What is incorrect about the circulatory system of aves ?

Question

Accepted Answer

The question asks about what is incorrect regarding the circulatory system of aves (birds). The correct answer is Option 2: "Well developed renal portal system."

1. **Explanation for Option 2:**
   - In birds, the renal portal system is not as well-developed as it is in some other vertebrates. While birds do have a renal portal system, it is not as prominent or functionally significant as it is in reptiles or amphibians. The renal portal system in birds is relatively reduced, and its role in circulation is not as critical. Therefore, stating that birds have a "well developed renal portal system" is incorrect, making Option 2 the correct choice for what is incorrect about the circulatory system of aves.

2. **Explanation for why the other options are incorrect:**

- **Option 1: Heart is four chambered.**
     - This statement is correct. Birds have a four-chambered heart, consisting of two atria and two ventricles, which allows for complete separation of oxygenated and deoxygenated blood. This is a characteristic feature of the avian circulatory system and is essential for their high metabolic demands.

- **Option 3: Sinus venosus and truncus arteriosus are lacking.**
     - This statement is also correct. In birds, the sinus venosus is reduced and incorporated into the wall of the right atrium, and the truncus arteriosus is not present as a separate structure. These features are consistent with the advanced circulatory system of birds, which supports efficient oxygen transport.

- **Option 4: R. B. Cs are nucleated.**
     - This statement is correct as well. Unlike mammals, birds have nucleated red blood cells (RBCs). This is a distinctive feature of avian blood cells and is accurate in describing the circulatory system of birds.

In conclusion, Option 2 is the correct answer because it inaccurately describes the renal portal system in birds as "well developed," whereas the other options accurately describe features of the avian circulatory system.