TAXONOMY AND EVOLUTION
Killer whales are in the order Cetacea which includes all dolphins, porpoises, and whales. They belong to the suborder Odontoceti which includes the toothed whales, dophins and porpoises. They belong to the family Delphinidae or the dolphins, and killer whales are the largest of the group. The genus is Orcinus and species is orca. Killer whales had a reputation for being fierce killing machines which is why the Spanish called them "ballena asesina" or the assassin whale (10). They were often seen attacking other whales, sharks, and dolphins. However in Latin, the name orca means "the shape of a barrel or cask" which is due to their shape (1).
Cetaceans roamed the oceans long before recorded history probably up to 5-7 million years ago. It is thought that early dolphins evolved about 55-65 million years ago from now extinct ancient land mammals that ventured back into the sea.
One fossil that closely resembles the killer whale is Ambulocetues natans which was found in Pakistan to have legs but also many characteristics of whales (1). Also many fossils from the Pliocene era are thought to be related to the orca because of their teeth.
Killer whales are mammals because they control their own body temperature, and it remains constant independent of its environment. They also have small hairs to help in sensory, they have mammary glands in which they use to feed their young. They also breathe through lungs using their blowhole to inhale and exhale. They give a live birth and take care of their young.
HABITAT, SOCIAL STRUCTURE AND ACTIVITY CYCLE
Killer whales, also called Orcas, live in all of the world's oceans, establishing a particular preference for the cool or coastal temperate climates although they have been spotted off the coasts of Hawaii, Australia,