NEET BIOLOGY

Detailed explanation-1: -A third group of triploblasts has a slightly different coelom lined partly by mesoderm and partly by endoderm. Although still functionally a coelom, these are considered “false” coeloms, and so we call these animals pseudocoelomates. The phylum Nematoda (roundworms) is an example of a pseudocoelomate.

Detailed explanation-2: -Animals possessing Coelom are called coelmates. Coelom is cavity between alimentary Canal and body wall enclosed by mesoderm on both sides.

Detailed explanation-3: -Pseudocoelomates are animals with a fluid-filled body cavity not completely lined with mesoderm tissue. The cavity is in between the mesoderm and the endoderm and is called a pseudocoelom (Fig. 3.17 B). The roundworms (phylum Nematoda) are examples of pseudocoelomates.

Detailed explanation-4: -Hint: When the body cavity is completely lined with mesoderm, the body cavity is called a true coelom and the animals are called coelomates.

Detailed explanation-5: -This body cavity is partially lined with the mesodermal derivative cells. Here, the coelom is much reduced or lost. It is not considered a true coelom, and hence the name pseudocoelomates. Examples include rotifers, priapulids and nematodes (roundworms).