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3D Models of Animals ready made royalty free for 3D modeling.
In the scientific classification of living beings, the kingdom Animalia (in Latin, “animals”) or Metazoo (“metazoans”) is a large group of organisms that are eukaryotic, heterotrophic, multicellular and tissue (except poriferous ). They are characterized by their wide capacity for movement , for not having chloroplast (although there are exceptions, as in the case of Elysia chlorotica ) or cell wall , and for its embryonic development ; that is going through a phase of blastula and determines a fixed body plan (although many species can undergo a later metamorphosis ). The animals form a natural group closely related to fungi. Animalia is one of the four kingdoms of the Eukaryota domain, and to him belongs to the human being.
The best-known animal phyla appear in the fossil record during the so-called Cambrian explosion, which occurred in the seas around 542 to 530 million years ago. The animals are divided into several subgroups, some of which are vertebrates : ( birds , mammals , amphibians , reptiles , fish ) and invertebrates : arthropods ( insects , arachnids , myriapods , crustaceans ), annelids ( earthworms ,leeches ), mollusks ( bivalves , gastropods , cephalopods ), porphyry ( sponges ), cnidarians ( jellyfish , polyps , corals ), echinoderms ( starfish ), nematodes ( cylindrical worms ), flatworms ( flatworms ), etc.
n this field of transition can be mentioned, on the one hand, Proterospongia , coanoflagelado marine and planktonic that forms a gelatinous mass with choanocytes on the outside and amoeboid cells in the interior, and on the other to the small marine organism Trichoplax adhaerens ( placozoos edge) ) that forms a closed plate by squamous epithelium in the dorsal and cylindrical part in the central part, and presents in the inner cavity star-shaped cells; it is reproduced by flagellated buds and eggs. Another simple form of metazoan is Xenoturbella, who lives on the muddy bottoms of the sea. They have a few centimeters long and leaf shape, a ventral mouth that leads to a stomach-shaped sac. Between the epidermis and the intestine there is a layer of connective tissue with a longitudinal muscular tube and muscle cells in the mesenchyme ; in the basal part of the epidermis there is a nervous plexus and in the anterior part it presents a statocyst ; It produces ova and sperm , these identical to those of different primitive metazoans. Its systematic position is uncertain, having been proposed as a member of an independent phylum ( xenoturbélidos), perhaps to place at the base of the deuterostomes . As for the mesozoos , they are no longer considered a transition state between protists and metazoans ; their parasitic way of life seems to have led them to an extreme reduction and simplification from plumed worms .