A whale is a mammal, not an amphibian. While both mammals and amphibians are part of the animal kingdom, they have distinct characteristics that set them apart.
Mammals are warm-blooded vertebrates that have hair or fur and most give live birth. They also possess mammary glands, which produce milk to nourish their young. Whales, belonging to the order Cetacea, exhibit these traits: they are warm-blooded, breathe air through lungs, and nurse their calves with milk.
On the other hand, amphibians, such as frogs and salamanders, typically have a life cycle that includes both aquatic and terrestrial phases. They usually lay eggs in water, and their skin is generally moist and permeable to water, which is essential for their respiration and reproduction.
In summary, whales are classified as mammals due to their unique physiological features, while amphibians represent a different class of animals with their own set of characteristics.