Question

In Molluscs, the digestive tract is
A. Absent
B. Complete
C. Incomplete
D. None of the above

Answer 1

Hint: Mollusca is a phylum of the kingdom Animalia. It is the second-largest phylum in the world. It has about 160,000 species. Molluscs are soft-bodied animals that have a protective covering of calcium carbonate.

Complete answer: The mollusks have a triploblastic organization. This means that they have three germinal layers. They are schizocoelomate organisms. This means that these organisms possess a true coelom that is formed by the splitting of the mesoderm. These organisms have a tube within a tube body organization. This means that they have a complete alimentary canal with two different openings for the mouth and anus. They have a protostome condition. This is the condition when the blastopore during the embryonic stage in the blastocoel first forms mouth and then anus. These organisms have bilateral symmetry which means that their bodies can be cut into two symmetrical halves from only one plane. The bodies of these animals can be divided into three main parts that are the head, visceral hump, and foot. They have an exoskeleton that is in the form of a shell. They have an open type of blood circulation with hemocyanin that is blue in colour. Thus, based on the above information we can conclude that in molluscs, the digestive tract is complete.
Hence, the correct answer is option B.

Note: The Gastropoda class of the phylum Mollusca is an exception with respect to the symmetry. Gastropoda organisms have an asymmetrical symmetry. These organisms have a torsion formed around their body. Moreover, it is the largest class of the phylum Mollusca.