Overview:
Tadpoles are the larval stage of frogs and other amphibians. During this stage of their life cycle, tadpoles undergo significant physical changes as they transform into adult frogs. One of the most important changes that occur during this process is the development of gills, which allow tadpoles to respire or breathe underwater.

Gills for Respiration:
- Tadpoles respire through their gills, which are specialized organs that allow for gas exchange in water.
- Gills are thin, feathery structures located on either side of the tadpole's head, behind the eyes.
- These gills are protected by a bony structure called the operculum.
- As water passes over the gills, oxygen from the water diffuses into the bloodstream of the tadpole, while carbon dioxide is released into the water.

Gill Structure and Function:
- The gills of tadpoles are composed of a network of tiny blood vessels, called capillaries, that are surrounded by thin, moist gill filaments.
- These filaments increase the surface area available for gas exchange, allowing for efficient respiration.
- Tadpoles continuously pump water over their gills by opening and closing their mouths, which helps to maintain a constant flow of oxygenated water.

Other Respiratory Adaptations:
- In addition to gills, tadpoles also have a small amount of respiratory exchange occurring across their skin.
- However, gills are the primary respiratory organs for tadpoles, especially in aquatic environments.
- As tadpoles grow and develop into adult frogs, they undergo a process called metamorphosis, during which their gills are replaced by lungs.

Conclusion:
In summary, tadpoles respire through their gills, which are specialized organs for extracting oxygen from water and releasing carbon dioxide. This adaptation allows them to efficiently respire underwater. As tadpoles undergo metamorphosis and transform into adult frogs, their gills are replaced by lungs, enabling them to respire in a terrestrial environment.