Even in prehistoric times, the Earth was inhabited by giant creatures that were much larger than all living animals. They were ancient whales. Today, the blue whale is the largest animal on the Globe. It is about thirty meters long and weighs about one hundred and twenty-five tons. And here is what is remarkable: about a third of the length of this animal is occupied by its head.
But perhaps the most interesting thing about the whale is not its size, but the fact that it is a mammal, not a fish. Like other mammals that live in water (such as dolphins and sea lions), whales are descended from ancestors that once lived on land. This proves the structure of their bodies. The fins of whales resemble paws with five fingers, covered with skin and muscle tissue. They are somewhat similar to oars. Some whales even retained underdeveloped bones of the hind limbs.
Since whales are mammals, their young, as well as the young of other animals of this class, are fed with mother’s milk. They are not bred from eggs like fish, but are born alive and remain with their mother for some time after birth.
Whales don’t have gills, they breathe with their lungs. Their tail fin is positioned horizontally and helps them easily rise to the surface of the water when they need to breathe. The internal organs of whales, their skeleton, circulatory system and brain are very different from fish.
In the process of adapting whales to life in the water, their body has suffered serious changes. For example, the formation of a fat layer occurred. Mammals are warm – blooded animals, and constant body temperature is very important for them. The fat layer allows the whales to keep warm and not get supercooled. In large whales, the thickness of the fat layer can reach 35-55 centimeters.
At the top of the whale’s head are two holes through which the animal breathes on the surface of the water. Under water, these” nostrils ” are closed by small valves, and air access through the respiratory channels is stopped, which eliminates the risk of water entering the lungs, so whales can stay under water for up to 45 minutes.