Since historical time’s organisms gradually undergo change in all body aspects for example body size, shape, complexity of organs and slight changes in genetic material. The changes are minor in a generation; accumulate with the continuity of generations with the overall differences producing major changes. In most cases a group of organisms arise from a common ancestor for example whales, dolphins and porpoises evolved from mammals that lived on land for instance pakicetids and mesonychids.
Whales are also thought to have a common ancestor with hippopotamus, deer and camels. Whale ancestors were terrestrial which as a result of modification in the body parts and organs gave rise to the present day whales. There are many theories that explain the evolution of whales and the most embraced is that of whales evolving from small aquatic animals. The rule of natural selection by Charles Darwin dictates that only the fit organisms survive. This rule has applied to the evolution of whales since those that were unable to cope with competition became extinct.
Most of the ancestors of whales were obtained through fossil study (paleontological evidence) of both terrestrial and aquatic organisms’ remnants excavated from Australia and Pakistan. Some of the examples of whale ancestors are sinonyx, pakicetids, ambulocetids, rhodocetids, basilosaurus, dorudon, squalodon, mammalodon colliveri, janjucetus hunderi and Harrison’s whale. Statement on whales Whales are the largest living mammals that inhabit aquatic environment. Whales can dive to depths of about 3000 meters and have to go back to the surface to breath.
Like most terrestrial mammals whales give birth, suckle and nurse their young ones for around six months. They do not have skin glands, tear glands and olfactory senses. They receive signals through vibrations to the periodic and auditory bullae formed by fusion of skull bones. The blue whale; one of the whale species is the largest creatures that has ever lived on earth. The whale is subdivided into several species namely; sperm whale, blue whale (mentioned above), orcas (killer whales), and pilot whales.
Some of these whale species have become extinct through natural selection as postulated by Charles Darwin in his theory “the origin of species by means of natural selection”. The blue whale is in the sub- order baleen whale and has long slender body shaded blue at some parts of the body. They feed on krill and only hunt in areas with concentration of krill. They mostly mate during autumn. Blue whales give birth to young whales in water weighing about two tones. The blue whales suckle their young ones till they are six months old.
These whales are sexually mature at the age of around ten years. They are known to attain the age of about eighty years and their only predator is the orca or the killer whale. The population of whales has been decreasing in the recent years because of large scale whale hunting. Blue whales communicate to other whales especially during courtship, locating prey, maintenance of individual territory and maintenance of social organization by making some sounds about 165 decibels.
Courtney from Study Moose
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