Incomplete double circulation is found in which of the following animals?

Options

A. Birds
B. Mammals
C. Birds and mammals
D. Amphibians and reptiles

Answer

To determine which animals exhibit incomplete double circulation, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Double Circulation**:
- Double circulation refers to the separation of oxygenated and deoxygenated blood. In complete double circulation, blood passes through the heart twice during one complete circuit of the body.

2. **Identify the Types of Circulation**:
- Incomplete double circulation occurs when blood does not fully separate into two distinct circuits. This is typically seen in animals with a three-chambered heart.

3. **Examine the Heart Structure in Different Animals**:
- **Amphibians and Reptiles**: These animals possess a three-chambered heart, which consists of two atria and one ventricle. This structure allows for some mixing of oxygenated and deoxygenated blood, leading to incomplete double circulation.
- **Birds and Mammals**: These animals have a four-chambered heart, consisting of two atria and two ventricles. This structure allows for complete separation of oxygenated and deoxygenated blood, resulting in complete double circulation.

4. **Evaluate the Options**:
- The question provides four options:
- Birds
- Mammals
- Birds and Mammals
- Amphibians and Reptiles
- Based on the heart structure and circulation type, the option that correctly identifies animals with incomplete double circulation is **Amphibians and Reptiles**.

5. **Conclusion**:
- Therefore, the correct answer to the question is that incomplete double circulation is found in **Amphibians and Reptiles**.