Carbon dioxide, more soluble in water than oxygen, is mainly carried in its dissolved form in the blood.

Haemoglobin, a respiratory pigment in red blood cells, has a high affinity for oxygen, facilitating its transport from the lungs to oxygen-deficient tissues.

Diffusion pressure alone becomes insufficient for oxygen delivery to all body parts in large animals.

Gaseous exchange occurs across the surface of stems, roots, and leaves, ensuring efficient gas exchange for photosynthesis and other plant processes.

Guard cells regulate the opening and closing of stomatal pores; they swell with water, causing the pore to open, and shrink to close it, controlling gas exchange and water loss.