In which class of vertebrates 3-chambered heart is found?

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the class of vertebrates that possesses a three-chambered heart.

2. **Identifying the Classes of Vertebrates**: Vertebrates are divided into several classes, including Fish, Amphibians, Reptiles, Birds, and Mammals.

3. **Analyzing Heart Structure in Vertebrates**:
- Fish typically have a two-chambered heart.
- Amphibians have a three-chambered heart.
- Reptiles generally have a three-chambered heart, with the exception of crocodiles.
- Birds and mammals have a four-chambered heart.

4. **Conclusion**: The class of vertebrates that primarily has a three-chambered heart is **Reptilia**. However, it is important to note that crocodiles, which belong to the Reptilia class, have a four-chambered heart, making them an exception.

### Final Answer:
The class of vertebrates that has a three-chambered heart is **Reptilia**.

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