Question

Compared to platyhelminthes, which physiological problem was caused the cylindrical body of nematodes? How was that problem solved?

Answer 1

Nematodes have cylinder shaped body. For this reason it is impossible for the cells to respirate by simple diffusion among the calls as they are located far away from the exterior.

This problem was solved by presence of fluid filled cavity, the pseudo-coelom. The pseudo-coelom has unique function to distribute the nutrients to the body. It also collects the excretory materials. The pseudo-coelom creates a hydrostatic pressure to maintain the worm like body shape.