Orca | Killer Whale - BBC Documentary
Orca | Killer Whale
Mammals are characterized by the following features:
Mammals breathe air with lungs.
Mammals are "warm-blooded": they maintain a constant, high body temperature independent of their surroundings.
As a rule, mammals bear live young. (Two primitive mammals are exceptions to this rule: the duckbilled platypus and the spiny anteater/echidna both lay eggs).
Mammals nurse their young with milk.
Mammals have hair, at least at some stage in their development. A whale's smooth skin is an adaptation for swimming. A newborn calf often has a few sparse hairs around the rostrum that are lost within the first days of life.
