- This method involves the presence of lungs as respiratory surfaces, where the exchange of gases (oxygen and carbon dioxide) takes place. Lungs are highly folded structures, increasing their surface area for efficient gas exchange. Mammals, birds, and some reptiles use pulmonary respiration.
2. Cutaneous respiration:
- In cutaneous respiration, the skin is the primary respiratory organ. The skin is moist, thin, and richly supplied with blood vessels, allowing the diffusion of gases between the body fluids and the external environment. Earthworms, amphibians (such as frogs and salamanders), and some aquatic organisms use cutaneous respiration.
3. Tracheal respiration:
- Tracheal respiration is found in insects and some other invertebrates. A network of branching air tubes called tracheae is present throughout their body, supplying oxygen directly to the tissues and removing carbon dioxide.