Whales are marine mammals from the cetacean infraorder, not related to dolphins or harbor porpoises. Killer whales and grinds have the word whale in their unofficial names (killer whale), although by strict classification they are dolphins. In the outdated classification, whales meant smooth whales (lat. Balaenidae). In olden times, the word whale was sometimes used to mean the leviathan.
Origin and species
Cetaceans, in particular whales, are the largest among animals: a blue whale (blue whale) in an adult state reaches an average body length of m (the largest up to m) and masses - all cetaceans, including whales, dolphins and porpoises, are descendants of land mammals of the artiodactyl order. According to molecular genetic data, cetaceans are an infraorder of artiodactyls. Moreover, according to these data, hippos are among the closest living relatives of whales; they came from a common ancestor who lived about a million years ago. The whales switched to an aquatic lifestyle some millions of years ago. Cetaceans are divided into three parrot orders:
Baleen whales (Mysticeti), characterized by a mustache, a filter-like structure located on the upper jaw, consisting mainly of keratin. The whisker is used to filter plankton from water, filtering large quantities of water with the comb structure of the mouth. Whiskers are the largest suborder of whales.
Toothed whales (Odontoceti) possess teeth and prey on large fish and squid. This is their main source of food. A remarkable ability of this group is the ability to sense their environment with echolocation. Toothed include dolphins and porpoises.
Ancient whales (Archaeoceti) are currently a completely extinct group.
Like all mammals, whales breathe air with the help of the lungs, are warm-blooded, feed their young with milk from the mammary glands and have a hairline (albeit quite reduced).
The body is fusiform, like a streamlined body of fish. The fins, sometimes also called fins, have a lobe-like appearance. At the end of the tail there is a fin of two horizontal blades, playing the role of mover and stabilizer, providing forward movement due to wave-like movements in the vertical plane (unlike, for example, fish and aquatic reptiles, in which the plane of movement of the rowing tail is horizontal).
Different protective devices have been developed for different groups of cetaceans to protect the skin from the harmful effects of the ultraviolet rays of the sun: for example, a blue whale is able to increase the content of ultraviolet absorbing pigments in the skin (sunbathe); others, like a sperm whale, trigger a special stress response, as a defense against oxygen radicals; others, like finwal, use both methods. In cold water, whales maintain their body temperature thanks to a thick layer of fat under their skin. This layer protects the internal organs from hypothermia.
Due to the fact that whales, like dolphins, need to occasionally rise to the surface for breathing, only half of their brain can sleep at a certain point in time.
Whale fishing has been going on since the end of the first millennium AD. The purpose of whaling was primarily the extraction of blubber, which served as fuel and valuable industrial raw materials. The extraction of whales for the sake of meat (whale) began to play a significant role only in the second half of the 20th century (whale was used, in particular, for making sausages). A whalebone was also valuable, vitamin A was obtained from the liver of whales, hormones, in particular insulin, were obtained from glands and the brain
Intensive fishing of whales eventually led to a strong reduction in their numbers, and in 1931 the first international steps were taken to limit its size. In 1982, a moratorium on prey for cetaceans was introduced. Currently, several countries continue to limit the fishing of whales, including for scientific purposes and to meet the needs of indigenous peoples.