1. Mammals: Whales are mammals, meaning they share certain characteristics with other mammals like humans, dogs, and bats:
* Warm-blooded: They maintain a constant internal body temperature.
* Breathe air: They have lungs and need to come to the surface to breathe.
* Give birth to live young: They don't lay eggs.
* Nurse their young: They produce milk to feed their offspring.
* Have hair (at least some): While most adult whales have very little hair, they have hair follicles and some species retain hair, especially young whales.
2. Aquatic Lifestyle: Whales are adapted for life in the water:
* Streamlined bodies: Their bodies are shaped to reduce drag in the water.
* Flippers and fluke: They have modified limbs for swimming.
* Blowhole: They have a special opening on top of their head for breathing.
3. Evolutionary History: Whales evolved from land mammals over millions of years. Their ancestors were four-legged creatures that gradually adapted to a marine environment.
4. Diverse Group: Whales are a diverse group, with a wide range of sizes, shapes, and behaviors. They are divided into two suborders:
* Odontocetes: Toothed whales, like dolphins, porpoises, and orcas.
* Mysticetes: Baleen whales, like humpback whales, blue whales, and gray whales.
In short, a whale is a mammal that lives in the water, breathes air, and has a streamlined body adapted for swimming. They are a diverse group with a fascinating evolutionary history.