Large surface area, permeable to respiratory gases, moist, has thin walls, and has a blood network to transport gases

Insects = tracheal system, fish = gills, amphibians = lungs and skin, and humans = lungs

Trachea and tracheol; carrying air, chitin rings on the trachea; strengthens the structure of the trachea, fine tracheal tube and has a spiracle (valve)

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The lamellae of the gill filaments have a thin wall and are supplied with many blood capillaries

The skin is moist which easy for the gas to dissolve. Under the skin, there is a network of blood capillaries to transport respiratory gases

The surface of the frog's lungs is folded to increase the surface area, the walls of the lungs are moist, thin and have a large network of blood capillaries beneath them to transport gases

There are many alveoli that increase the surface area, the walls of the alveoli are moist and one-cell thick, and are surrounded by a network of blood capillaries to transport gas

Is the respiratory surface that enables gaseous exchange to occur between respiring organism cells and their outer environment