Animal

Vertebrates are characterized by a spine composed of connected vertebrae. They are a relatively advanced category of animals. They are generally divided into three parts: head, trunk and tail. The body shape is symmetrical. The trunk mostly has pairs of appendages. Aquatic animals have pectoral fins and pelvic fins, and terrestrial animals have forelimbs and hindlimbs. There are three types of reproduction, namely oviparous, ovoviviparous or viviparous. Vertebrates can be divided into six classes: Cylastomata, Fish, Amphibians, Reptiles, Birds and Mammalia. Invertebrates are characterized by the absence of a spine on their back. They are the primitive form of animals and account for 95% of the total number of animal species. Distributed all over the world, there are about 1 million existing species, including echinoderms, molluscs, platyhelminthes, annelids, coelenterates, arthropods, sponges, nematozoa, etc. With such a rich animal world, how do we classify them? It was in the 18th century that the Swedish naturalist Linnaeus began to create the binomial method of naming animals and plants. Under his influence, animal taxonomists divided animals into seven main levels based on their various characteristics, namely kingdom, phylum, class, order, family, genus and species. This is the most comprehensive classification of animals. This book mainly includes endangered animals in my country, globally endangered animals, rare animals in the world, strange-looking animals, marine animals, invertebrate protozoa, porous animals, coelenterates, platyhelminthes, linear animals, annelids, molluscs, echinoderms, arthropods, as well as vertebrate fish, cartilaginous fish, fish hard fish Osteichthyans, amphibian anurans, amphibian anurans, amphibian anurans, extinct reptiles, reptile squamates, reptiles turtles, avian ratites, avian penguins, avian protothoracids, mammal prototheria, mammalian eutheria, etc.