In which of the following animals blood from the respiratory organs does not return to heart but goes to tissues directly?

Options

A. Amphibians
B. Fishes
C. Birds
D. Reptiles

Answer

To solve the question, "In which of the following animals does blood from the respiratory organs not return to the heart but goes to tissues directly?" we need to analyze the circulatory systems of the given options: amphibians, fishes, birds, and reptiles.

### Step-by-Step Solution:

1. **Understand the Types of Circulatory Systems**:
- There are two main types of circulatory systems: single circulation and double circulation.
- In single circulation, blood passes through the heart only once during its entire circuit, while in double circulation, blood passes through the heart twice.

2. **Identify the Circulatory System in Fishes**:
- Fishes have a two-chambered heart (one atrium and one ventricle).
- Their circulatory system is classified as single circulation. Blood from the gills (respiratory organs) goes directly to the body tissues without returning to the heart first.

3. **Examine the Circulatory Systems of Other Options**:
- **Amphibians**: They have a three-chambered heart (two atria and one ventricle) and exhibit a double circulatory system. Blood from the lungs returns to the heart before being pumped to the body.
- **Reptiles**: They also have a three-chambered heart (with some having a partial septum) and exhibit a double circulatory system. Blood from the lungs returns to the heart before going to the tissues.
- **Birds**: They have a four-chambered heart and a double circulatory system. Blood from the lungs returns to the heart before being distributed to the body.

4. **Conclusion**:
- The only animal in the options provided that has a circulatory system where blood from the respiratory organs does not return to the heart but goes directly to the tissues is **fishes**.

### Final Answer:
**Fishes**