Anfíbios

Anfíbios are a class of cold-blooded vertebrate animals that typically spend part of their lives in water and part on land. The name "amphibian" comes from the Greek word amphibios, meaning "dual life." This dual existence is a defining characteristic, as most amphibians undergo a metamorphosis from an aquatic larval stage to a terrestrial or semi-terrestrial adult form.

The life cycle of many amphibians begins as an egg, usually laid in water or moist environments. These eggs hatch into larvae, such as tadpoles in frogs and toads, which are aquatic and breathe through gills. As they mature, they undergo metamorphosis, developing lungs, limbs, and often losing their gills. This transformation allows them to survive and reproduce outside of water.

Amphibians have smooth, moist, and permeable skin, which plays a crucial role in respiration, allowing them to absorb oxygen directly through their skin. This skin also requires moisture to prevent drying out, hence their reliance on damp habitats or aquatic environments. Their diet generally consists of insects, worms, and other small invertebrates.

The class Amphibia is divided into three main orders: Anura (frogs and toads), Urodela or Caudata (salamanders and newts), and Gymnophiona or Apoda (caecilians). Frogs and toads are characterized by their absence of tails in adulthood and their strong hind legs for jumping. Salamanders and newts retain their tails throughout their lives and typically have a more elongated body shape. Caecilians are limbless, serpentine amphibians that often live underground or in water.

Amphibians are important indicators of environmental health due to their permeable skin and reliance on specific habitats. Declines in amphibian populations worldwide are often attributed to habitat loss, pollution, climate change, and emerging infectious diseases.