Amphibia shares with reptiles in all of the following characters except -

Options

A. Tympanum represents the ear
B. External fertilization and indirect development
C. Dioecious, oviparous
D. Cold blooded or poikilotherms

Answer

To solve the question "Amphibia shares with reptiles in all of the following characters except -", we will analyze each option provided in the context of the characteristics shared by Amphibia (frogs, toads, etc.) and Reptilia (snakes, lizards, etc.).

### Step-by-Step Solution:

1. **Understanding Tympanum**:
- Both amphibians and reptiles possess a tympanum, which is an external ear structure. This means they share this characteristic.
- **Conclusion**: This option does not differentiate between the two groups.

2. **External Fertilization**:
- Amphibians typically exhibit external fertilization, where fertilization occurs outside the female's body, often in water (e.g., frogs).
- Reptiles, on the other hand, generally undergo internal fertilization, where fertilization occurs inside the female's body.
- **Conclusion**: This is a characteristic that distinguishes amphibians from reptiles.

3. **Indirect Development**:
- Amphibians often have an indirect development process, where they go through a larval stage (like tadpoles) before maturing into adults.
- Reptiles usually do not have this kind of development; they hatch from eggs that are more similar to the adult form.
- **Conclusion**: This characteristic is also not shared between amphibians and reptiles.

4. **Dioecious and Oviparous**:
- Both amphibians and reptiles are dioecious, meaning they have separate male and female individuals.
- Both groups are also oviparous, meaning they lay eggs.
- **Conclusion**: This characteristic is shared between both groups.

5. **Cold-Blooded (Poikilothermic)**:
- Both amphibians and reptiles are ectothermic (cold-blooded), meaning they rely on external sources to regulate their body temperature.
- **Conclusion**: This characteristic is also shared.

### Final Answer:
The characteristic that Amphibia does not share with reptiles is **external fertilization**. Therefore, the correct answer is **B**.