Marine Mammals
Whales and dolphins are classified as mammals because they share key mammalian traits, not fish characteristics:
* Live birth: They give birth to live young instead of laying eggs.
* Milk: Females have mammary glands and nurse their offspring.
* Air breathing: They have lungs and must surface to breathe, unlike fish with gills.
* Warm-blooded: They maintain a constant body temperature.
* Hair: All whales and dolphins have hair at some stage of life, even if only a few bristles.
Evolutionary History
Whales and dolphins evolved from land mammals millions of years ago. They adapted to ocean life with streamlined bodies and flippers, but their internal anatomy still reflects their mammalian ancestry.
Despite their aquatic lifestyle, whales and dolphins are fundamentally mammals.