In zoology, generally refers to simple body structure, tissue and organ differentiation is not significant invertebrates.
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No. 2
"Higher animals" relative term. Generally refers to a simple body structure, tissue and organ differentiation was not significant, without a spine invertebrates. In zoology, and the higher animals without clear boundaries.
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No. 3
On Earth at least 90% of animal species belong to the lower animals. Some lower animals, the body is soft, some students have to do with a protective shell. Lower animals, including sponges, cnidarians, echinoderms, insects and other animals of about 20 doors. Animals other than insects, which in addition to the door, the majority of species live in the ocean, such as starfish, sea urchins and so on. In the evolution of lower animals, their physical structure has undergone great changes, has gone from low to high, from simple to complex evolution. Classification of porous phylum Now there are about 10,000 kinds of sponges known, mainly based on the composition and shape of bone needles, divided into the following three key link. 1. Gang calcarea calcareous sponge With calcareous spicules, are small, white, single groove type or ditch system Shuang'gou type. Normal habitat in shallow water areas. Such as white sticks sponge leucosolenia, hair pot grantia and so on. 2. Six put sponge Gang hexactinellida Placed with six shaped siliceous spicules, of big, complex ditch ditch system type, flagella room large. Dwelling in the deep zone. Calamagrostis mediated hyal0nema and long marriage as the same hole euplectella. 3. Gang demopongiae unusual sponge Placed with non-six-shaped siliceous spicules or sponge wire, ditch the Department re-groove type, flagella room is small, irregular shape. Habitat in fresh water or sea water. Habitat in the sea, such as Beihai wear cotton cli0na, bath sponge eusp0ngia; habitat in fresh water such as freshwater sponges spongilla needles and so on. Medicinal species are mostly ordinary sponge Gang. Common, such as brittle needles sponge sp0ngilla fragilis lecidy, dials sponge ephydatia mulleri var. Japonica (higendorf) and so on. Porous primitive multicellular animals as animals, also known as the phylum sponges door (spongiatia), commonly known as sponge (sponge). Sponges are important reef, a few species have certain stratigraphic significance. Sponge raw animal tissues, no real digestive cavity and nervous system. Although the division of cells in sponges, but cooperate with each other even slightly, such as sponge ground screening, which separated the cells can survive for several days (the equivalent of protozoa). However, if no longer with each other, we can not continue to survive, sponges and cooperation that is independent of the characteristics that its structure remains cellular organism level, shows the original characteristics of multicellular animals. Sponges and more for the group, the monomer less. Body was symmetrical or asymmetrical radiation. Changes in the shape of a large group. Monomer for the pyramidal general, disk-shaped, goblet-shaped, spherical, etc. Size of the change from a few millimeters to 2m between. Most have calcium, silica, or horny skeleton. Sponges have spicules of bone (sponge-pin), sponge wire (bone wire) and non-mineral bone needle three. Spicules composed of calcium (calcite, aragonite) or silica (opal). Spicules can be divided according to the size of a large bone needle and a small bone needles. Horny sponge wire components of organic compounds, were filamentous, branching, or handover together. Silk sponge perishable, difficult to form fossils. Sponge's reproductive and sexual availability of two. In addition to the modern sponge sponge outline of a few common types are freshwater sponges, the majority of marine animals, benthic sessile camp. Sponge sponge and calcium modern rock scattered in shallow water areas, but the glass sponge inhabit a depth of 6000m in the deep ocean. Fossil sponges are also generally require similar water depth. Sponges often in a different geological age and layer foraminifera, bryozoans and algae together to form a reef. Important representative fossils Ordinary sponge Gang (demospongea) Glass sponge Gang (hyalospongea) Hard sponge Gang (sclerospongea) Coelenterate door features Coelenterate body has a fixed shape, and radial symmetry, that is, through the central axis of the body there are many facets of the body into symmetrical halves. Only the surface and back on the mouth side of the points. Some species are only two section through the central axis, the body is divided into equal halves, said two radial symmetry, such as sea anemones. This is between the radial symmetry and the symmetry between both sides of a form. Second, the two primitive germ layers and the digestion chamber Third, cell and tissue differentiation Coelenterate skin cells have differentiated into muscle cells, glandular cells, between cells, gill cells, sensory cells and so on. Skin-muscle cells are the cells within the ectoderm of the main executable epithelial and muscle physiology, it is called skin-muscle cells, which suggests that began with the primitive coelenterate epithelial and muscle tissue. Skin-muscle cells in the base of the extension of one or a few slender processes, including muscle fiber distribution, their composition and mechanism of contraction is similar to higher animals. Fourth, the network nervous system Began to appear from the coelenterate nervous system. Neurite to nerve cells linked to each other from a network, so called mesh nervous system. Nerve cells in the sensory cells within the ectoderm, skin-muscle cells connected to the outside world an effective response to various stimuli, but not the nerve center. Nerve conduction generally do not have a fixed direction, so the nervous system known as dispersion. Coelenterate not breathing and excretory organs, mainly rely on the cell surface to obtain oxygen from water and carbon dioxide and other waste directly into water or into the digestive cycle cavity from the discharge port. Fifth, a hydra-based, two basic forms of jellyfish-type Camp sessile polyp type, takes the shape of cylindrical, terminal, said base plate fixing the other end for the feeding of the mouth, surrounded by tentacles, in the thin layer. Gang of coral polyp type, the body wall ectoderm secrete calcareous exoskeleton. Floating jellyfish-type camp life, takes the shape of disc-shaped, prominent side, said outside the umbrella, under the umbrella, said concave side, the central suspension of a vertical pipe, tube end is the mouth, through the mouth into the digestive cavity and sub-loop The radiation tube branched, and has been connected through to the edge of the umbrella ring, the edge of the umbrella tube with tentacles and feel (balance capsule, tentacle sac). Hydromedusae umbrella from the next film around the edge to the central stretch, said border membrane. Six, reproductive methods Availability of reproductive and sexual reproduction two. Asexual budding often form groups. Mostly dioecious sexual reproduction, the polyp ectoderm formed by the outline of the gonad, but the key link Scyphozoa and the gonads of coral comes from the endoderm, between cells from the germ cells. Seafood species during embryonic development in planula stage. The main features of the door Platyhelminthes Platyhelminthes in animal evolutionary history occupies an important position. Began to emerge from such a bilaterally symmetrical animals, and mesoderm, which animals further complicates the structure and function, improvement and development of animals from aquatic to terrestrial transition laid the necessary foundation. Related to this animal in the flat stages of the original drainage system and the ladder-like nervous system. (A) bilaterally symmetrical animals began to appear from the flat side of a symmetrical body, through the animal's central axis, only one plane of symmetry (or that section) about the animals into two equal parts, so both sides are symmetrical called symmetrical. Evolution from the animal point of view, this was mainly due to animal body floating in the water of life from crawling into the bottom of life results. The development of this size has been the evolution of animals is important. Because all bilaterally symmetrical animals, the body can clear separation of front, left, dorsal. Body on the back of the development of protection functions, the development of a ventral movement functions, always the first contact with the forward end of the new external conditions, to promote the growing nervous system and sensory organs to the body of the front focus, the gradual emergence of the head, making the animals from the non-directional movement into directional movement, so that more accurate sensing of animals quickly and effectively, to adapt them to a wider range. Symmetrical on both sides is not only suitable for swimming, but for crawling. Possible evolutionary crawl from the water to crawl on land. So both sides of the symmetrical development of aquatic animal from the important to terrestrial conditions. (B) the mesoderm from the beginning Platyhelminthes, between the ectoderm and the inner embryo appeared in the embryo. Mesoderm of the emergence of animal structure and function of the further development of great significance. On the one hand because the formation of mesoderm reduced, the ectoderm of the burden, causing a series of tissues, organs, systems division, for the animals further complicated by a complete body structure provides the necessary material conditions to make up the organ systems Platyhelminthes level. On the other hand, due to the formation of mesoderm, and promoted to enhance metabolism. Such as Chinese and mesoderm formation of complex muscle layer, enhanced motor function, coupled with the bilaterally symmetrical body, the animal may be in the context of a larger intake of more food. And because the walls of the digestive tract has also been a muscle, the ability to make digestive tract motility also increased. These undoubtedly contributed to the strengthening of metabolic function due to enhanced metabolism, metabolic waste produced also increased, thus promoting the formation of the excretory system. Platyhelminthes start with the original drainage system - the original renal tubular system. Also, because the animals, motor function improved, regular contact with changing external environment, to promote the nervous system and sensory organs of further development. Platyhelminthes than the coelenterate nervous system has been significantly advances have begun to focus on the nervous system for the ladder. In addition, the Chinese and the real germ layers formed organizations store nutrients and water features, animals can withstand some degree of hunger and drought-resistant, therefore, mesoderm formation is the evolution of animals from the aquatic to the terrestrial one of the basic conditions . (C) the skin and muscle sac mesoderm formation as arising from a complex structure of muscle, circular muscle, longitudinal muscle, oblique. And the formation of epidermal ectoderm close to each other and the composition of the body wall called the "skin and muscle capsule", it formed a protective function in addition to muscular system, but also enhanced motor function, with bilaterally symmetrical, so that animals can be more faster and more effectively to food intake, more conducive to the animal's survival and development. In the skin-muscle within the capsule, the parenchyma of the filling, all the organs of the body are embedded in it. (D) is similar to the digestive system and general coelenterate, both through the mouth to the hole in vitro is the anus, only a single head planarian pharynx, such as single swallow insects (haplopharynx) a temporary anus, so called imperfect digestive system. In addition to large intestine, no other body cavity. Intestinal endoderm by the formation of the blind tube, the type of business parasitic life, the digestive system tends to degradation (eg Trematoda) or completely disappear (Cestoda). (E) drainage system began to emerge from the Platyhelminthes renal tubular excretion of the original system. It exists in the door animals (other than non-intestinal target) of all taxa. The original tube from the kidney into the formation of the ectoderm on both sides of the body, usually with many branches of the excretory duct structure, a whole body vent outside. Most end of each small branch from the flame cell (flame cell) composed of blind tube. Actual flame from the cap cells and cells are composed of duct cells. (F) the nervous system of Platyhelminthes than the coelenterate nervous system has been significant progress. Expressed in nerve cells gradually move focus to form a "brain" and from the "brain" backward vertical separation of a number of longitudinal nerve cord in the nerve cord is connected between the horizontal nerve. In higher species, longitudinal nerve cord reduced, only one pair of ventral nerve cord development, which horizontal neural connections, such as trapezoidal (or ladder-type nervous system) has a brain and nerve cord nerve fibers in contact with body parts. Animals can be said that the original flat central nervous system. Nervous system, although this network coelenterate nervous system than advanced, but it is the original, because the brain would not focus exclusively on the "brain", but also scattered in the nerve cord. (Vii) the majority of hermaphrodite reproductive system, as the emergence of mesoderm, the formation of male and female germ cells have fixed some of the gonads and reproductive ducts, such as the fallopian tubes, vas deferens, as well as a series of subsidiary gland, such as the prostate gland and other egg yolk. This can pass to the germ cells in vitro, in vivo fertilization and mating line. Platyhelminthes camp life of free-living or parasitic, free-living species (such as the planarian Gang) located in the sea, fresh water or moist soil, carnivorous. Parasitic type of life (such as Trematoda and Cestoda) are parasitic on other animals, body surface or body, the intake of the animal nutrition. Echinodermata (echinodermata) the animal world body cavity of an animal. Radial symmetry, a unique water system. Separation of body and digestive tract in the true body cavity, body wall are derived from the mesoderm within the bone, bilaterally symmetrical larvae, development through a complex metamorphosis. The mouth hole on the opposite side from the embryo occurs, is deuterostomes, the evolution of invertebrates in the high status. Include starfish, brittle stars, sea urchins, sea cucumbers and sea lilies, etc. (Figure 1). Because the epidermis is generally named after a spine. Full of seafood. Are about 5900 kinds of students, China has discovered 500. Look very different forms, there are star-shaped, spherical, cylindrical and flower. Release of radiation into the body of five symmetrical arrangement shown by the tube feet. According to whether the tube foot, the body is divided into a tube or step foot spoke with the Ministry and unregulated foot step between the spokes or indirectly with the Ministry. Internal organs, including the water system, nervous system, blood system and reproductive system are radial symmetry, except only the digestive tract. As the radial symmetry, body surface and back on the mouth side of the points. Although the doors of the outline shape are very different animals, but its basic structure is the same. Starfish and brittle stars was the star class, the upper and lower flat, the body axis is very short, flap side down, tube feet along the wrist (radial Department) for the radial arrangement. Sea urchins and sea cucumbers to extend the body axis, radial spokes between the Ministry and the Ministry of combination takes the shape of spherical or cylindrical, tube feet for radial order. Crinoids for the mouth, back on the mask for long-handled or attached to sticks with volume (Figure 1). Echinoderm skeleton is developed by a number of separate calcium carbonate composition of the bone plate, the plate by a single crystal of calcite. Bone outsourcing epidermis, the skin usually with spines. Sea urchins and starfish have different fork spine. The most advanced sea urchin skeleton, bone healing into the shell plate closely. Starfish, brittle stars and crinoids into the carpal plate-shaped vertebrae. Sea cucumber least developed bone, into tiny fragmented pieces of bone or bone needle. Echinoderm adult body cavity structure mainly occupied by digestive and reproductive systems, but crinoids body cavity filled with connective tissue membrane and cable. Water by the body cavity of the part - the water chamber evolved. Moving, feeding, breathing and feeling all rely on it to complete. Typical water pipe system from the sieve, through stone pipes, pass to the ring around the mouth of the Ministry of radial spokes and stretch tube. Radial branches assigned to a small tube tube feet. Tube feet are the base of the altar capsule, the end of a suction cup, filled with sea water, by stretching the muscles move the meter body. Nervous system, blood system and water system has a ring around the esophagus and radiation from the ring to each part of a main branch. There are three echinoderm nervous system: ① aperture, said outside the nervous system or nervous system in the epidermis or the epidermis, including the nerve ring around the esophagus and nerve stretching from the radiation of the radiation, the main nerve of modern echinoderms, the Gang have, and most of the developed (except crinoids Gang). ② nervous system under the nerve inside the mouth, the mouth array with the same nerve. ③ back on the facial nerve within the nervous system or in the back on line under the skin surface, the relatively well developed in crinoids. Nervous system and blood system in the middle of water systems, more developed in the sea cucumbers and sea urchins. Starfish and the tail of a large cystic digestive stomach, intestine straight, bend; starfish often extend from the stomach to each wrist of a pair of blind sacs called pyloric gland. Outline of the digestive tract other than for a long, curved tube, even in the mesenteric abdominal body wall. Free anal tail and some starfish, can not digest all the things from the mouth spit it out. Crinoids of the mouth and anus all up, many crooked-shaped sea urchins often in the anus or mouth back body surfaces. No significant excretion organs, excretory function by the deformation of migratory cells are responsible for. Respiratory system is not well developed. Starfish and sea urchins in the gills of the skin around the mouth and gill area increase the ability to breathe. Some sea cucumbers have a special breathing organ, called respiratory tree. Echinoderms are mostly dioecious, male and female often no difference in appearance. Reproductive cells released into the sea in fertilization. Larvae occur in the same shape early, have cilia ring, the digestive tract is divided into three parts, thereafter vary with the outline, develop into four different types of larvae: ear-shaped larvae (sea cucumber), feather wrist larvae (starfish), sea urchin larvae and larval tail. Crinoids class larvae were barrel, known as the bottle-shaped larvae, and the New York floating gill bottles like the sea is very similar. Habits are important benthic echinoderms and distribution world's oceans. Vertical distribution of a wide range, from the intertidal to the Wan-meter-deep trench. They are mostly narrow-salt animals in brackish or salt water in the rare or occasional. No special coating in vitro, but has a special water system. Body of water can contain high and low salinity with the outside world and free of infiltration. Echinoderms of water pollution is very sensitive to contaminated water in the rarely seen them. Renewable power is generally very strong, if the wrist, disk or other external organs of the body damage or broken down, can be recycled. Some types are often self-cutting phenomenon. Few types of viable asexual reproduction bilharzia. Habitat for species. They crawl on the bottom or drill into the sand at the end of life. A small number of sea urchins and to the diamond. Crinoids class camp or temporary fixation fixation life. Planktonic life of a small number of sea cucumber line. Free-living species can be slow-moving. Feeding and diverse, and some of the swallowed, and some for the filter feeders, some carnivorous. Categories echinoderms have developed a body cavity and three in the mesoderm and endoderm from the inner skeleton, much more progress than the coelenterate. Adult echinoderms radial symmetry is due to the bilaterally symmetrical ancestors lived sessile and then get the secondary characters. Some of the more primitive traits still exist, such as advanced head and not the nerve center of primitive sensory organ, not the heart, vascular system is the sinus, respiratory relatively low, the delivery of nutrients and waste are excluded by the original amoeba cell the other. In the existing animals, not yet found a direct link with the groups of echinoderms. Bathurst (1900) imagined that the ancestors of echinoderms are bilaterally symmetrical, soft body, the symmetry of free-living larvae; Arthropoda - Insecta - animals under this definition. Their common features are: six-legged, no bones, the body surface of the crust by the support, into the eggs, larvae and adults of three growth stages, a multi-section body strong.
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Classification of porous phylum
Now there are about 10,000 kinds of sponges known, mainly based on the composition and shape of bone needles, divided into the following three key link. 1. Gang Calcarea calcareous sponges With calcareous spicules, are small, white, single groove type or ditch system Shuang'gou type. Normal habitat in shallow water areas. Such as white sticks sponge Leucosolenia, hair pot Grantia and so on. 2. Six put sponge Gang Hexactinellida Placed with six shaped siliceous spicules, of big, complex ditch ditch system type, flagella room large. Dwelling in the deep zone. Calamagrostis mediated Hyal0nema and long marriage as the same hole Euplectella. 3. Gang Demopongiae unusual sponge Placed with non-six-shaped siliceous spicules or sponge wire, ditch the Department re-groove type, flagella room is small, irregular shape. Habitat in fresh water or sea water. Habitat in the sea, such as Beihai wear cotton Cli0na, bath sponge Eusp0ngia; habitat in fresh water such as freshwater sponges Spongilla needles and so on. Medicinal species are mostly ordinary sponge Gang. Common, such as brittle needles sponge Sp0ngilla fragilis Lecidy, dials sponge Ephydatia mulleri var. Japonica (Higendorf) and so on.
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Porous animal
The original multi-cellular animals, sponges, also known as the phylum phylum (Spongiatia), commonly known as sponge (Sponge). Sponges are important reef, a few species have certain stratigraphic significance. Sponge raw animal tissues, no real digestive cavity and nervous system. Although the division of cells in sponges, but cooperate with each other even slightly, such as sponge ground screening, which separated the cells can survive for several days (the equivalent of protozoa). However, if no longer with each other, we can not continue to survive, sponges and cooperation that is independent of the characteristics that its structure remains cellular organism level, shows the original characteristics of multicellular animals. Sponges and more for the group, the monomer less. Body was symmetrical or asymmetrical radiation. Changes in the shape of a large group. Monomer for the pyramidal general, disk-shaped, goblet-shaped, spherical, etc. Size of the change from a few millimeters to 2m between. Most have calcium, silica, or horny skeleton. Sponges have spicules of bone (sponge-pin), sponge wire (bone wire) and non-mineral bone needle three. Spicules composed of calcium (calcite, aragonite) or silica (opal). Spicules can be divided according to the size of a large bone needle and a small bone needles. Horny sponge wire components of organic compounds, were filamentous, branching, or handover together. Silk sponge perishable, difficult to form fossils. Sponge's reproductive and sexual availability of two. In addition to the modern sponge sponge outline of a few common types are freshwater sponges, the majority of marine animals, benthic sessile camp. Sponge sponge and calcium modern rock scattered in shallow water areas, but the glass sponge inhabit a depth of 6000m in the deep ocean. Fossil sponges are also generally require similar water depth. Sponges often in a different geological age and layer foraminifera, bryozoans and algae together to form a reef.
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Important representative fossils
Composition and gutter system according to the type of bone can be divided into the following: Glass sponge Gang (Hyalospongea) Calcareous sponge Gang (Calcispongea) Hard sponge Gang (Sclerospongea) Coelenterate door features
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Radial symmetry
Coelenterate body has a fixed shape, and radial symmetry, that is, through the central axis of the body there are many facets of the body into symmetrical halves. Only the surface and back on the mouth side of the points. Some species are only two section through the central axis, the body is divided into equal halves, said two radial symmetry, such as sea anemones. This is between the radial symmetry and the symmetry between both sides of a form.
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Two germ layers and the original digestion chamber
Coelenterate is a real animal germ layers both inside and outside, between the two germ layers ectoderm cells from inside the middle lamella. The body cavity of the intestine that is original, has the function of extracellular digestion, the residue from the discharge port, it is also known to digest circulation chamber, or coelenterazine, coelenterate thus named.
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Cell and tissue differentiation
Coelenterate skin cells have differentiated into muscle cells, glandular cells, between cells, gill cells, sensory cells and so on. Skin-muscle cells are the cells within the ectoderm of the main executable epithelial and muscle physiology, it is called skin-muscle cells, which suggests that began with the primitive coelenterate epithelial and muscle tissue. Skin-muscle cells in the base of the extension of one or a few slender processes, including muscle fiber distribution, their composition and mechanism of contraction is similar to higher animals.
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Reticular nervous system
Began to appear from the coelenterate nervous system. Neurite to nerve cells linked to each other from a network, so called mesh nervous system. Nerve cells in the sensory cells within the ectoderm, skin-muscle cells connected to the outside world an effective response to various stimuli, but not the nerve center. Nerve conduction generally do not have a fixed direction, so the nervous system known as dispersion. Coelenterate not breathing and excretory organs, mainly rely on the cell surface to obtain oxygen from water and carbon dioxide and other waste directly into water or into the digestive cycle cavity from the discharge port.
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A hydra-based, two basic forms of jellyfish-type
Camp sessile polyp type, takes the shape of cylindrical, terminal, said base plate fixing the other end for the feeding of the mouth, surrounded by tentacles, in the thin layer. Gang of coral polyp type, the body wall ectoderm secrete calcareous exoskeleton. Floating jellyfish-type camp life, takes the shape of disc-shaped, prominent side, said outside the umbrella, under the umbrella, said concave side, the central suspension of a vertical pipe, tube end is the mouth, through the mouth into the digestive cavity and sub-loop The radiation tube branched, and has been connected through to the edge of the umbrella ring, the edge of the umbrella tube with tentacles and feel (balance capsule, tentacle sac). Hydromedusae umbrella from the next film around the edge to the central stretch, said border membrane.
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Reproductive method
Availability of reproductive and sexual reproduction two. Asexual budding often form groups. Mostly dioecious sexual reproduction, the polyp ectoderm formed by the outline of the gonad, but the key link Scyphozoa and the gonads of coral comes from the endoderm, between cells from the germ cells. Seafood species during embryonic development in planula stage. The main features of the door Platyhelminthes (A) bilaterally symmetrical animals began to appear from the flat side of a symmetrical body, through the animal's central axis, only one plane of symmetry (or that section) about the animals into two equal parts, so both sides are symmetrical called symmetrical. Evolution from the animal point of view, this was mainly due to animal body floating in the water of life from crawling into the bottom of life results. The development of this size has been the evolution of animals is important. Because all bilaterally symmetrical animals, the body can clear separation of front, left, dorsal. Body on the back of the development of protection functions, the development of a ventral movement functions, always the first contact with the forward end of the new external conditions, to promote the growing nervous system and sensory organs to the body of the front focus, the gradual emergence of the head, making the animals from the non-directional movement into directional movement, so that more accurate sensing of animals quickly and effectively, to adapt them to a wider range. Symmetrical on both sides is not only suitable for swimming, but for crawling. Possible evolutionary crawl from the water to crawl on land. So both sides of the symmetrical development of aquatic animal from the important to terrestrial conditions. (B) the mesoderm from the beginning Platyhelminthes, between the ectoderm and the inner embryo appeared in the embryo. Mesoderm of the emergence of animal structure and function of the further development of great significance. On the one hand because the formation of mesoderm reduced, the ectoderm of the burden, causing a series of tissues, organs, systems division, for the animals further complicated by a complete body structure provides the necessary material conditions to make up the organ systems Platyhelminthes level. On the other hand, due to the formation of mesoderm, and promoted to enhance metabolism. Such as Chinese and mesoderm formation of complex muscle layer, enhanced motor function, coupled with the bilaterally symmetrical body, the animal may be in the context of a larger intake of more food. And because the walls of the digestive tract has also been a muscle, the ability to make digestive tract motility also increased. These undoubtedly contributed to the strengthening of metabolic function due to enhanced metabolism, metabolic waste produced also increased, thus promoting the formation of the excretory system. Platyhelminthes start with the original drainage system - the original renal tubular system. Also, because the animals, motor function improved, regular contact with changing external environment, to promote the nervous system and sensory organs of further development. Platyhelminthes than the coelenterate nervous system has been significantly advances have begun to focus on the nervous system for the ladder. In addition, the Chinese and the real germ layers formed organizations store nutrients and water features, animals can withstand some degree of hunger and drought-resistant, therefore, mesoderm formation is the evolution of animals from the aquatic to the terrestrial one of the basic conditions . (C) the skin and muscle sac mesoderm formation as arising from a complex structure of muscle, circular muscle, longitudinal muscle, oblique. And the formation of epidermal ectoderm close to each other and the composition of the body wall called the "skin and muscle capsule", it formed a protective function in addition to muscular system, but also enhanced motor function, with bilaterally symmetrical, so that animals can be more faster and more effectively to food intake, more conducive to the animal's survival and development. In the skin-muscle within the capsule, the parenchyma of the filling, all the organs of the body are embedded in it. (D) is similar to the digestive system and general coelenterate, both through the mouth to the hole in vitro is the anus, only a single head planarian pharynx, such as single swallow insects (Haplopharynx) a temporary anus, so called imperfect digestive system. In addition to large intestine, no other body cavity. Intestinal endoderm by the formation of the blind tube, the type of business parasitic life, the digestive system tends to degradation (eg Trematoda) or completely disappear (Cestoda). (E) drainage system began to emerge from the Platyhelminthes renal tubular excretion of the original system. It exists in the door animals (other than non-intestinal target) of all taxa. The original tube from the kidney into the formation of the ectoderm on both sides of the body, usually with many branches of the excretory duct structure, a whole body vent outside. Most end of each small branch from the flame cell (flame cell) composed of blind tube. Actual flame from the cap cells and cells are composed of duct cells.
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Cap cells
(F) the nervous system of Platyhelminthes than the coelenterate nervous system has been significant progress. Expressed in nerve cells gradually move focus to form a "brain" and from the "brain" backward vertical separation of a number of longitudinal nerve cord in the nerve cord is connected between the horizontal nerve. In higher species, longitudinal nerve cord reduced, only one pair of ventral nerve cord development, which horizontal neural connections, such as trapezoidal (or ladder-type nervous system) has a brain and nerve cord nerve fibers in contact with body parts. Animals can be said that the original flat central nervous system. Nervous system, although this network coelenterate nervous system than advanced, but it is the original, because the brain would not focus exclusively on the "brain", but also scattered in the nerve cord. (Vii) the majority of hermaphrodite reproductive system, as the emergence of mesoderm, the formation of male and female germ cells have fixed some of the gonads and reproductive ducts, such as the fallopian tubes, vas deferens, as well as a series of subsidiary gland, such as the prostate gland and other egg yolk. This can pass to the germ cells in vitro, in vivo fertilization and mating line. Platyhelminthes camp life of free-living or parasitic, free-living species (such as the planarian Gang) located in the sea, fresh water or moist soil, carnivorous. Parasitic type of life (such as Trematoda and Cestoda) are parasitic on other animals, body surface or body, the intake of the animal nutrition. Echinodermata (Echinodermata) of the animal kingdom a body cavity of animals. Radial symmetry, a unique water system. Separation of body and digestive tract in the true body cavity, body wall are derived from the mesoderm within the bone, bilaterally symmetrical larvae, development through a complex metamorphosis. The mouth hole on the opposite side from the embryo occurs, is deuterostomes, the evolution of invertebrates in the high status. Include starfish, brittle stars, sea urchins, sea cucumbers and sea lilies, etc. (Figure 1). Because the epidermis is generally named after a spine. Full of seafood. Are about 5900 kinds of students, China has discovered 500. Look very different forms, there are star-shaped, spherical, cylindrical and flower. Release of radiation into the body of five symmetrical arrangement shown by the tube feet. According to whether the tube foot, the body is divided into a tube or step foot spoke with the Ministry and unregulated foot step between the spokes or indirectly with the Ministry. Internal organs, including the water system, nervous system, blood system and reproductive system are radial symmetry, except only the digestive tract. As the radial symmetry, body surface and back on the mouth side of the points. Although the doors of the outline shape are very different animals, but its basic structure is the same. Starfish and brittle stars was the star class, the upper and lower flat, the body axis is very short, flap side down, tube feet along the wrist (radial Department) for the radial arrangement. Sea urchins and sea cucumbers to extend the body axis, radial spokes between the Ministry and the Ministry of combination takes the shape of spherical or cylindrical, tube feet for radial order. Crinoids for the mouth, back on the mask for long-handled or attached to sticks with volume (Figure 1). Echinoderm skeleton is developed by a number of separate calcium carbonate composition of the bone plate, the plate by a single crystal of calcite. Bone outsourcing epidermis, the skin usually with spines. Sea urchins and starfish have different fork spine. The most advanced sea urchin skeleton, bone healing into the shell plate closely. Starfish, brittle stars and crinoids into the carpal plate-shaped vertebrae. Sea cucumber least developed bone, into tiny fragmented pieces of bone or bone needle. Echinoderm adult body cavity structure mainly occupied by digestive and reproductive systems, but crinoids body cavity filled with connective tissue membrane and cable. Water by the body cavity of the part - the water chamber evolved. Moving, feeding, breathing and feeling all rely on it to complete. Typical water pipe system from the sieve, through stone pipes, pass to the ring around the mouth of the Ministry of radial spokes and stretch tube. Radial branches assigned to a small tube tube feet. Tube feet are the base of the altar capsule, the end of a suction cup, filled with sea water, by stretching the muscles move the meter body. Nervous system, blood system and water system has a ring around the esophagus and radiation from the ring to each part of a main branch. There are three echinoderm nervous system: ① aperture, said outside the nervous system or nervous system in the epidermis or the epidermis, including the nerve ring around the esophagus and nerve stretching from the radiation of the radiation, the main nerve of modern echinoderms, the Gang have, and most of the developed (except crinoids Gang). ② nervous system under the nerve inside the mouth, the mouth array with the same nerve. ③ back on the facial nerve within the nervous system or in the back on line under the skin surface, the relatively well developed in crinoids. Nervous system and blood system in the middle of water systems, more developed in the sea cucumbers and sea urchins. Starfish and the tail of a large cystic digestive stomach, intestine straight, bend; starfish often extend from the stomach to each wrist of a pair of blind sacs called pyloric gland. Outline of the digestive tract other than for a long, curved tube, even in the mesenteric abdominal body wall. Free anal tail and some starfish, can not digest all the things from the mouth spit it out. Crinoids of the mouth and anus all up, many crooked-shaped sea urchins often in the anus or mouth back body surfaces. No significant excretion organs, excretory function by the deformation of migratory cells are responsible for. Respiratory system is not well developed. Starfish and sea urchins in the gills of the skin around the mouth and gill area increase the ability to breathe. Some sea cucumbers have a special breathing organ, called respiratory tree. Echinoderms are mostly dioecious, male and female often no difference in appearance. Reproductive cells released into the sea in fertilization. Larvae occur in the same shape early, have cilia ring, the digestive tract is divided into three parts, thereafter vary with the outline, develop into four different types of larvae: ear-shaped larvae (sea cucumber), feather wrist larvae (starfish), sea urchin larvae and larval tail. Crinoids class larvae were barrel, known as the bottle-shaped larvae, and the New York floating gill bottles like the sea is very similar. Habits are important benthic echinoderms and distribution world's oceans. Vertical distribution of a wide range, from the intertidal to the Wan-meter-deep trench. They are mostly narrow-salt animals in brackish or salt water in the rare or occasional. No special coating in vitro, but has a special water system. Body of water can contain high and low salinity with the outside world and free of infiltration. Echinoderms of water pollution is very sensitive to contaminated water in the rarely seen them. Renewable power is generally very strong, if the wrist, disk or other external organs of the body damage or broken down, can be recycled. Some types are often self-cutting phenomenon. Few types of viable asexual reproduction bilharzia. Habitat for species. They crawl on the bottom or drill into the sand at the end of life. A small number of sea urchins and to the diamond. Crinoids class camp or temporary fixation fixation life. Planktonic life of a small number of sea cucumber line. Free-living species can be slow-moving. Feeding and diverse, and some of the swallowed, and some for the filter feeders, some carnivorous. In addition to board tail, the echinoderms no parasitic species. Suction insects are parasitic on crinoids special class of polychaetes. A few snails feed on echinoderms, and some for external parasites, and some for internal parasites. Crustaceans and echinoderms are doing parasitic or symbiotic. Hidden fish (Figure 2) is well-known parasitic animals in the sea cucumber cloaca. There are parasitic in echinoderm body ciliate, flat worms and round worms. Categories echinoderms have developed a body cavity and three in the mesoderm and endoderm from the inner skeleton, much more progress than the coelenterate. Adult echinoderms radial symmetry is due to the bilaterally symmetrical ancestors lived sessile and then get the secondary characters. Some of the more primitive traits still exist, such as advanced head and not the nerve center of primitive sensory organ, not the heart, vascular system is the sinus, respiratory relatively low, the delivery of nutrients and waste are excluded by the original amoeba cell the other. In the existing animals, not yet found a direct link with the groups of echinoderms. Bathurst (1900) imagined that the ancestors of echinoderms are bilaterally symmetrical, soft body, the symmetry of free-living larvae; Arthropoda - Insecta - animals under this definition. Their common features are: six-legged, no bones, the body surface of the crust by the support, into the eggs, larvae and adults of three growth stages, a multi-section body strong.