Guard cell movement furnishes an example of

Due to the presence of which structure is the pulmonary ventilation system in humans better developed than in reptiles and birds?

Explain the mechanism of breathing with neat labelled sketches.

Explain the mechanism of expiration.

The lungs do not collapse during breathing and some air always remains in the lungs which can never be expelled because:

Select the correct process that occurs during inspiration (inhalation):
$(a)$ Contraction of the diaphragm
$(b)$ Contraction of external intercostal muscles
$(c)$ Decrease in pulmonary volume
$(d)$ Increase in intra-pulmonary pressure