In addition to all the other animals outside the protozoan general (metazoan sub-sector.) Metazoa metazoan In addition to the animal kingdom Protozoa door all multicellular animals other than general categories. Characterized by the body is divided by a large number of morphology, function of cells with division of labor; and both groups of protozoan nutrition and reproductive function in different cells, the germ cell and vegetative cell differentiation significantly. Institutional forms of symmetry according to the situation can be divided into asymmetric metazoan animals (phyla porous), radial symmetry animals (coelenterates door, comb jellyfish phylum, Echinodermata; the latter symmetry is secondary, the comb jellyfish and some corals are radial symmetry around), and bilaterally symmetrical animals (all other categories). Metazoan embryonic development in mesoderm differentiation in which the porous Phylum endoderm and ectoderm only the initial differentiation, coelenterates, including the door there in the layer between the ectoderm. Since the flat door after the animals are three categories of animal germ layers. According to the availability and structure of the body cavity can be divided into no body cavity metazoan animals, including porous animal phyla, phylum coelenterates doors and flat; leave the body cavity of animals, including animals, linear doors, doors, and other animals, abdominal hair; body cavity of animals, including all animals after the annelid category. In metazoan, the New Zealand insects have a complete digestive tract first, one end of the mouth, the other side of the anus. In addition, separation of the circulatory system and digestive tract, nervous system, more so than the Platyhelminthes. Paleontology, morphology and embryology of the evidence that: many metazoan cells from single cell protozoa. Not in the rise of multicellular animals, the single-cell animal has flourished. Single cell and multicellular animals animal groups, and there is no absolute hung between the structure, composed of many smaller cells (sometimes up to 50,000 cells) consisting of an empty spherical Volvox worm is between the single cell to multiple cells between intermediate type. What kind of single-cell animal the way through the evolution of the multicellular animals, the parties disagree. Main theories are: ① original theory of intestinal worms, 1874 Merkel first proposed the earliest ancestors of multicellular animals is similar to the spherical Volvox groups, these animals in a single cell retraction side of the formation of the ancestors of multicellular animals. Because they are very similar to gastrulation, two germ layers and the original port, so You Merkel of the original intestinal worms and to his doctrine of the original forest of the theory of intestinal worms. ② eat insects doctrine, Meiqi Kafelnikov observed many lower animals, embryonic cell development, such as found in some lower species, not primarily by the gastrula invagination method, but by the formation of the shift method. He also found that some multi-cellular animals, mainly phagocytosis was carried out by intracellular digestion, hate less for extracellular digestion. Therefore, he concluded the first multicellular animals appeared to intracellular digestion, extracellular digestion is the later development. Insects in a similar group that single-cell algae groups, some of phagocytosis after the food into the formation of groups within the endoderm, mesoderm results of the formation of two animals, initially for the solid, then gradually to the formation of digestive cavity, therefore, 梅契尼柯夫put this hypothetical ancestors of multicellular animals, insects called phagocytosis. ③ syncytial theory, Hatch and Hansen believe that the ancestors of metazoan and multinucleated ciliate should be similar to a single cell animals, and these multi-core cell division ciliates evolved multicellular animals. The doctrine that Platyhelminthes is no midgut is the most primitive metazoan. Ciliates from the original, I have evolved into both sides of the nuclear symmetry, ciliated, but not the size of the sub-nuclear non-intestinal type, while the other evolved into a higher size of the nucleus of the ciliate points. Metazoan metazoans In addition to protozoan, the general term for all other animals (metazoans sub-sector.) In metazoan, in addition to the animals and lateral animals (sponges) is really outside the metazoan (eumetazoa), which includes the group, from coelenterates (Cnidaria and the comb jellyfish phylum) onwards until the spine animals. Although metazoan multicellular animals also, but it is not only a cell group, cells are arranged according to two or three germ layers endoderm, and mesoderm, also known as the Animals (Germany keimblattie-re). In addition, because these cells both in morphology and function of the organization to differentiate into various shapes, also known as the Organization animals (De histozoa, gewebetiere) (in animals and sponges exception). Germ layers and tissue differentiation, the formation of various organs, thus maintaining the general metazoan system of higher animals. Related to this, metazoan ontogeny is generally complex. Single-cell egg through cleavage to form mesoderm, develop into embryos. During tissue differentiation and the formation of a certain shape at the same time, some go through a very complex after the formation of adult metamorphosis. Although asexual reproduction is sometimes, but mainly sexual reproduction. Department of metazoan ancestors from the protozoa had no doubt, but what kind of protozoa were discussing many of their ancestors. Roughly divided into: (1) is the result of multi-core cell differentiation in protozoa [Ha Dezi (hadzi) of ciliate origin, said that the class generated from the original multi-core flat ciliated animals, coelenterates is the resulting time animal nature]; (2) from the old doctrine of view, that kind of algae from the group evolved from flagellate groups. In both theories, the general argument that the former is less than [Ha Dezi (hadzi) than the doctrine of Bill (g.de beer) and more attractive], people are more in favor of the latter. The latter argument: that the structure of such groups is no change in metazoan germ; constitute groups of individuals have constructed in accordance with changes on the polar axis; differentiate into nutrition and reproductive a member of a member; in the process of forming groups, particularly similar to the ontogenesis of sponges; metazoan male germ cells to maintain the form of flagellates and so on. According to these materials, Haeckel (e.h.hackel) inferred ancestral metazoan animals and intestinal progenitor simultaneously.梅契尼可夫 (e. metchnikoff, 1886) is considered by planula larvae of coelenterates evolved. Based on the views of many scholars that the second theory is close to the truth. Metazoan really concerned with the body cavity, divided into the coelenterates and intestinal cavity body cavity body cavity of animals. The original animal was divided into the body cavity body cavity body cavity of class and true class [Ziegler (h.e.ziegler), 1889]. In addition, it was divided into the old port and new port animal animals into two categories [Groby because (c.grobben), 1908]. The other, there are classified into the mesoderm or the body cavity formation associated with terminal cell dry dry and intestinal cavity into two categories. Terminal cell dry class lower animals is equivalent to the original body cavity type, the other high and so the type and intestinal cavity dry like all the true body cavity type, terminal cell in the class and the old mouth of animals, consistent with intestinal cavity dry class and the new deuterostomes consistent. If the two classes are higher animals dry, you can see the body section. Comments above the doors of the metazoan phylogenetic relationships is important. Thus, it is easy to distinguish between vertebrates and invertebrates. Therefore, including invertebrates, including, a spinal cord of animals (the original cable animals), and phylogenetic relationships of vertebrates are attracting attention.
Translated by Google
Wikipedia Daquan
后生动物 百科大全
后生动物 百科大全
housheng dongwu Metazoan Metazoa In addition to the animal kingdom Protozoa door all multicellular animals other than general categories. Including porous phylum, coelenterate doors, flat doors, and other animals (see invertebrates). Characterized by the body is divided by a large number of morphology, function of cells with division of labor; and both groups of protozoan nutrition and reproductive function in different cells, the germ cell and vegetative cell differentiation significantly. Institutional forms of symmetry according to the situation can be divided into asymmetric metazoan animals (phyla porous), radial symmetry animals (coelenterates door, comb jellyfish phylum, Echinodermata; the latter symmetry is secondary, the comb jellyfish and some corals are radial symmetry around), and bilaterally symmetrical animals (all other categories). Metazoan embryonic development in mesoderm differentiation in which the porous Phylum endoderm and ectoderm only the initial differentiation, coelenterates, including the door there in the layer between the ectoderm. Since the flat door after the animals are three categories of animal germ layers. According to the availability and structure of the body cavity (Figure 1 Schematic cross section of the metazoan body) can be divided into no body cavity metazoan animals, including porous animal phyla, phylum coelenterates doors and flat; leave the body cavity of animals, including linear animal phyla, Phylum chest hair, etc. (see invertebrates); body cavity Animals (Coelomata), including all the animals after the annelid category. In metazoan, the New Zealand insects have a complete digestive tract first, one end of the mouth, the other side of the anus. In addition, separation of the circulatory system and digestive tract, nervous system, more so than the Platyhelminthes. Paleontology, morphology and embryology of the evidence that: many metazoan cells from single cell protozoa. Not in the rise of multicellular animals, the single-cell animals have flourished. Single cell and multicellular animals animal groups, and there is no absolute divide between, the many small cells (sometimes up to 50,000 cells) consisting of an empty spherical Volvox worm is between the single cell to multiple cells intermediate between type. What kind of single-cell animal the way through the evolution of the multicellular animals, the parties disagree. Main theories are: ① original theory of intestinal worms, 1874 E. Haeckel first proposed the earliest ancestors of multicellular animals is similar to the spherical Volvox groups, these animals in a single cell retraction side of the formation of the ancestors of multicellular animals. Because they are very similar to gastrulation, two germ layers and the original population, so called the gastrula Haeckel insects, called the doctrine of his original theory of intestinal worms. ② eat insects doctrine, NN Meiqi Kafelnikov observed many lower animals, embryonic cell development, such as found in some lower species, not primarily by the gastrula invagination method, but by the formation of the shift method. He also found that some multi-cellular animals rely mainly on the role of phagocytic cells to digest, very few for the extracellular digestion. Therefore, he concluded the first multicellular animals appeared to intracellular digestion, extracellular digestion is the later development. In a similar insect groups that single-cell algae groups, some of phagocytosis after the food into the formation of groups within the endoderm, mesoderm result of the formation of two animals, initially for the solid, then gradually to form a digestive cavity. Therefore, 梅契尼柯夫 put this hypothetical ancestors of multicellular animals, insects called phagocytosis. ③ syncytial theory, J. Hatch and ED Hanson that the ancestors of metazoan and multinucleated ciliate should be similar to a single cell animals, and these multi-core cell division ciliates evolved multicellular animals. The doctrine that Platyhelminthes is no midgut is the most primitive metazoan. Ciliates from the original multi-core evolution as a bilaterally symmetrical, ciliated, but not the size of the sub-nuclear non-intestinal type, while the other evolved into a higher size of the sub ciliate nuclear (Figure 2 animals evolutionary tree). Bibliography Jingbo et al: "invertebrate", People's Education Press, Beijing, 1982. (Huang Xiangfei)
