Question

(i) Why is respiratory pigment needed in multicellular organisms with large body size?
(ii) Give reasons for the following:
(a) Rings of cartilage are present in the throat.
(b) Lungs always contain a residual volume of air.
(c) The diaphragm flattens and ribs are lifted up when we breathe in.
(d) Walls of alveoli contain an extensive network of blood vessels.

Answer 1

(i). Respiratory pigments like hemoglobin are needed to transport oxygen efficiently
in multicellular organisms with large body sizes because:
• Simple diffusion is insufficient to meet their oxygen requirements.
• Respiratory pigments bind to oxygen, ensuring its transport to all parts of the body.

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(ii). (a) Rings of cartilage are present in the throat.
Solution: The rings of cartilage in the throat (trachea) keep the airway open and prevent its collapse during breathing.
(b) Lungs always contain a residual volume of air.
Solution: The residual volume of air prevents the lungs from collapsing and allows continuous exchange of gases even during exhalation.
(c) The diaphragm flattens and ribs are lifted up when we breathe in.
Solution: During inhalation:
• The diaphragm contracts and flattens, increasing the chest cavity’s volume.
• The ribs lift up and outward, reducing air pressure in the lungs, causing air to flow in.
(d) Walls of alveoli contain an extensive network of blood vessels.
Solution: The extensive network of blood vessels in alveoli ensures efficient exchange of oxygen and carbon dioxide between the lungs and blood.