The most advanced kidneys in which loop of Henle is present are called metanephric kidneys, these are found in all, except one

Options

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

Answer

To solve the question regarding the presence of metanephric kidneys, we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Kidneys**:
- There are two main types of kidneys: metanephric and mesonephric.
- Metanephric kidneys are the most advanced type and contain a structure known as the loop of Henle.
- Mesonephric kidneys are considered primitive and do not have a loop of Henle.

2. **Identify the Organisms**:
- The question lists four groups of organisms: amphibians, reptiles, birds, and mammals.
- We need to determine which of these groups does not possess metanephric kidneys.

3. **Analyze Each Group**:
- **Amphibians**: They typically have mesonephric kidneys, which are primitive and lack a loop of Henle.
- **Reptiles**: They possess metanephric kidneys, which are advanced and include a loop of Henle.
- **Birds**: They also have metanephric kidneys with a loop of Henle.
- **Mammals**: Like reptiles and birds, mammals have metanephric kidneys that include a loop of Henle.

4. **Conclusion**:
- Since amphibians are the only group listed that has mesonephric kidneys and lacks the advanced metanephric kidneys, they are the exception.
- Therefore, the answer to the question is **amphibians**.

### Final Answer:
The correct answer is **amphibians** (Option A).

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