In animal classification, which one of the following given organisms is an example from the phylum Mollusca?

Introduction / Context:
Animal kingdom classification groups organisms into different phyla based on their body plan, symmetry, coelom, and other structural features. Phylum Mollusca includes soft bodied animals that often have shells, such as snails, clams, and squids. Competitive exams commonly ask you to identify which organism among a list belongs to a particular phylum. This question focuses on Mollusca and asks you to pick the correct example from the given options.

Given Data / Assumptions:

• The phylum of interest is Mollusca.
• Options include locust, butterfly, scorpion, and octopus.
• We assume standard zoological classification.
• You are expected to know basic features of each listed animal group.

Concept / Approach:
Molluscs are invertebrates with soft bodies that may or may not be protected by a hard shell. Examples include octopus, squid, snail, and oyster. Locusts and butterflies are insects and belong to phylum Arthropoda. Scorpions are arachnids, another group within phylum Arthropoda. Octopus, however, is a cephalopod mollusc, recognized by its soft body, tentacles, and marine lifestyle. Therefore, among the given options, only octopus belongs to Mollusca.

Step-by-Step Solution:
Step 1: Recall that Mollusca includes snails, slugs, clams, squids, and octopus, characterized by soft bodies and often a mantle.Step 2: Examine option A, locust. It is an insect with segmented body, jointed legs, and exoskeleton, placing it in Arthropoda, not Mollusca.Step 3: Examine option B, butterfly. This is also an insect, again belonging to Arthropoda.Step 4: Examine option C, scorpion. Scorpions are arachnids with jointed legs and exoskeletons, clearly members of Arthropoda.Step 5: Examine option D, octopus. It is a cephalopod mollusc with soft body and tentacles, fitting the Mollusca phylum.Step 6: Conclude that octopus is the correct example of Mollusca.

Verification / Alternative check:
To verify, think of the fundamental differences between arthropods and molluscs. Arthropods have a jointed exoskeleton and segmented body, while molluscs have soft bodies, often with a mantle and sometimes a shell. Looking at the physical appearance of locusts, butterflies, and scorpions, all clearly show jointed appendages and exoskeletons. Octopus does not have such an exoskeleton and is commonly grouped with squid and cuttlefish, which are reduced shell or shell less molluscs.

Why Other Options Are Wrong:
Option A is wrong because locusts are insects and not molluscs. Option B is wrong because butterflies are also insects with features of arthropods. Option C is wrong because scorpions are arachnids, a class within Arthropoda. None of these show the typical soft bodied molluscan plan of octopus.

Common Pitfalls:
Students sometimes focus only on habitat, for example thinking that octopus and fish are in the same group because both live in water, or that butterflies and snails are similar because they can be seen in gardens. Habitat alone is not a reliable indicator of phylum. Instead, pay attention to body structure, presence or absence of exoskeleton, type of limbs, and segmentation. Remembering one or two classic examples of each phylum, such as octopus for Mollusca, helps you quickly answer classification questions.

Final Answer:
Octopus, a soft bodied animal of phylum Mollusca.