Absence of circulatory system in Hydra is compensated by

Options

A. pseudocoelomic fluid
B. gastrovascular cavity
C. presence of tentacles
D. None of these

Answer

To solve the question regarding how the absence of a circulatory system in Hydra is compensated, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Hydra's Anatomy**:
- Hydra is a simple, aquatic organism belonging to the phylum Cnidaria. It has a basic body structure that lacks complex systems like a circulatory system.

2. **Identifying the Function of Circulatory Systems**:
- In more complex organisms, the circulatory system is responsible for transporting nutrients, gases (like oxygen and carbon dioxide), and waste products throughout the body.

3. **Examining Hydra's Alternative Mechanisms**:
- Since Hydra lacks a circulatory system, it must rely on other structures to perform similar functions.

4. **Gastrovascular Cavity**:
- Hydra possesses a gastrovascular cavity, which serves multiple functions: digestion, nutrient absorption, and gas exchange.
- The gastrovascular cavity is filled with a fluid that allows for the distribution of nutrients and gases to the cells lining the cavity.

5. **Gas Exchange in Hydra**:
- Oxygen from the water diffuses into the gastrovascular cavity, where it can be absorbed by the cells.
- Similarly, carbon dioxide produced by cellular respiration diffuses out of the cells into the cavity and is expelled into the surrounding water.

6. **Conclusion**:
- The absence of a circulatory system in Hydra is effectively compensated by the gastrovascular cavity, which allows for nutrient absorption and gas exchange.

### Final Answer:
The correct answer is **B. Gastrovascular cavity**.

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