Find the odd one among the following taxa w.r.t presence of double circulation.

Options

A. Pisces
B. Aves
C. Reptiles
D. Mammalia

Answer

To solve the question of finding the odd one among the given taxa with respect to the presence of double circulation, we will analyze each option step by step.

### Step 1: Understand Double Circulation
Double circulation refers to the circulatory system in which blood passes through the heart twice during one complete circuit of the body. This system separates oxygenated and deoxygenated blood, allowing for more efficient oxygen transport.

### Step 2: Analyze Each Taxon
1. **Pisces (Fishes)**:
- Fishes have a single circulatory system. In this system, blood passes through the heart only once during a complete circuit. Therefore, they do not have double circulation.

2. **Aves (Birds)**:
- Birds have a double circulatory system. Their heart is divided into four chambers, which allows for the separation of oxygenated and deoxygenated blood.

3. **Reptiles**:
- Most reptiles have a double circulatory system, although some may have a partially divided heart. Generally, they are considered to have double circulation.

4. **Mammalia (Mammals)**:
- Mammals also possess a double circulatory system, characterized by a four-chambered heart that separates oxygenated and deoxygenated blood.

### Step 3: Identify the Odd One
From the analysis:
- Pisces (Fishes) is the only taxon that does not have double circulation.
- Aves, Reptiles, and Mammalia all have double circulation.

### Conclusion
The odd one out with respect to the presence of double circulation is **Pisces (Fishes)**.

---