May 28, 2022
Vertebrates (Vertebrata; Vertebrates are also characterized by a distinct head part that carries the sense organs (olfactory, visual, auditory-balance) and contains a three-part brain that processes signals from the sensory organs and coordinates the body's activity. In the embryonic development of the head and other parts of the body, neural crest cells, which form during neurulation, migrate around the embryo's body and contribute to the formation of many tissues and organs, are of particular importance in vertebrates. Due to the active way of life of vertebrates, a number of other evolutionary novelties associated with higher demands of metabolism can be found in them (eg heart, erythrocytes, improved gill water supply due to muscle, specialized digestive glands, kidneys, etc.). A very important innovation of vertebrates is also their unique adaptive immune system based on B and T lymphocytes. Very early in the evolution of vertebrates, there was a double duplication of the genome, which probably supported the plasticity of regulatory mechanisms and facilitated the evolution of new structures. Among the vertebrates, there are over 70,000 described species. More than half of them are quadrupeds, ie terrestrial vertebrates - amphibians, reptiles, birds and mammals. Although birds traditionally belong to a separate class, they are actually a subgroup of reptiles, as they are the direct descendants of theropod dinosaurs and are the closest living relatives of crocodiles. The echinoderms are evolutionarily close to ewes and latimeria, together they are among the finfish. The vast majority of the remaining vertebrates are ray-finned fish. Another group of primarily aquatic vertebrates are fish, whose best-known representatives are sharks and rays. Primitive vertebrates, which, unlike others, do not have formed jaws, are represented in today's fauna by a small group of roundworms represented by mihules and mucous membranes. The mucous membranes are very reduced in many respects, for example they have some stunted sense organs and they lack typical vertebrae. Even for these reasons, they were sometimes not considered true vertebrates, the group of vertebrates was then narrowed only to mihule + jaws. For the group, which also included mucous membranes, the name Craniata began to be used. Due to the fact that the affiliation of mucous membranes among round-mouthed, and therefore also among "true" vertebrates, is now confirmed by molecular and morphological data, they become designated vertebrates and cranial synonyms. sporadically, but in the Silurian and especially Devonian, there is a rapid development of groups with bone tissue forming exoskeletons and endoskeletons. Thus, a number of fossils are available documenting some revolutionary events in the evolution of vertebrates, such as the formation of jaws from gill arches or the late Devonian colonization of land. Aquatic animals of all times are vertebrates. On land, these are sauropod dinosaurs from the Mesozoic period, the largest creature ever is a giant flounder.