Study the list of organisms below and use them to answer the questions. I-Hydra II-Owl III-Snake IV-Snail The Phylum of the organism labeled IV is

Analyze the question: You're asked for the phylum of organism IV, which is the snail.

Concept: Animals are placed in phyla based on their body structure.

• Coelenterata (Cnidaria): Hydra, jellyfish and sea anemones. They have a hollow body with stinging cells.
• Platyhelminthes: Flatworms such as tapeworm and planaria. They have flat, unsegmented bodies.
• Arthropoda: Insects, crabs, spiders and millipedes. They have jointed legs and an exoskeleton made of chitin.
• Mollusca: Snails, slugs, mussels, oysters and octopus. They have a soft, unsegmented body, usually a muscular foot, and often a hard calcareous shell.

Solution:

1. The snail has a soft, unsegmented body.
2. It moves on a muscular foot.
3. It is protected by a coiled calcareous shell.
4. These are the defining features of Mollusca.
5. Option A is wrong because a snail is not flat-bodied. Option C is wrong because a snail has no jointed legs. Option D is wrong because Coelenterata is the phylum of Hydra (organism I), not the snail.

Answer: B. Mollusca

Tip: Remember "Mollusca = Soft body + Shell + Foot". Snail, slug, oyster and octopus all belong here. For the other organisms in this list, Hydra is Coelenterata, while the owl and snake are both Chordata (the owl is a bird, the snake a reptile).