The scientists classify the existing known animals into invertebrates and vertebrates. The scientists have identified more than 46,900 vertebrates. Including carp, yellow croaker and other fish animals; snakes, lizards and other reptiles; frogs, Giant salamander and other amphibians; birds and mammals such as red pandas.
The scientists have also discovered more than 1.3 million invertebrates. The most of these animals are insects, and the most of insects are beetles. Meanwhile other invertebrates as insects are slugs, earthworms, squids, oysters, red starfish, jellyfish, spiders, corals, radiolarians, roundworms, pork tapeworms, sand silkworms, snails, Limax and other invertebrates.
Animals are a large group of multicellular eukaryotic organisms, but different from microorganisms. Animals can not synthesize inorganic substances into organic substances. They can only feed on organic substances. They are composed of cells with nucleus and no cell walls.Steel Tube Manufacturers
Therefore, animals have different morphological structure and physiological functions from plants as a series life activities like to feed, digest, absorb, breathe, circulate, excrete, sense, exercise and reproductive and so on.
Zoology classifies animals with the same or similar characteristics into the same category according to their morphology, internal structure of the body, characteristics of embryonic development, physiological habits and geographical environment.
According to whether they are aquatic or terrestrial, they can be divided into aquatic and terrestrial animals; according to whether they have feathers, they can be divided into feathered animals and featherless animals; according to whether there are spines in the body, we can divide all animals into vertebrates and invertebrates.
After the emergence of primitive life, with the change of living environment, millions of species continue to emerge and disappear. Only those species, which can adapt to the changes of environment, survive and multiply up to now. The evolutionary process of this species is biologically called evolution.