Question

Explain the general characteristics of the phylum Nematoda and Platyhelminthes.

Answer 1

Phylum Nematoda:

The body is cylindrical and elongated with pointed ends. All the members of nematodes are endoparasites.

Characteristics:

1. They are called roundworms because they appear circular in cross-sections.
2. These are bilaterally symmetrical, unsegmented, and triploblastic animals.
3. These are pseudocoelomates showing tissue level of organization but do not have real organs.
4. These have a flexible body movement.
5. The body wall has longitudinal muscles and an elastic cuticle.
6. Females are longer than males.
7. The mouth has teeth to cut and pierce the tissues of the hosts and the muscular pharynx help to suck the blood from the host.
8. Examples: Hookworm, lungworm, pinworm, threadworm, whipworm, and eelworm.

Phylum Platyhelminthes:

The body of these animals is more complexly designed. The body is bilaterally symmetrical.

Characteristics:

1. These animals are triploblastic, i.e., their body consists of three germ layers.
2. This allows outside and inside body linings as well as some organs. There is some degree of tissue formation. In other words, these animals show organ level of organization.
3. There is no true internal body cavity or coelom. In other words, these are acoelomate animals.
4. Since the body is dorsoventrally flattened, these animals are called flatworms.
5. They are either free-living (e.g., planaria) or parasitic (e.g., liver flukes).
6. The parasitic organisms are provided with hooks for the attachment to the body of the host and suckers for absorbing the nutrients.
7. They are hermaphrodite.
8. Schistosoma is a parasitic flatworm of the Platyhelminthes phylum.