Open vascular system is absent in

Options

A. Housefly
B. Cockroach
C. Silver Fish
D. Earthworm

Answer

**Step-by-Step Solution:**

1. **Understanding Vascular Systems**: There are two main types of vascular systems in animals: open and closed. An open vascular system allows blood to flow freely within the body cavity, while a closed vascular system confines blood within vessels.

2. **Identifying the Organisms**: The question provides four options: housefly, cockroach, silverfish, and earthworm. We need to determine which of these organisms does not have an open vascular system.

3. **Analyzing Each Option**:
- **Housefly**: Houseflies have an open circulatory system where blood (hemolymph) flows freely in the body cavity.
- **Cockroach**: Cockroaches also possess an open circulatory system, similar to houseflies.
- **Silverfish**: Silverfish, being arthropods, have an open circulatory system as well.
- **Earthworm**: Earthworms have a closed circulatory system, which means their blood is contained within vessels.

4. **Conclusion**: Since the question asks for the organism that lacks an open vascular system, the correct answer is the earthworm. Earthworms have a closed circulatory system characterized by blood vessels, a heart, and capillaries.

5. **Final Answer**: The open vascular system is absent in the earthworm (option 4).

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