Invertebrates - many representatives of fauna without a backbone.This category includes protozoa (single-celled), lower worms, sponges, arthropods, molluscs, echinoderms and others.A total of sixteen types of this group.
Separation of wildlife on vertebrates and invertebrates Lamarck realized in 1801.Among vertebrates known about forty five thousand species.Known invertebrates present in an amount of 1 million 260 thousand species.At the same time the simplest - about twenty-five thousand, sponges - about five lower worms - about twenty, mollusks - more than a hundred, arthropods - about seventy-nine thousand species.
The largest number of insect species are represented.They were about a million.This aquatic insects belong to many orders.It should be noted that some of them are present in the water only during the larval period.While there are other life.Coelenterates animals, there are about nine thousand species.It should be noted that the existing types in the nature much more than it is known.In addition, each year is determined by a few thousand new ones.
Invertebrate animals inhabit the soil, oceans, seas, rivers, lakes, ponds.Many of the representatives are parasites.At the same time, they are parasites and beasts, and plants.
role of invertebrates in nature is quite large.Solids representatives who lived in earlier geological periods, become elements of rock, and in some cases - the bulk of them.For example, skeletons of invertebrate animals, extinct, almost completely make up limestone.
multifarious importance of this group and for the individual.For example, many invertebrates, as well as their waste products, used for cooking food for humans (honey, for example).Many representatives used to feed commercial fish, animals, birds.Pearls, shells of mollusks, beeswax, and many other waste products of the representatives of different groups of invertebrates large economic and technical value.Often they are used in pest control.Invertebrates are predators and parasites, to destroy them.This method refers to the biological methods of pest control.Geologists in determining the age of sedimentary rocks examined fossil remains of invertebrates.
However, in nature, there are a lot of harmful of this group.Many invertebrates are carriers of parasitic and infectious pathologies pests of grain and products from it.They can be toxic and cause damage to crops, forest, etc.
special place in the Group holds coelenterates.In describing traditionally indicate the presence of a radial symmetry, as well as two germ layers (ectoderm and endoderm).Usually, when it is considered that the body of animals is formed from two epithelial layers: the outer integument (epidermis) and the lining in the intestinal lumen (gastrodermisa).Between the layers is a jelly-like layer of connective tissue (mesoglea).It consists of collagen fibers present and amoeboid cells in a small amount.
Representatives Coelenterata no specialized respiratory organs and excretion.It is usually associated with a two-layer structure of the structure which provides the majority of epithelial cells in contact with the external environment.
to coelenterates characterized by underdeveloped nervous system.Most sexually reproducing and characterized by the presence of planktonic larvae or crawling.
