Sammakkoeläinten

Sammakkoeläimet, or amphibians, are a class of cold-blooded vertebrates characterized by a life cycle that typically involves an aquatic larval stage followed by a terrestrial or semi-aquatic adult stage. This dual life is reflected in their name, derived from Greek words meaning "double life." Most amphibians undergo metamorphosis, transforming from gill-breathing, finned larvae (like tadpoles) into air-breathing adults with lungs and limbs.

Key features of amphibians include their moist, permeable skin, which plays a crucial role in respiration and water balance, often allowing them to absorb oxygen directly through their skin. This skin is typically smooth and lacks scales, feathers, or fur, though some species may have a leathery texture. They are ectothermic, meaning they rely on external sources of heat to regulate their body temperature.

The class Amphibia is divided into three main extant orders: Anura, which includes frogs and toads, distinguished by their lack of tails in adulthood and powerful hind limbs for jumping; Caudata, comprising salamanders and newts, which retain a tail throughout their lives and typically have a slender body with four limbs; and Gymnophiona, the caecilians, which are limbless, worm-like amphibians that often live underground or in water.

Amphibians inhabit a wide range of environments, from tropical rainforests to temperate woodlands, and are found on every continent except Antarctica. Their dependence on moist environments and their permeable skin make them particularly vulnerable to habitat loss, pollution, and climate change, leading to significant population declines in many species. They play important roles in ecosystems as both predators and prey.