What are the characteristics of traditional music in China? What are the cultural factors that lead to this feature?

At present, there are about 1.5 million species of animals in the world, which can be divided into two categories: unicellular protozoa and multicellular metazoa. The species of metazoa are dozens of times more than protozoa, which can be divided into two categories: one is that the cells of animals only have different differentiation, such as porous animals (sponges); The cells of another animal have a division of labor and can form a completely fixed system of tissues and organs. Multicellular animals except porous animals all belong to this category. In addition, most zoologists are used to dividing the whole animal kingdom into invertebrates and vertebrates according to whether there are vertebrae in animals. This division is not very scientific. To be exact, animals should be divided into two categories: chordates and chordates.

There are more than 150 buildings with rebellious tendencies. ...

Although I don't like China's music either, it's not easy to evaluate.

Maybe it's something we don't understand .. but it also has its value, which is an undeniable fact.

I think the characteristics of China's music should be: joy and sadness.

Responder: Ami- trainee magician level 2 6-4 14: 16.

Among the 10,000 species of animals, the vast majority belong to invertebrates, and vertebrates account for only a small part. It is a subfamily of Chordata. Zoologists tend to classify invertebrates into 3 1 phylum in recent years. Some people abroad include Placozoa established by Professor Grell of West Germany 197 1 and Loricifera established by Kristensen of Denmark in recent years, which divides invertebrates into 33 phyla. Although there are great differences in animal species, it is generally believed that they are all descendants of the same ancestor, have a certain kinship, and are the products of long historical development.

Most scholars agree that all animals can be divided into individual species (reflecting historical discontinuity) and summarized into large and small groups (reflecting historical continuity), both of which are the basic contents of taxonomy. Species is the basic unit of classification, and it is the unit that people know and distinguish animals. From a historical point of view, no matter how big or small a group is, it must have its origin process from scratch and its development process from vertical to horizontal. On the one hand, diversification (increasing the number of species), on the other hand, complexity (improving the level of organisms). Due to the change of living conditions or other reasons, the structure of some animals is complicated, or new organs are produced, or the structure of old organs becomes more complicated; Because of the related variation of organs, some organs have changed and some have also changed. In addition, when animals transition to a fixed lifestyle or a parasitic lifestyle, there will also be a one-way specialization process, that is, some organs develop and others degenerate sharply. Therefore, the evolutionary process is not a simple continuous development of animal structure, but a complex process in which evolution and degeneration coexist.

The existing animals were developed from ancient animals. In addition to the characteristics preserved from their ancestors, they also developed the characteristics that their ancestors did not have and adapted to the new living conditions. New evolutionary variations may occur not only in adult animals, but also in different periods of their lives. All kinds of groups in the animal kingdom have evolved from single-celled organisms of the same ancestor. It is generally believed that both the animal kingdom and the plant kingdom come from the same ancestor. Single-celled organisms with autotrophic and heterotrophic pigment bodies may be the most primitive animals, while heterotrophic animals that generally feed on plants or other animals appear later.

The most primitive protozoa may be primitive protozoa. Among the existing protozoa, flagellates may have evolved from this primitive flagella, and other kinds of modern protozoa have also evolved from it. Multicellular animals originated from single-celled animals, but how single-celled animals evolved into multicellular animals has been inconclusive. Some people think that multicellular animals originated from primitive polynuclear ciliates. When their cytoplasm divides and surrounds every 1 nucleus, they form a multicellular entity with cilia. But most zoologists believe that multicellular animals evolved from group flagellates. Although the primitive group of flagellates still belongs to protozoa, the cells have already been related, such as the existing Volvariella volvacea, the differentiation of vegetative cells and reproductive cells, and the cells are connected by protoplasm bridges, so the individuals in the group have lost the ability to live independently. Therefore, organisms like Volvariella volvacea are considered as a form of transition from single-celled animals to multicellular animals.

Meso-zoa is a tiny parasitic animal living in the ocean, and it is the simplest and strongest primitive multicellular animal. Because the DNA in its nucleus contains 23% guanine and cytosine, which is similar to protozoa and lower than that of oblate animals, it is considered to be the most primitive metazoa and a type between protozoa and metazoa.

Sponges are a very old group. Because it has collar cells, it is very similar to protozoan flagellates. So people think it evolved from primitive flagellates. But it was separated from the trunk of multicellular animals very early; Because of its turnover in embryonic development, porous animals become a special blind branch in the evolution of 1 animals, which are called lateral animals (or turnover animals), while all other multicellular animals are collectively called eumulticellular animals or Eu-metazoa.

True multicellular animals first developed coelenterates with radiation symmetry. It is a typical twin-embryo animal with digestive cavity, which may come from the ancestor coccidia similar to planktonic larvae, develop into primitive jellyfish type, and then develop into fixed hydra type and complex free-swimming jellyfish type. The comb jellyfish is a kind of free-floating animal, similar to jellyfish, and its body shape is basically radial symmetry, but the radial symmetry on both sides is obvious. There are some special structures, such as mesoderm primordia instead of stinging cells. In recent years, most zoologists advocate that it be listed as an independent door.

When animals transition to crawling life, it will cause head differentiation, bilateral symmetry and mesoderm development. Among the evolutionary branches of primitive tricodermata, Protozoa and Bacorata show many important evolutionary characteristics in structure and function. Animals that develop from the original mouth (embryo hole) to the adult mouth in the embryonic stage of gastrula are collectively called protozoa. In addition to the larger phylum Platycladus, Arthropoda, Rotifer, Nematoda, Nematoda, Mollusca, Annelida and Arthropoda, there are some small phylum belonging to protozoa.

The most primitive phylum of protozoa is the phylum Platycladus, which has no body cavity. It may be that the ancestors of planktonic larvae first evolved into the most primitive annelids, while the parasitic flatworms obviously evolved from free-living species, and finally evolved into internal parasites (such as tapeworms), thus causing a series of organ changes, such as the digestive system tends to degenerate (tapeworms) or even disappear completely (tapeworms). Nemertinea, a few animals, also belongs to the class of aneurysmal animals. It not only has anus and developed cephalic ganglion, but also has primary closed circulatory system. In addition, it also has some characteristics of a side door, such as ciliated epithelium and protorenal duct. It may be a flatworm that lives independently. Nematode jaws, established in 1972, is also an aneuploid animal. The mouth is located on the ventral surface without anus; Although there is no body cavity, there is little matrix and only a single layer of ciliated epithelial cells. In evolution, they seem to be related to both flat animals and prosthetic cavity animals.

Prosthetic cavity is formed from embryo blastocyst cavity to adult, not mesoderm, and there is no body cavity membrane between body wall and digestive tract. Seven phyla (rotifer, Gastropoda, Nematoda, Echinocephala, Anisoda and Internal Anus) in the animals with prosthetic cavities are not a natural group, and all phyla have prosthetic cavities, but others are quite different. Therefore, their genetic relationship is difficult to determine, and only rotifers and gastropods may be related to platycodon grandiflorum. Prosthetic coelenterates are more advanced in evolution than animals without coelenterates, but they have not developed further. They are also some blind branches of evolution and a group between coelenterates and true coelenterates.

In mollusks and protozoa, a real cavity began to appear. Its true cavity is formed by split cavity method, but it is underdeveloped and only exists in pericardial cavity, kidney and gonad cavity. Because molluscs are spiral cleavage and bear wheels, it shows that molluscs may come from the ancestors of bear wheel type. Charophyta is similar to the mollusk larvae of marine flounder in morphology, and the most primitive mollusk still has ladder-like nerves, which indicates that it may be related to flounder. The most evolved branches of protozoa are arthropods and arthropods. Lower annelids also have spiral cleavage and trochlea, which are similar to mollusks, indicating that they have the same origin. But annelids appear segmented and appendages, and the mouthparts are more developed. In addition, there is a closed circulatory system and chain-like nerves, which are more advanced than mollusks. Although annelids and mollusks originated from the same ancestor, they evolved in different directions. Because the appendages are segmented and further complicated, the structural level of the animal body has improved a lot, resulting in the largest variety of arthropods and the widest range of adaptation. Arthropods are the culmination of the evolution and development of protozoa, with segmented body and exoskeleton protection; Segmented appendages, developed muscles and chain nerves make the structure flexible and powerful. There is no doubt that they come from annelids, but zoologists still hold different views on whether their origin is single source or multi-source. Some people think that the extinct trilobite is the most primitive, evolving from 1 to chelate suborder, and 1 to crustacean; Other primitive arthropods, such as Zhou Gang, branched from 1 to polypod, and branched from 1 to Insecta. However, some people think that different groups of arthropods are the ancestors of arthropods, and the different groups of arthropods evolved along three main directions, namely trilobites, chelates (xiphophora and arachnida) and jaws (crustacea, Polypoda and Insecta). Therefore, it is considered that arthropods are multi-source. The development of the three branches is carried out along the road of variation with the same method, which not only changes the form, but also changes some lifestyles from aquatic to terrestrial. Insecta is undoubtedly the senior representative of Arthropoda.

Echiuridea is very similar to Sipuncalida, such as spiral division, trochanteric body, sarcoidosis, and the body cavity is not separated. The posterior renal duct also plays the role of reproductive duct. The difference is that the intron of the starworm is not homologous to the kiss of the cockroach, and the starworm has no traces of bristles and segments. Priapulida has a real body cavity, and the larval stage is similar to the adult stage. Its evolutionary position needs further study and determination. Crustaceans with claws attached to their limbs, slow-moving animals with a body size of no more than 65,438 0 mm, and five orders with parasitic life are three branches separated from the ancestors of annelids a long time ago, but they have surpassed annelids in evolutionary level. They all belong to close relatives of arthropods. There are also three different types of small branches from primitive Triceratops, which have appeared since CAMBRIAN, such as ectoderm, brachiopod and flea, and their anus is open outside the tentacle crown. All three groups are sedentary, with mouthparts, posterior kidneys and tentacle crowns. However, whether there is a direct genetic relationship between them in evolution has not been completely determined, but it is unanimously recognized that they are between protozoa and metazoa. In the past, the internal anus and external anus merged into bryozoa, but the former was a pseudocoelenterate and the latter was a true coelenterate. Nowadays, most zoologists think that these two doors should be independent.

Animals whose original mouth in gastrula stage becomes an adult's anus, and whose end opposite to the original mouth re-opens into the adult's mouth are collectively called posterior-mouthed animals. They form mesoderm by intestinal cavity method and have endoskeleton formed by mesoderm; The nervous system is rope-like or tubular; There is a true body cavity. Metazoa include chaetognathus, echinoderms, Brachionus rotifers, Hemiechinoderms and Chordata. Hairy jaw animals are similar to protozoa in body wall structure, digestive tract and body cavity membrane, and are a special branch of the latter. The rest of the houkou animals were developed by the ancestors of the feather-wrist larvae similar to the existing echinoderms. Most representative animals of Echinoderm are radiation symmetrical (secondary phenomenon, larvae are bilateral symmetrical), which is related to the transition to fixation or little activity. In the further evolution and development, some animals have re-formed bilateral symmetry. In the past, Pogonophora has always been regarded as the most advanced invertebrate. However, since 1970 discovered segmented and bristly caudate species, some people think that they are related to polychaetes of annelids. Therefore, the evolutionary position of brachiopods is still controversial. Because half-spiny salamander (such as stigma) only has embryonic notochord (oral notochord), although it has 1 imperfect dorsal neural tube and branchial fissure, it still has ventral neural tube, and its larvae are very similar to echinoderms starfish. Therefore, it is not placed in chordates at present, but in a position between invertebrates and chordates. From the evolution of invertebrates, we can see that their structure and function have changed from simple single cell to complex multi-cell; From two germ layers to three germ layers; From radial symmetry to bilateral symmetry; The body has never been segmented into knots; From no appendages to appendages, and then to segmented appendages; The evolution of body cavity from anhydrous body cavity to prosthetic body cavity and then to real body cavity is beneficial for animals to better adapt to various living conditions on land and water, and all kinds of animals have close or distant kinship. Although protozoa have played an important role in evolution, metazoa are the backbone of the whole invertebrate, and invertebrates have evolved into more advanced chordates.

Most zoologists believe that chordates originated from echinoderms. As for the ancestors of chordates, they may be primitive headless animals, which are specialized into two branches, namely, caudate animals (such as sea squirts) that live in a fixed life and cephalochordates (such as amphioxus) that tend to live underwater. Amphioxus has 1 notochord, hollow dorsal nerve canal and branchial fissure. Primitive cephalopods evolved from the spine of primitive headless animals, that is, the ancestors of vertebrates. Chordata and branchial cleft of higher animals only exist in embryonic stage. Chordata include Chordata, Cephalotaxus and Vertebrates. Chordata evolved from primitive headless to primitive headless; From jawless (fossil turtle, round mouth) to jawless (fish ancestor); From aquatic organisms to terrestrial organisms; Never containing amniotic membrane to containing amniotic membrane; From warm-blooded animals to warm-blooded animals. The earliest vertebrates appeared in fresh water, and the Silurian and Devonian of Paleozoic were called the "Fish Age". Shield fish, cartilaginous fish and bony fish have appeared since Silurian, but shield fish became extinct at the end of Devonian, while cartilaginous fish and bony fish still thrive in various waters. Amphibians appeared in Devonian and reached their peak in Carboniferous of Late Paleozoic. At the end of Carboniferous, reptiles evolved from primitive amphibians. In the Mesozoic era, the whole nature was almost occupied by reptiles, so it was often called the "reptile era". At present, it is generally believed that reptiles probably originated from Carboniferous salamanders in amphibians, especially sauropods in this class.

1.400 million years ago in the late Jurassic, the earliest birds appeared. Birds originated from reptiles. In Neogene and Tertiary, the species of birds increased significantly, mainly because their body temperature was constant, which reduced their dependence on the environment, and also because they adapted to the flying lifestyle, became specialized in morphological structure and physiological functions, and gradually developed into modern birds. Mammals (mammals) also originated from reptiles (foraminifera). By 70 million years ago, in the early Cenozoic era, a series of progressive features had gradually appeared in the long-term historical development of mammals. Therefore, mammals have replaced reptiles and occupied a dominant position in the animal kingdom, so the tertiary period of the Cenozoic era is often called the "Mammalian Age".

According to their evolutionary history, zoologists have artificially constructed 1 evolutionary tree. The branches under the tree represent ancient animals; They keep their original structure. The branches at the end of the system tree are separated from the trunk in different historical development stages. When constructing the phylogenetic tree of animal kingdom, we should not only consider the structure of modern adult animals and fossil adult animals, as well as their surrounding environmental conditions, but also consider their individual development characteristics. Only in this way can the system tree be closer to the actual situation.