Closed circulatory system is found in

Options

A. Earthworm
B. Arthropoda
C. Unio
D. Leech

Answer

To determine which organism has a closed circulatory system, we can analyze the options provided:

1. **Understanding Closed vs. Open Circulatory Systems**:
- A closed circulatory system is one where blood is contained within vessels, allowing for efficient transport of nutrients and oxygen.
- An open circulatory system, on the other hand, allows blood to flow freely within a cavity, which can be less efficient.

2. **Analyzing the Options**:
- **Option A: Earthworm**: Earthworms belong to the phylum Annelida. Most annelids, including earthworms, have a closed circulatory system where blood is contained in vessels.
- **Option B: Arthropoda**: This phylum includes insects, arachnids, and crustaceans, which generally have an open circulatory system.
- **Option C: Mollusca**: This phylum includes organisms like snails and octopuses. While some mollusks have a closed circulatory system (e.g., cephalopods like octopuses), many do not, particularly the bivalves and gastropods.
- **Option D: Leech**: Leeches are also part of the phylum Annelida, but they have an open circulatory system where blood is not confined to vessels.

3. **Conclusion**:
- Based on the analysis, the organism with a closed circulatory system from the options given is **Option A: Earthworm**.

**Final Answer**: The closed circulatory system is found in **Earthworm (Option A)**.

---