The gases are to dissolve and diffuse through.
The exchange surfaces are moist.
Surfactant
Gas exchange surfaces like the alveoli need to be moist because gases, such as oxygen and carbon dioxide, dissolve in water. The thin layer of moisture in the alveoli allows for efficient exchange of gases between the air in the lungs and the bloodstream. This ensures that oxygen can be absorbed into the blood and carbon dioxide can be released from the blood.
diffusion
Amphibians.. because they exchange gas partly through their skin, so gases must be able to move in and out - Their skin's got to be permeable and moist.
they are connected to a densed network of blood vessels which keeps the oxygen moist
Frogs uses respiratory surfaces which totals to three to exchange gases on its surroundings. The three respiratory surfaces are the skin, its lungs, and the lining of their mouth.
Respiratory surface is the surface where respiratory gas exchange in an animal. Ex-lungs
Gas exchange takes place at a respiratory surface-a boundary between the external environment and the interior of the organism. For unicellular organisms the respiratory surface is governed by Fick's law, which determines that respiratory surfaces must have:a large surface areaa thin permeable surfacea moist exchange surface.
The RS, or respiratory system, is kept moist primarily through the secretion of mucus by goblet cells and mucous glands lining the airways. This mucus traps dust, pathogens, and other particles, helping to maintain a moist environment that is essential for effective gas exchange. Additionally, the moisture in the air we breathe contributes to the hydration of the respiratory surfaces. Keeping the airways moist is crucial for maintaining healthy respiratory function and preventing irritation.
In any living organism that needs to breath, the only thing consistently required for life is the presence of moist membranes. The movement of oxygen and carbon dioxide across the membranes between the environment and the respiratory surface occurs by diffusion. Respiratory surfaces are generally thin and, since living animal cells must be wet in order to maintain their plasma membranes, these respiratory surfaces must be moist.
Jellyfish are, compared to mollusks, arthropods and vertebrates, very simple organisms. Jellyfish did not evolve a respiratory or an excretory system, as they can perform gas exchange at their outer surfaces.