(a) Why is there a difference in the rate of breathing between aquatic organisms and terrestrial organisms? Explain. (b) Draw a diagram of the human respiratory system and label it – the pharynx, trachea, lungs, diaphragm and alveolar sac on it.

Aquatic organisms like fish extract oxygen from water, which contains much less dissolved oxygen than air. As a result, they need to breathe faster to obtain sufficient oxygen to meet their energy needs. Terrestrial organisms, on the other hand, get oxygen from air, which has a higher concentration of oxygen, so their breathing rate is comparatively slower.

Label diagram of the human respiratory system