All of them are characters of reptiles except

Options

A. Lizards shed their scales as skin cast
B. Scutes are present on their body
C. Heart is three-chambered in all reptiles
D. They are poikilotherms

Answer

To solve the question "All of them are characters of reptiles except," we will analyze each option provided in the context of reptilian characteristics.

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for the option that does not represent a characteristic of reptiles. We need to evaluate each option carefully.

2. **Evaluate Option 1**:
- **Statement**: "Lizards shed their scales as skin cast."
- **Analysis**: This statement is true. Lizards, like other reptiles, undergo a process called ecdysis, where they shed their skin and scales.
- **Conclusion**: This is a characteristic of reptiles.

3. **Evaluate Option 2**:
- **Statement**: "Scutes are present on their body."
- **Analysis**: Scutes are indeed a type of scale found on the skin of many reptiles, including turtles and crocodiles.
- **Conclusion**: This is also a characteristic of reptiles.

4. **Evaluate Option 3**:
- **Statement**: "Heart is three-chambered in all reptiles."
- **Analysis**: Most reptiles have a three-chambered heart (two atria and one ventricle). However, crocodiles, which are reptiles, have a four-chambered heart.
- **Conclusion**: This statement is incorrect because it does not apply to all reptiles.

5. **Evaluate Option 4**:
- **Statement**: "They are poikilotherms."
- **Analysis**: Poikilotherms are organisms whose body temperature varies with the environment. Reptiles are indeed poikilothermic (cold-blooded).
- **Conclusion**: This is a characteristic of reptiles.

6. **Final Conclusion**: After evaluating all options, the only statement that does not hold true for all reptiles is option 3: "Heart is three-chambered in all reptiles." Therefore, this is the correct answer to the question.

### Answer: Option 3 (Heart is three-chambered in all reptiles)

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