In amphibians the heart is

Options

A. Two chambered and venous
B. two chambered and arterial
C. three chambered
D. incompletely four chambered.

Answer

**Step-by-Step Solution:**

1. **Understanding Heart Structure in Vertebrates:**
- Begin by recognizing that vertebrates have different heart structures based on their classification. For example, fish have a two-chambered heart, while amphibians have a different structure.

2. **Identifying the Heart Structure in Amphibians:**
- Amphibians are characterized by having a three-chambered heart. This consists of two atria (auricles) and one ventricle.

3. **Comparing Amphibians with Other Vertebrates:**
- In contrast, reptiles typically have an incompletely four-chambered heart, while birds and mammals possess a fully four-chambered heart. This comparison helps to clarify the unique structure of the amphibian heart.

4. **Additional Chambers in Amphibians:**
- Besides the main chambers, amphibians also have additional structures associated with their heart, such as the sinus venosus and the truncus arteriosus. These play roles in the circulation of blood.

5. **Myogenic Nature of the Heart:**
- The heart in amphibians is myogenic, meaning that the impulse for heartbeats originates from the heart muscle itself, rather than from the nervous system.

6. **Conclusion:**
- Based on the information gathered, the correct answer to the question is that in amphibians, the heart is three-chambered.

**Final Answer:**
- In amphibians, the heart is three-chambered.

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