Question

Which of the following classes of Mollusks is exclusively marine?
A. Monoplacophora
B. Amphineura
C. Scaphopoda
D. All of the above

Answer 1

Hint: Mollusca is the second largest phylum of the world with about 160,000 species. Mollusks are soft-bodied animals with an outer protective hard shell-like covering. The exoskeleton of mollusks is made up of calcium carbonate.

Complete answer: Monoplacophora: Monoplacophora consists of organisms with segmented bodies. These are exclusively marine animals. They consist of five pairs of nephridia. The larva is the trochophore larva. These organisms consist of a single shell. An example of a monoplacophora is Neopilina.
-Amphineura: Amphineura is a member of the phylum polyplacophora. In this phylum, the shell is made up of eight to ten small plates. This is also an exclusively marine phylum. An example of polyplacophora is Chiton.
-Scaphopoda: These are the organisms with a hard shell. This is an exclusively marine phylum. Members of scaphopoda have tentacles. They have a digging mouth. These animals come overland sometimes. An example of scaphopoda is Dentalium or Elephant tusk shell.
Thus, based on the above information we can conclude that Monoplacophora, Amphineura, and Scaphopoda are classes of Mollusks that are exclusively marine.
Hence, the correct answer is option (D).

Note: The phylum Mollusca is divided into six classes based on the locomotory structures and the shells. These six classes are as follows –
1. Monoplacophora
2. Polyplacophora
3. Scaphopoda
4. Gastropoda
5. Bivalvia
6. Cephalopoda
-Gastropoda: It consists of organisms with a torsion formed around their body. It is the largest class.
-Bivalvia: It consists of organisms with the dual shell. These organisms do not have any eyes, or tentacles, or jaws, or mouth. They have a siphon for the mouth.
-Cephalopoda: It consists of organisms with no shell. These organisms have ink glands and siphons.