Identifying Animals in the Phylum Mollusca

The question asks to identify an example of an animal belonging to the phylum Mollusca from the given options. The phylum Mollusca is one of the largest phyla of invertebrate animals. Molluscs are known for their soft bodies, although many possess a hard shell. They have a unique structure called a mantle, which is a fold of tissue that covers the body and secretes the shell. They also typically have a muscular foot used for movement and a radula, a structure used for feeding.

Examining the Options

Let's look at each option to determine which one fits the description of a mollusc:

• Octopus: Octopuses are marine invertebrates. They have a soft body and a mantle. While most molluscs have external shells, octopuses are cephalopod molluscs that have either a reduced internal shell or no shell at all. They move using a form of jet propulsion or crawling with their arms, which are derived from the foot.
• Scorpion: Scorpions are arachnids, which are arthropods. Arthropods are characterized by having an exoskeleton, segmented bodies, and jointed appendages. Scorpions do not have the soft body, mantle, or typical foot structure of molluscs.
• Locust: Locusts are insects, also belonging to the phylum Arthropoda. Like scorpions, they have an exoskeleton, segmented bodies, and jointed legs and wings. They are distinctly different from molluscs.
• Prawn: Prawns are crustaceans, another group within the phylum Arthropoda. They have a hard exoskeleton and segmented bodies, unlike molluscs.

Comparing Mollusca and Arthropoda

It's helpful to compare the key characteristics of the phylum Mollusca with the phylum Arthropoda, as many options belong to the latter.

Conclusion

Based on the characteristics of the phylum Mollusca and the comparison with Arthropoda, the Octopus is the only animal among the options that is classified as a mollusc. Scorpions, locusts, and prawns are all arthropods.

Therefore, the example of the phylum Mollusca is the Octopus.

Revision Table: Key Phyla Examples

Additional Information on Mollusc Diversity

The phylum Mollusca is incredibly diverse and includes several major classes:

• Gastropoda: Snails, slugs, sea slugs. They usually have a single shell (or none) and move with a muscular foot.
• Bivalvia: Clams, oysters, mussels. They have two hinged shells and are filter feeders.
• Cephalopoda: Octopuses, squids, cuttlefish, nautilus. These are marine predators with well-developed heads and eyes. Their foot is modified into arms and tentacles. Shell is often reduced or absent (like in octopus and squid) or external (like in nautilus).
• Polyplacophora: Chitons. They have eight shell plates.
• Scaphopoda: Tusk shells. They have a tubular shell.
• Monoplacophora: Primitive molluscs with a single shell.
• Aplacophora: Worm-like molluscs without shells or distinct feet.

The octopus, being a cephalopod, is a highly evolved mollusc, adapted for active predation. Its soft body and lack of a prominent external shell are adaptations for agility.