They can locomote on the land and they have lungs which help them to respire on land and gills on water.....

Characteristics Helping Amphibians to Live on Land

1. Moist Skin:
Amphibians have evolved several characteristics that enable them to survive on land, despite their aquatic origins. One of the key features that aid their terrestrial existence is their moist skin. The moist skin of amphibians serves multiple purposes and plays a crucial role in their survival.

- Respiration: Amphibians have a thin, permeable skin that allows for gas exchange with the surrounding environment. While in water, oxygen is absorbed through the skin, and carbon dioxide is expelled. On land, the skin must remain moist for this process to continue, as oxygen dissolves in water more easily than in dry air. The moist skin also helps prevent dehydration, which is a constant threat in terrestrial habitats.

- Thermoregulation: Amphibians are ectothermic, meaning their body temperature is regulated by the external environment. Their moist skin facilitates heat exchange with the surroundings, allowing them to cool down by evaporation when it's hot and absorb heat when it's cool. This adaptation helps them maintain an optimal body temperature for various physiological processes.

- Protection: The moist skin of amphibians also acts as a protective barrier against harmful environmental factors such as UV radiation, parasites, and pathogens. Mucus secreted by the skin forms an additional layer of defense against pathogens and helps prevent desiccation.

2. Lungs and Gills:
While amphibians primarily respire through their skin, they have also developed specialized respiratory organs to aid their survival on land.

- Lungs: Amphibians possess lungs that allow them to breathe air. These lungs are relatively simple compared to those of reptiles, birds, or mammals. However, they provide an additional means of respiration when the skin alone is insufficient, such as during periods of drought or when the oxygen demand is high. Some amphibians, like frogs and toads, have lungs throughout their lives, while others, like salamanders, may lose their gills and rely solely on lungs as they mature.

- Gills: During their aquatic larval stage, many amphibians possess gills for respiration. These gills are highly efficient in extracting oxygen from water. However, as they transition to a terrestrial lifestyle, these gills are usually lost or modified into more specialized structures. This adaptation allows amphibians to respire primarily through their moist skin and lungs, while still retaining some gill-like structures to aid in respiration in water or in humid environments.

In conclusion, the moist skin of amphibians plays a vital role in respiration, thermoregulation, and protection, enabling their survival on land. Additionally, the presence of both lungs and gills allows them to respire in varying environments, further enhancing their adaptability to terrestrial life. These evolutionary characteristics have allowed amphibians to successfully colonize diverse habitats across the globe.