Whale

Whales are an order of marine mammals, the Cetaceans.

Living whales are seperated into the toothed whales (which includes dolphins, porpoises, narwhals, beaked whales and sperm whales) and the whalebone whales; those (mostly very large) cetaceans which have teeth replaced by baleen (whalebone) to filter small prey from the water, which are what people generally think of when the word whale is used. The whalebone whales include the rorquals - the blue whale, fin whale, sei whale, Bryde's whale, minke whale, grey whale; and the various right whales.

Although whales are famed for the massive size reached by some species, such as the blue whale (the largest animal to ever live), others are relatively small like the pygmy right whale which grows to about 20 feet . Though whales have many traits in common with fish (including fins and tails) they are in fact mammals and accordingly breath air and lactate. Whales have a number of remarkable adaptations including:

• they decide when to breathe, rather than breathing unconsciously

• they sleep 8 hours a day, yet need to be conscious to breathe

• they can communicate with each other by making remarkably loud noises

• these extraordinary noises can travel for miles under water

• the females nurse their calves while swimming underwater

• the males have a unique cooling system for their internal reproductive organs

• some have two blow-holes, but others only have one

• the blow-holes pass air above water, yet resist intense pressure underwater

• they have massive brains, much larger than the brains of other mammals

Evolution and taxonomy

The question of how whales and their relatives could have evolved from terrestrial mammals has taxed evolutionary biologists since Darwin's suggestion that they may have evolved from ancient bears. In more recent times molecular and fossil evidence has combined to suggest that modern whales and their relatives arose from ancient artiodactyls (even-toed ungulates) with the closest living relative of all whales being hippos. This kinship has been termed the whippo hypothesis. Evolutionary biologists estimate the last ancestor of whales and hippos lived about 25 million years ago , which is contrast with the young earth creationist position that that whales were created about 4000 years ago when God created the earth. Other creationists are not convinced that the available fossil evidence supports the evolutionary view but make no reference to the corroborating molecular evidence.