What mechanism do amphibians use to breathe through their skin?

Amphibians utilize diffusion as the primary mechanism for gas exchange through their skin. This process occurs because amphibian skin is highly permeable and lacks a thick outer layer, which allows oxygen from the environment to move directly into their bloodstream while carbon dioxide diffuses out to the exterior.

The efficiency of diffusion for respiration in amphibians is enhanced by their moist skin, which facilitates the movement of gases. The concentration gradient drives this process: oxygen diffuses from an area of higher concentration in the external environment to an area of lower concentration within the amphibian's body, while carbon dioxide moves in the opposite direction.

This method of breathing through the skin is particularly crucial for amphibians, especially when they are in aquatic environments or during periods when their lungs might not be fully functional, such as in larval stages. Hence, the choice of diffusion accurately describes the physiological process amphibians rely upon for skin respiration.