CBSE Class 10 Science 2020 · Paper 31/1/1 · Question 27(a)

(a) Aquatic organisms take in the oxygen dissolved in water, while terrestrial organisms take in oxygen from the air. The amount of dissolved oxygen in water is much lower than the amount of oxygen in air, so aquatic organisms have to breathe much faster than terrestrial organisms to obtain enough oxygen. (b) The diagram of the human respiratory system shows the nasal passage leading to the pharynx and larynx and into the trachea, which divides into two bronchi, one to each lung; the bronchi branch into bronchioles, which end in alveolar sacs; the dome-shaped diaphragm lies below the lungs. The labels are pharynx, trachea, lungs, diaphragm and alveolar sac.