amphibian

An amphibian is a member of the class Amphibia, a diverse group of cold-blooded vertebrates that typically have a dual life stage, living part of their life in water and part on land. Amphibians include frogs, toads, salamanders, newts, and caecilians. They are characterized by their moist, permeable skin, which plays a vital role in respiration and moisture absorption, and lack scales, unlike many other fish and reptiles.

Amphibians generally undergo metamorphosis, starting life as aquatic larvae with gills and a tail, and transforming into terrestrial or semi-terrestrial adults with lungs and limbs. Their reproductive process is predominantly external, with fertilization occurring outside the female's body, often in water. This reliance on aquatic environments for breeding makes many species sensitive to changes in water quality and habitat conditions.

These animals are found on every continent except Antarctica, with the greatest diversity in tropical regions. Amphibians serve important ecological roles, including controlling insect populations and acting as prey for a variety of predators. They are also considered bioindicators because of their sensitive skin and life cycle, which make them early warning signs of environmental health.

Amphibian populations are currently facing global declines, primarily due to habitat destruction, pollution, climate change, and emerging diseases such as chytridiomycosis. Conservation efforts focus on habitat preservation, environmental regulation, and disease management to protect these vulnerable species.

Overall, amphibians represent a critical link in the evolution of vertebrates and offer valuable insights into developmental biology, ecology, and environmental health.