs various functions such as locomotion, capture and transport of food and respiration. During respiration, tube feet serve equivalent to the gills.
Hence, the correct answer is option A.

Note: This system in Echinoderms is called the water vascular system because this system acts as the circulatory system for maintaining the continuous flow of water in and out of the body. Adult echinoderms have pentamerous radial symmetry, and hence, ring canals present at the centre of the body have pentamerous structure.