Answer Happy

please help me answer 3 and 4
3. A rib cage is present in the rat and pigeon but missing in the frog. Can this difference be related to the fact that frogs breathe by positive pressure, while birds and mammals breathe by negative pressure? (A frog swallows air and then pushes the air into its lungs; in birds and mammals, the thorax expands first, and then the air is drawn in.) Explain. 4. A diaphragm is present only in mammals (e.g., rat). Of what benefit is this feature to the expansion of lungs in mammals? 5. Air sacs (not shown in Fig. 31.12) are present only in birds. This feature allows air to pass one way through the lungs of a bird and greatly increases the bird's ability to extract oxygen from the air.