In which of the following pairs , is the ear represented by tympanum ?

Options

A. Fishes and amphibians
B. Amphibians and reptiles
C. Reptiles and birds
D. Amphibians and mammals

Answer

To solve the question "In which of the following pairs is the ear represented by tympanum?", we need to analyze the structure of the ear in different classes of vertebrates.

### Step-by-Step Solution:

1. **Understand the Classes of Vertebrates**:
- The main classes of vertebrates are:
- Fishes
- Amphibians
- Reptiles
- Birds
- Mammals

2. **Identify Ear Structures in Each Class**:
- **Fishes**: They do not have a tympanum or external ear structure.
- **Amphibians**: They have a tympanum which serves as the external ear.
- **Reptiles**: Similar to amphibians, they also have a tympanum that acts as the external ear.
- **Birds**: They lack a tympanum; their ear openings are covered by feathers.
- **Mammals**: They have both a tympanum and an external ear structure called the pinna. The pinna is the main part of the external ear in mammals.

3. **Analyze the Options**:
- **Option 1**: Fishes - No tympanum.
- **Option 2**: Amphibians and Reptiles - Both have tympanum as the external ear.
- **Option 3**: Reptiles and Birds - Birds do not have tympanum.
- **Option 4**: Amphibians and Mammals - Mammals have both tympanum and pinna, but pinna is the main external ear structure.

4. **Conclusion**: The only pair where the ear is represented by tympanum is **Amphibians and Reptiles**.

### Final Answer:
The correct answer is **Amphibians and Reptiles**.