Killer Whale ( Orca )
Killer whales inhabit all oceans of the world. They live areas of cold-water including the Pacific Northwest, along northern Norway's coast in the Atlantic, and the higher latitudes of the Southern Ocean.
Killer whales are mammals. They are also a toothed whale belonging to the oceanic dolphin family.
Killer whale first appeared about 11 million years ago.
Morphological & Molecular Evidence
Closest relatives : Dolphin, porpoises
Dolphin and killer whale both have both carry a layer of blubber that keeps them warm. They all have streamlined bodies without any protruding parts, allowing the animals to glide through the water.
Dolphins and porpoises have same basic structure with killer whales.
Whales have vestigial structures that would have been fully functional in their land-living ancestors, including the pelvic girdle, the hind limbs and the finger muscles.
The vestigial pelvis and hind limbs
The hind limbs of whales, were used for steering. But now they don't use them. so they changed during time. They become much smaller and fully enclosed within the skin. They are also invisible from the outside.
Bones and digital muscles
Long time ago, killer whale looked like a big rat. It had four legs, nose and ears. They also had fur, which looks totally different from nowadays killer whales.
As time pass, pakicetus evolved more like a whale. The fur came off and they got smooth and streamlined bodies. They also got web fingers. They started to have lots of teeth like whales.
Embryo of killer whale and dolphin looks similar. It provides evidence for evolution because it tells you that two organisms have same ancestor.