Highest animal kingdom such an animal. The common feature is a notochord in its ontogeny whole process or a period, dorsal neural tube and gill slits; including urochordate, head cable animals and invertebrates. Excluding these main features, chordates also has some minor features: closed circulatory system (except urochordate), such as the presence of heart, always in the digestive tract of the ventral; anal tail, which is located behind the tail anus , exists in a certain stage of life or the life cycle of existence; has the skeletal mesoderm formation. As for the mouth, bilaterally symmetrical, three germ layers, the true body cavity and the sub-section and other features are also having some invertebrates. Chordates named in 1874 by Heckel (ernst haeckel) According to the Russian embryologist Kovar Levski (А.О.Ковалевский) study, the sea squirt, amphioxus and vertebrate animals such as merger together and _set_ up this new door. Phylum of animals, including more than 40,000 kinds of modern existence, is divided into three sub-door: urochordate Amon, head cable and vertebrate animals Amon Amon. Chordates (phylum chordata) is species-rich and diverse gates. Since the door includes a vertebrate, so people conducted extensive research it. None of the spine chordates have very important significance in evolution. They are also sometimes referred to as original animal. The name of the former include Hemichordata account. Chordates are about 45,000 species, distributed in marine, freshwater, and terrestrial water between the environment between freshwater and saltwater. Some groups have evolved the ability to fly. More than 60,000 extant species, accounting for about 5% of the world's animal species. Including lampreys, fish, frogs, salamanders, snakes, lizards, turtles, alligators, birds, animals and other vertebrates, including some in small quantities, and only the lack of vertebrae notochord seafood animals, such as sea squirts and amphioxus, such as various . Back with a rod notochord, the door that the resulting animal naming.
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特征
The invertebrates anal hole is often an opening at the end of the body portion. The chordate heart and aorta of (5)
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下属分类
Ascidian into lanes are oblong, base to handle epiphytic submerged objects on the seabed or on the other end there are two not far from the hole: the top one into the water hole, the hole through the digestive tract in the middle the piece of cribriform the insulating film, and its role is filtered off and coarse objects, allowing only water and tiny food into the digestive tract; slightly lower position is a water hole (Figure 14-3). Embryogenesis and metamorphosis between two holes Ascidian back, corresponding to the side of the abdomen. Under normal circumstances, the water from the water into the hole and is discharged from the outlet hole, when disturbed by or stimulation, can cause sudden contraction of the body wall, the body area of the water reservoir like milk while spouting from the hole 2, respectively, so in the coastal areas of Shandong Province, commonly known as sea breast; to stimulate mitigation, the body gradually restitution. In addition to clusters intensive life, but also attached to other individuals of the same species itself can be other individuals attached the base stack Poly Health phenomenon.
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Relevant information
(1) chordates and invertebrates differences and relations ① notochord: chordates have a notochord runs back, after being replaced by the spine; invertebrates no notochord or spinal column. ② central nervous system: the chordate hollow nerve center located on the back; invertebrate CNS body was located in the ventral cord. ③ gill slits: All or part of the period of the life cycle of chordates have gill slits; invertebrates do not have gill slits. ④ the heart: the heart is located in the digestive tract chordate ventral; invertebrates heart at the back of the digestive tract. ⑤ biochemistry: chordate muscle contraction involved in energy metabolism in non-protein nitrogen-containing extract is creatine phosphate; invertebrates phosphate arginine. Chordata addition to the above features, it is also found in some structures of some invertebrates, such as the mouth, the three germ layers, bilaterally symmetrical, the true body cavity, the phenomenon of sub-section, closed tube blood circulation. See comparison between the two structures. Origins (2) chordates Is undoubtedly the invertebrate chordate origins. The genetic relationship among the echinoderms and chordates Hemichordata closer view of most people to accept. After speculated chordate ancestor may resemble urochordate larvae, which develop in two directions, one after metamorphosis, the adult who lives as a solid, with gill slits as feeding and respiratory organs; another direction is the larval stage extend and adapt to the new environment, no metamorphosis, producing gonads and reproduction (ie larvae sexual maturity), and to develop a new class of animals that have a notochord, dorsal neural tube chordate gill slits and the freedom movement. (3) appear in the notochord significance in the history of animal evolution Notochord is the emergence of animal evolutionary history of the major events that feature animal body support, protection and movement to get "quality" leap. The Herald structure to achieve a more perfect development in vertebrates, thus becoming the dominant one in the animal kingdom groups. Notochord (and spine) constitute the main beam supporting the body, is the weight of the force who make internal organs get strong support and protection, exercise muscles get strong fulcrum during exercise without leaving the body due to muscle contraction or shortening deformation , which is likely to "large-scale" development. Notochord axis supporting role also makes animals more effectively complete directional movement for active prey and escape predators are more accurate and faster. The formation of the vertebrate skull, jaw, and the emergence of the central nervous spinal protection is on this basis to further improve the technology development.
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Science knowledge
Chordates (Chordata) between the digestive tract and the dorsal neural tube has a longitudinal guide from mesodermal notochord or spinal animals. More than 60,000 extant species, accounting for about 5% of the world's animal species. Including lampreys, fish, frogs, salamanders, snakes, lizards, turtles, alligators, birds, animals and other vertebrates, including some in small quantities, and only the lack of vertebrae notochord seafood animals, such as sea squirts and amphioxus, such as various . Back with a rod notochord, the door that the resulting animal naming. Urochordate Amon (Urochoradata) are a class of small non-vertebral chordates seafood, totaling more than 1000 kinds, because the tail of a lifetime or larvae have notochord named. Common types are clava and Ciona and so on. Cephalochordate Amon (Cephalochordata) is distributed in temperate marine seaweed and fish-shaped chordates, about 30 kinds of the world, on behalf of animals amphioxus (Branchiostoma belcheri). Vertebrate (Vertbrata) is one of the most important groups of chordates, including round mouth Gang, cartilage Pisces, Osteichthyes, Amphibia, Reptilia, Aves, Mammalia seven categories of animals.
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Chordates (fossil)
jisuo dongwu men (huashi) Chordates (fossil) Chordates had included four Amon, Amon that Hemichordata, urochordate Amon, head cable and vertebrate animals Amon Amon (Vertebrata). The most important fossil chordates and compelling devaluation vertebrate fossils. Followed Graptolithina Hemichordata Amon in Cambrian to Early Carboniferous fossil is one very important category, widely distributed throughout the world. In recent years, due to the already established Hemichordata door alone, followed by pen fossils have been discharged outside the chordates fossils. Animals have long been the first cable was not found fossils, discovered in 1981 reported the first cable in the Permian fossils in South Africa. Urochordate fossils so far only a few reports. B. Pyle Switzerland has some of the prints found in the Oligocene shales interpreted as ascidians, but has not been recognized by biological and paleontological circles. In recent years, also found some tiny traces of southern China in the Early Cambrian black shale, is considered urochordate Amon-shaped outline of young animals fossils. However, due to years too long (about 600 million years ago), the individual is too small (only 8 to 12 microns, which is about 0.1 mm, less than some extant urochordate sperm) and biological structure is not clear, not biology and paleontology field recognition. Others such as the Burgess Shale fossil vertebrates suspicious Pi-kaia like. 1967 RPS Jefferies raised originally Echinodermata Haibian Goa door sea pile Gang (Stylophora) again Yingzhu chordates calcium in a separate cable animals Amon (Calcichordata). He claims that all animals have a calcium large and heavy, head and a tail covered with bony plates of calcium carbonate. On the fossils found some with chordate pharynx, gill slits, brain, epicardial, mesenteric mouth, esophagus, rectum and other structural features relative ratio. And that only a pile of animal calcium cable first Gang (Stylophora) an outline, under which is divided into the first corner than the original mesh (Cornuta) and first class evolved from the corner of the first mesh cap (Mitrata). The head rope animal ancestors first project with cap found in Bohemia in the Czech Ordovician necked bags first La □ ynocystis related urochordate ancestors with the same cap the first heads produced in Bohemia Middle Ordovician of oak bags first Balanocystites relevant; whereas vertebrate ancestors may be found in Bohemia and France in the Upper Ordovician and Lower Devonian of Germany cap bag first Mitracystites ancestor type. But this view has not been all biologists and paleontologists accept. Vertebrate almost every project has a large number of fossils, and some extinct projects and classes. Vertebrate Paleontology specializing in Vertebrate fossils and related vertebrate origin, evolution, and other issues related to the geographic distribution of the different geological history, paleontology become an important branch. (Collins)
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