A) true coelom
B) metameric segmentation
C) closed circulation
D) All of the above
Correct Answer: D
Solution :
The nematodes are commonly known as roundworms or threadworm. These are unsegmented, bilaterally symmetrical and triploblastic animals. The body cavity of nematodes is called pseudocoel. It is bounded only on the outside by mesodermal tissue and inside by endodermal epithelium. They have no respiratory and circulatory organs. Annelids are triploblastic, bilaterally symmetrical, segmented animals tube with in tube body plan. These possess well-developed fluid filled coelom. These also have efficient blood vascular system with blood confined to blood vessels. Another evolutionary advancement of annelid over nematode is metameric segmentation.
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