Amphibious (amphibians) are cold blooded vertebrate animals who live in an adult state mainly on the land, however their reproduction and initial development takes place in water (damp places, reservoirs). Amphibians – the most primitive vertebrate animals occupying an intermediate step between water and land life forms.
Instruction
1. In translation from Greek the word "amphibians" means "dvoyakozhivushchy". The term "amphibians" is usually used in the scientific environment, and in usual life of these beings call Amphibia. It also is clear: most of them perfectly feel both on the earth, and in water. Frogs, toads, tritons, salamanders and their tadpoles treat representatives of this simple class of animals. Now on Earth there are more than 4500 species of various amphibians. In turn, Amphibia are divided into three groups which are accurately differentiated among themselves. It is curious that representatives of one group are almost not similar to "neighbors" that leads to some doubts concerning their relationship.
2. The most numerous group of Amphibia – tailless amphibians. They still sometimes are called the jumping amphibians. This group of animals contains more than 75% of all species of Amphibia. Frogs and toads treat them. The name of this group speaks for itself: these animals have no tail and move only by means of jumps. The second, less numerous, the group of Amphibia received the name of amphibians having a tail. His representatives the appearance remind lizards, but with the frog head and damp, as at frogs, skin. Representatives of this group in the course of evolution kept the tail. Tritons and salamanders treat them.
3. The smallest and the least studied group of amphibious animals are legless amphibians. In appearance it is very strange creations which do not have not only a tail, but also all the extremities. Chervyag (melkozuby chervyaga, a raznozuby chervyaga, etc.) and rybozme concern them. This group includes only 184 species of animals and is known for the existence in the early Jurassic Period. These unique creations meet not so often as it can seem. An area of their distribution – tropics and subtropics of Southeast Asia, Latin America and Africa. Among legless amphibians there are types which are completely adapted for water, but these are already isolated cases.
4. The vast majority of all amphibious animals live in places with the increased humidity and alternate the stay in water to periodic sorties on the land. But also such species of Amphibia who carries out the lion's share of the life only on trees meet (for example, wood frogs). As it was told above, amphibians – the most primitive vertebrate animals in the world: they are properly not adapted for dwelling only on the land as the intensity of their metabolism (metabolism) is small. Their way of life completely and entirely depends on external factors: change of environmental conditions plays a fatal role in life of amphibious animals.