What is an amphibian?

What is an amphibian?

• A. A cold-blooded vertebrate that begins life in water with gills and metamorphosis to life on land.
• B. A warm-blooded vertebrate that gives birth to live young.
• C. A mammal with hair and mammary glands.
• D. A bird with feathers.

Answer: (A)

Amphibians are vertebrates that typically begin life in water, laying eggs that hatch into gilled larval forms, and many species then undergo metamorphosis to become air-dwelling adults. They are cold-blooded, meaning their body temperature varies with the environment, and their skin is usually moist and permeable, which helps with respiration but ties them to damp habitats. Frogs, toads, and salamanders are common examples. This combination of starting life in water and undergoing metamorphosis sets amphibians apart from warm-blooded mammals, which give birth to live young and have hair and mammary glands, and from birds, which have feathers.