Life Processes in Animals — Science STD 7 — Question

The process of breathing happens in two steps inhalation (breathing in) and exhalation (breathing out).
(i) When we inhale air, the diaphragm moves downwards and the chest cavity expands. This makes space for the lungs to fill with air. Air rushes in and fills the tiny air sacs in the lungs called alveoli.
(ii) When we exhale, the diaphragm moves upwards and the chest cavity becomes smaller. This pushes out the air containing carbon dioxide and water vapour from the lungs.