Variety of animals. Materials for the lesson

In biology, all living organisms that existed and exist on our Earth are divided into four huge groups, called kingdoms. They are bacteria, plants, mushrooms and animals. Each kingdom includes a great number of genera and species, consisting of a large number of units. The imagination and huge variety of fauna are amazing. In turn, animals are divided into single-celled and multicellular, invertebrate and vertebrate organisms. And the science involved in their study is called zoology (the section of biology).

Variety of animals: classification

Invertebrates are usually referred to as worms, mollusks, echinoderms, crustaceans, arachnids and insects. These animals (yes, worms are also animals!) Do not have a pronounced spine inside or outside. Sometimes there is a chitinous shell that performs this role. To the vertebrates include fish, amphibians, reptiles, birds, mammals (a man belongs to the last class, because he feeds his cubs with breast milk).

Invertebrates: worms

The diversity of the animal kingdom can be well represented by studying these creatures. This group includes more than 46 thousand species of organisms. Worms move with elastic muscles, bending the body in different directions. They live in the seas, rivers, lakes, marshes, in the earth. A bright, well-known representative is the earthworm. He lives in the soil, helping to loosen and enrich it. This is very important for all kinds of agricultural work. Many of the class of worms are useful. For example, leeches. They are used in medicine. And sea worms serve as a constant food for commercial fish, extracted by fishermen. Without them, some species of fish simply would not have food. However, there are many worms-parasites existing at the expense of other organisms (parasites on them). Because of insufficient compliance with the rules of personal hygiene, such parasites can get inside the human body and live there for years. So now you understand how important it is to observe simple hygienic rules: wash your hands before meals, do not use dirty dishes, do not allow the presence of flies. By the way, worms, settling inside other organisms, release harmful products of their vital activity, gradually poisoning their host. A person becomes nervous, he is irritated by everything, he quickly gets tired and weakens, there is a constant intoxication of the body, and it is already necessary to seriously interfere with doctors removing all this living creature from the human body with special means.

Shellfish

The variety of animal-mollusks is also great. This group has more than 130 thousand species. And they live almost everywhere, even on trees. But most of them live in the world's oceans at various depths. Some of them are hundreds of years old. Molluscs feed on plants, small animals, and organic waste. Almost all of them have protection in the form of a shell (except, for example, squid, which is also a mollusk, but it also has rudimentary shells). People have long been eating mollusks as food. Some representatives of this group are even delicacies.

Echinoderms

They are starfish (1500 species), which got their name due to the presence of rays on the body (many have five, but some even up to 50 pieces). The stars living in the sea differ in size and appearance. A characteristic feature of the starfish is the ability to regenerate (as in lizards). If an animal is torn off a limb, then a new one grows in its place in speed. And from a torn ray, under favorable conditions, a new individual develops. Most sea stars are predators.

Sea urchins (800 species) also belong to the echinoderm. The body of hedgehogs is covered with needles of various sizes. And the length of the shoots can reach up to 30 centimeters. Hedgehogs move with needles. And among them there are very poisonous, dangerous for other animals.

Crustaceans

The body of these animals consists of armored segments: the head, chest and abdomen. The limbs, located on the abdomen and chest, allow the crayfish to move along the surface. Their eyes consist of many small eyes, and on the head there are several pairs of jaws.

Arachnids and insects

The diversity of animals living on Earth is well represented by these groups, of which there are more than 27 thousand species. These two groups are related. Only insects have six legs, and spiders have eight legs. Still all insects have wings, even if in embryo. Spiders do not have wings. Also, the structure of the body varies: insects have a head, chest and abdomen, and spiders have a cephalothorax and abdomen.

Vertebrate animals

The variety of animals living on our planet is easy to imagine by studying a detachment of vertebrates. This is fish covered with scales. Their great variety of species, among which are very ancient, inhabiting the waters of the ocean from time immemorial (sharks, brush-fish). This is the amphibians, and reptiles, and birds, and mammals that inhabit the surrounding world. The variety of animals is so great that even an experienced zoologist will not give an exact answer to the question of how many species of animals exist in nature. Because there is no definitive answer: new ones are constantly opening up, some existing species disappear. A cycle of nature is taking place, including an endless variety of animals (see photo above).