Among mammals, the efficiency of ventilation of lungs as compared to reptiles and birds is better developed by the presence of

Options

A. Ribs `&` costal muscles
B. Only ribs
C. Only costal muscles
D. Diaphragm

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks about the reason for the better efficiency of lung ventilation in mammals compared to reptiles and birds.

2. **Identifying Key Features of Mammalian Respiration:**
- Mammals have a more complex respiratory system than reptiles and birds.
- They possess lungs, ribs, and muscles that assist in the breathing process.

3. **Role of Ribs and Intercostal Muscles:**
- Mammals have ribs that protect the lungs and aid in the expansion and contraction of the thoracic cavity.
- Intercostal muscles (both internal and external) are present between the ribs and help in increasing the volume of the thoracic cavity during inhalation.

4. **Importance of the Diaphragm:**
- The diaphragm is a dome-shaped muscle located below the lungs.
- It plays a crucial role in respiration by contracting and flattening during inhalation, which increases the volume of the thoracic cavity and allows air to flow into the lungs.

5. **Comparing to Reptiles and Birds:**
- While reptiles and birds have their own adaptations for breathing, they do not have the same level of muscular control and structural complexity as mammals.
- This makes mammalian ventilation more efficient.

6. **Conclusion:**
- The efficiency of lung ventilation in mammals is better developed due to the presence of ribs, costal muscles, and the diaphragm.

**Final Answer:**
The efficiency of ventilation of lungs in mammals, as compared to reptiles and birds, is better developed by the presence of **ribs and costal muscles**.

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