Of all the classes of animal life, mammals are considered the most modern and probably the most popular class. Dogs and cats are mammals, squirrels and rabbits in our backyards are mammals, as well. Horses, sheep, baboons, giraffes and elephants are mammals. Moreover, we humans are mammals too.
Mammals vary greatly in size. The smallest mammal is the shrew with a body that is little more than 2 inches long and weighs less than a few insects. On the contrary,The largest mammal is the blue whale, which sometimes can be up to 100 meters long and weigh up to 130 tons. Although mammals have a different appearance in the form. Most of them go on all fours, but not all do. Some mammals fly. Dolphins and whales lost their hind legs and have now taken as the shapes of fish and spend their entire lives in the ocean.
What is a mammal? Mammals are vertebrates - animals with a backbone are. All mammals have lungs and breathe air, and allof them are warm-blooded mammals and birds have a common characteristic (they are able to maintain a constant body temperature regardless of outside temperature.) - the organization of four chambers of the heart, the blood flowing efficiently to all parts of the body. All mammals, except to put the two types, the eggs give birth to live young and provide protection and care for them, before and after birth. Mammals are the only animals that real hair and the ability to produce milk to possess. InIn fact, the "mammal", a word from the Latin word "Mama", the "breast" means.
Mammals have other properties that are not so obvious. A heart and lungs of mammals are called separately from the stomach through a wall of the diaphragm muscle. A mammal has a single bone of the lower jaw on each side. Mammals have adapted to different types of teeth for various applications. And most of all mammalian brains are much more developed than the brains of other animals.
In the fightto survive, have warm blood, improved methods of care for youth and high intelligence, since all mammals great advantages over the centuries. In fact, many scientists mammals such as the dominant animal in the world.
But the mammals did not begin immediately as mammals. Strange as it may seem, they went out of reptiles. Started a branch of the Mesozoic reptiles coats the hair to grow instead of arms and turned slowly warm-blooded animals. Some of them began to hold the eggsto put in their bodies, instead of eggs. The earliest mammals were probably very small and shy creatures, like mice and rats today. They were night and hide during the day for protection. If the conditions of the Earth gradually changed, the dinosaurs could not adapt to this dramatic change, so that their number was smaller. When he died, the more adaptable mammals arose later in the Miocene.
Between 3500 and 5000 species of mammals live in the world today andOther varieties of them. Many of these animals for their descent, their ancestors, who adapted and survived through the Ice Age. Mammals now in a bewildering variety of sizes and shapes have evolved, classified by scientists according to body structure and relationships. Throughout the reign of mammals, there are now 18 different groups or orders.
