Which of the following is not a character of reptiles?

Options

A. Body is covered by dry and cornified skin
B. They are poikilotherms
C. Fertilisation is external
D. Heart is three chambered but four chambered in crocodiles

Answer

To solve the question "Which of the following is not a character of reptiles?", we will analyze the characteristics of reptiles and identify the one that does not belong to this class.

### Step-by-Step Solution:

1. **Identify the Class of Reptiles**:
- Reptiles belong to the class Reptilia within the phylum Chordata. They are primarily terrestrial organisms.

**Hint**: Remember that reptiles are classified under Reptilia and are part of the Chordata phylum.

2. **Characteristics of Reptiles**:
- **Body Covering**: Reptiles have dry, cornified skin covered with scales. This adaptation helps prevent water loss.
- **Thermoregulation**: Reptiles are ectothermic (cold-blooded), meaning their body temperature is regulated by the external environment.
- **Reproduction**: Reptiles typically have internal fertilization, where fertilization occurs inside the female's body, providing protection to the developing embryos.
- **Heart Structure**: Most reptiles have a three-chambered heart, with the exception of crocodiles, which possess a four-chambered heart.

**Hint**: Focus on the unique features of reptiles, including their skin type, temperature regulation, reproductive methods, and heart structure.

3. **Analyze the Options**:
- Review the provided options to determine which characteristic does not apply to reptiles.
- For example, if one of the options states that reptiles have external fertilization, this would be incorrect since reptiles primarily exhibit internal fertilization.

**Hint**: Compare each option against the known characteristics of reptiles to identify the incorrect one.

4. **Conclusion**:
- After evaluating the options, the characteristic that does not belong to reptiles is the one that states they have external fertilization. Reptiles predominantly exhibit internal fertilization.

**Final Answer**: The characteristic that is not true for reptiles is "fertilization is external."

### Summary:
- Reptiles are characterized by dry, cornified skin, are ectothermic, have internal fertilization, and mostly possess a three-chambered heart (with crocodiles being an exception). The incorrect characteristic is external fertilization.