Amphibians are vertebrates of the taxonomic class Amphibia including animals such as frogs and toads (order Anura), salamanders (order Caudata), and caecilians (order Gymnophiona). Thought of as cold-blooded, amphibians are ectotherms, meaning they are unable to regulate their own body temperature independently of the temperature of their surroundings. Amphibians are generally small with thin skin permeable to air and water. With few exceptions, amphibians do not actively care for their young. In general, amphibian reproduction strategy consists of egg-laying and external fertilization of a large number of eggs in a moist or fully aquatic environment. Fertilized eggs develop into amphibian larvae that live part of their lives dependent on an aquatic environment requiring gills and specialized feeding habits. Following a pattern of development unique to amphibians, amphibian larvae undergo marked changes and metamorphose into a terrestrial form that lives on land. Typically, this metamorphosis is demonstrated by loss of gills, changes in overall appearance, and changes in diet.