Define double circulation. Give a comparative account of heart in reptiles, birds and mammals. (IAS 2021/20 Marks)
Define double circulation. Give a comparative account of heart in reptiles, birds and mammals. (IAS 2021/20 Marks)
Double Circulation:
Double circulation is a crucial concept in the field of biology and physiology. It involves the circulation of blood through the heart twice in one complete cycle, ensuring that oxygenated blood is delivered to the body's tissues and deoxygenated blood is returned to the lungs for reoxygenation.
- Pulmonary Circulation: Blood flows from the heart to the lungs for oxygenation and returns to the heart.
- Systemic Circulation: Oxygen-rich blood is pumped from the heart to the body and deoxygenated blood returns to the heart.
Comparative Account of Heart in Reptiles, Birds, and Mammals
| Feature | Reptiles | Birds | Mammals |
|---|---|---|---|
| Chambers | Three-chambered heart (two atria, one ventricle), except crocodiles which have four chambers. | Four-chambered heart (two atria, two ventricles). | Four-chambered heart (two atria, two ventricles). |
| Septum | Incomplete ventricular septum (except in crocodiles, which have a complete septum). | Complete septum separating oxygenated and deoxygenated blood. | Complete septum, ensuring complete separation of blood. |
| Circulation Type | Incomplete double circulation; partial mixing of oxygenated and deoxygenated blood. | Double circulation; no mixing of oxygenated and deoxygenated blood. | Double circulation; complete separation of oxygenated and deoxygenated blood. |
| Efficiency | Moderate efficiency in oxygen delivery due to partial mixing. | Highly efficient; supports high metabolic rate. | Highly efficient; supports high metabolic rate and complex physiological functions. |
| Adaptations | Adapted to ectothermic lifestyle; energy-efficient but less suited for sustained activity. | Adapted to endothermy; supports high oxygen demand for flight. | Adapted to endothermy; supports high energy demands and homeostasis. |
| Aorta | Single systemic aorta that may lead to some mixing of blood. | Right systemic aorta (aortic arch loops to the right). | Left systemic aorta (aortic arch loops to the left). |
| Heartbeat Regulation | Less complex; relies on basic neural and hormonal controls. | Advanced regulation; supports rapid and sustained activity. | Highly advanced regulation for diverse physiological activities. |
Conclusion:
Double circulation is a vital process that ensures the efficient delivery of oxygen and nutrients to all parts of the body. By circulating blood through the heart twice in one complete cycle, the body can maintain a constant supply of oxygenated blood to support cellular functions and remove waste products.