Arthropods (millipedes)
arthropod
The largest class in the animal kingdom, arthropods, including more than one million invertebrates, account for almost 84% of all animal species. Members are diverse. Bilateral symmetrical invertebrates are covered with a part of chitin epidermis, which can fall off regularly. The epidermis is a protective device, which acts as an exoskeleton and provides an attachment surface for muscles. Muscle sequences are very complex, and some of them are specially used to manipulate flight and sound. The exoskeleton of the appendage has joints, so it is called arthropod. There are many special sensory organs; Body cavity degenerates and is replaced by blood cavity;
wolf spider
The nervous system consists of the back of the brain and a pair of abdominal nerve cords. More than 879,000 species have been recorded, of which about 86% are insects. It is estimated that there are more than ten thousand species of 10. Divided into four sub-doors:
Arthropod: an invertebrate with joints and shells, whose shells change with growth. The three main species are centipedes, millipedes, insects, spiders, subclasses and crustaceans. The ancestors of these three species were well developed during the CAMBRIAN period.
Arthropoda is the largest phylum in the animal kingdom, with the largest number of species, accounting for about 85% of all animal species. It has strong adaptability to the environment, and its living places include seawater, fresh water, mountains, air, soil, and even animals and plants at home and abroad.
Arthropod, also known as arthropod, is an animal whose body is composed of many links with different structures and functions. Usually it can be divided into three parts: head, chest and abdomen, but some kinds of chest and head are together, some kinds of chest and abdomen are not divided, and some kinds of whole body are healed, and chest and abdomen are not divided. Arthropods have a thick exoskeleton made of chitin on their body surface. Generally each node has a pair of points.
arthropod
An appendage of a joint, also called a joint. Joint movements are extremely flexible, mainly used for crawling and swimming. Arthropods are the largest species in the animal kingdom, accounting for 85% of the known animals, reaching more than 6,543,800+species, and the number of each species is amazing. Insects account for 80% of the total number of arthropods. Beetles account for 87% of insects, such as a bee colony, and the total number can reach more than 50 thousand. The diversity of body differentiation and body changes of arthropods makes them have strong adaptability, and arthropods can be found in almost any space on earth. Common centipedes, shrimps, crabs, spiders and various insects.
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Appearance characteristics
major feature
(1) Developed and thick exoskeleton
arthropod
(b) Effective respiratory organ-trachea
(3) The nervous system is developed
(D) the division of different laws and bodies.
(5) Segmented appendages
(6) Sensitive sensory organs
(7) There are chitin and protein's bones in vitro.
Division of the body
Some are split and trunk; Some are divided into three parts: chest and abdomen; Some are divided into chest (precursor) and abdomen (afterbody). Some somites have merged during embryonic development. The exoskeleton covering the head and chest is called the carapace. The appendages arranged in a straight line are called single limb type, and the bifurcated ones are called double limb type. Appendages are used for swimming, walking, breathing and reproduction, or as sensory organs and mouthparts; Spider spinneret is also composed of abdominal appendages. Unlike the wings of other animals (birds, bats, pterodactyls, flying frogs and flying fish), the wings of insects evolved from limbs. Many insects have two pairs of wings and can move like a pair of wings. Some groups have bristles or leaves connecting the front and rear wings on each side. Some insects have a pair of wings that are not used for flying. For example, the hind wing of Diptera degenerates into a balance bar, which has many sensors to control flight.
arthropod
Most arthropods are hermaphroditic. The location of the genital foramen is different: centipedes and insects are near the back of the body, crustaceans are at the back of the chest, Ma Lu, candle and heald are near the head, and arachnids are near the middle of the body. Sperm is usually passed to females in sperm pods. In the simplest case, the sperm pod of arachnids, such as spiders, arthropods and some mites, is a sticky sperm mass, and the male transmits the sperm pod by means of appendages (claws, limbs or feet). The sperm pods of scorpions, pseudo scorpions, scorpions without whips, scorpions with whips, spiders with split shields and some mites are complex and rod-shaped. During mating, there is a wedding dance. The male fixes the sperm pod on the ground, takes the female to the place where the sperm pod is placed, and lets the sperm enter the female reproductive hole. Spiders are transported by physical contacts; The changes of tarsal joint and posterior tarsal joint of the third gait of arthropods also play the same role. There are also parthenogenesis, viviparous or polyembryonic reproduction (a fertilized egg forms several embryos).
arthropod
Most crustaceans and many polypods have fewer somatic cells than adults. On the contrary, during embryonic development, many chelates form many knots. Some groups develop directly, some hatch as larvae, and the larvae of different groups are different. Hormones control the change, growth, molting, metamorphosis and development of body color. Some have poisonous glands, which are used for predation and digestion. In some membrane wings, poisonous glands are connected with ovipositors or stingers; The venom glands of larvae are connected with thorns or bristles. Some glands produce unpleasant smells. In addition to monocular or compound eyes, there are tactile hairs, or senses of smell, taste, hearing and internal stimuli, as well as humidity and temperature. There are bell-shaped receptors near the wings of insects, which are used to measure epidermal tension. The harp on the spider's foot can feel the vibration of the net, which distinguishes the male spider from the prey struggling on the net. Arthropods and polychaetes have many similarities, and it is generally believed that these two species evolved from the same ancestor.
There are many kinds of arthropods, ranging from deep sea to mountains, and some even have flying wings. It is the only invertebrate that really adapts to life on land. At present, there are more than 6.5438+0.2 million known arthropod species, accounting for about 84% of the total known in the animal kingdom. Common species are aquatic arthropods such as shrimps and crabs, and terrestrial species such as spiders, centipedes and insects.
arthropod
Arthropods are long, flat segmented animals that feed on carrion, and each segment has two feet. It evolved in Silurian, and about 10000 species are still alive today. Arthropods and centipedes are well known multi-legged arthropods.
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Growth distribution
Arthropods are common in land, sea and fresh water. Small and medium-sized crustaceans in seawater are the main components of zooplankton and the food of other invertebrates, fish and whales. Insects are dominant on land and have important economic significance as pests or pollinating crops. Spiders, mites,
arthropod
Scorpions and other arachnids also live on land. Despite the development of effective pesticides, insects and mites still threaten the lives of people and animals all over the world. Spread malaria, yellow fever, rickettsia, plague, filariasis, etc. And destroy grain, wood and food. Many-legged animals live in wet places, which has little economic significance.
The hard exoskeleton of arthropods affects the size of their bodies. Only aquatic species can grow bigger because water can support part of their weight. For example, the extinct platypus is 1.8 meters long, while the existing crustaceans are even larger. Cancer can weigh up to 6.4 kilograms, and the distance between the two pliers is 3.8 meters. The high calcification of crustacean shells makes the body heavier, which is beneficial to the life of benthos. There are few terrestrial species: the largest insects and spiders do not exceed100g; The smallest are some parasitic bees and mites, with a body length of less than 0.25 mm. Although the structure is complex, it weighs less than the nucleus of a large cell. The deep-sea crab (Ethusina abyssicola) exists at a depth of more than 4,000 meters, while the jumping insects (collembola) and jumping spiders (spiders) live at a height of more than 6,700 meters on Mount Everest. Collembola and oribatid mites can settle in Antarctica. Many arthropods are parasites inside and outside the body.
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Specific classification
The existing arthropods, except the extinct Trilobinae, are traditionally divided into two subfamilies according to the presence or absence of tentacles. Cladocera without tentacles, named after 1 appendages are edible claws, including horseshoe crabs, scorpions, spiders, mites and so on. The tentacle is called Palatina, and its 1 counterpart is jaw, including Insecta, Crustacea, Scolopendra and Ma Lu. But now most zoologists think that the subphylum of jawed animals
arthropod
It is an artificial combination, and there is no blood relationship between the groups involved. Therefore, arthropods should be divided into four subfamilies: extinct trilobites, extant crustaceans, crustaceans and monotremes. Trifolium subfamily shows the most primitive characteristics, all living in the ocean. Except the antenna, other body parts have two branch appendages. Head appendages of arthropods and arachnids. Book gill and book lung are homologous, indicating that the two types are relatively close. In the past, crustacea, as a class, was considered to be homologous to Polypoda and Insecta because of its jaws, but crustacea had two pairs of antennae and nauplii, which were not found in other phyla, so it should have originated independently. Different from the subfamily that originated in the sea, the suborder Monopoda seems to have evolved from land, with tentacles and jaws, and its appendages are basically single-branched, hence its name.
Arthropoda has 5 subfamilies and 20 classes as follows:
Protoarthropod phylum
Prototracheae
subphylum trilobitomorpha
Trilobite (trilobite)
Chelidonium subphylum
Valvulales (Valvulales)
arthropod
arachnid
Marine spider
Crustacea subfamily
cephalopods
Branchiopod (branchiopod)
Xiaomi encyclopedia (Xiaomi encyclopedia)
Ostracoda (Ostracoda)
Mitacarida (Mitacarida)
Micro-contraction (tanturocarida)
copepod
Branchlets (branchials)
Rolling door; Manpoda
Soft beetle (soft beetle)
Monogamy subphylum
insecta
Biped phylum
Liposome a
Paul Boda (Candle Boda)
Comprehensive outline
Trilobite fossils
subphylum trilobitomorpha
Trilobite, Trilobite, was dominant in the early Paleozoic ocean about 570 million years ago and extinct in Permian 280 million years ago. The body is oval with a flat back and abdomen, which is divided into three parts: head, chest and tail. Divide vertically into three leaves. 3.5 ~ 75 cm long.
One-limb subphylum
Uniramia's head has tentacles, a big jaw and a small jaw. One or two limbs connected to the chest. Part of the abdomen is inseparable from the chest and has appendages; Or separate from the chest, with or without attachments. (1) Candeira Tower: A tiny multi-legged animal. Two pairs of appendages become mouthparts, 8 ~
Single limb subphylum structure
1 1 footstep. The antenna is a 4-node (rarely 6-node), terminal branch and multi-node whip antenna. The maximum body length is1.9mm. (2) Biped animal: a long and narrow multi-legged animal, whose abdomen consists of two sections, each with two pairs of feet and air holes. The head has a large upper jaw; Small palate synthesizes palatal lip; Sometimes there is an eye; The antenna is short and hammer-shaped; The chest has four single segments, and the genital foramen is in the third segment. Body length is 0.3 ~ 28 cm. (3) Lipopod: a long and narrow multi-legged animal with many obvious abdominal segments, each with a pair of feet, and the appendage of the first abdominal segment becomes a poisonous palate; The genital foramen is at the distal end. The body length is about 0.5 ~ 26.5 cm. (4) Anpoda: a small multi-legged animal with three pairs of mouthparts, 12 pairs of walking feet and a pair of dorsal rotators. The genital foramen is in the fourth trunk segment. Collembola with a maximum body length of 8 mm (5): a small arthropod resembling an insect, widely distributed. Extraoral palatal type; The antenna is usually 4 nodes; Simple eyes; Three chest segments have feet; Six abdominal segments with bifurcated elastic devices; Usually there is no trachea; Marcello Malpighi's tubule. The maximum body length is 5 mm (6) Insecta: three pairs of appendages form mouthparts; The head is composed of six sections, with a pair of antennae, often with side eyes and middle eyes; The chest has three sections, each with a pair of feet, and some have wings in the second and third sections; The abdomen consists of 1 1 segment, and there are no appendages in adults. The genital hole is in the back. Body length is 0.25 mm to 33 cm.
crustacean
Crustacea, mostly; Gill respiration; The exoskeleton is strong; With tentacles and jaws.
Chelating subphylum
Chelicera, there are no tentacles in the front, but there are.
Sea spider picture
Shaped claws and tentacles (or feet); There is a one-legged gait in the chest; Abdominal appendages are highly specialized. (1) Merostomata: a large marine species with gillbooks precursors completely covered by crustaceans; There is a long thorn on the back of the body. (2) Arachnoidea: The front and the back are connected by a narrow abdominal stalk, or the two parts are healed. The front part is provided with claw limbs, contact limbs and four pairs of walking feet; The afterbody usually has no appendages. Breathe through the lung book, trachea (or both), and the opening is behind the body. The genital foramen is located on the ventral surface of the second segment of the posterior body. Body length is 0.25mm to 18cm. (3) pycnogonida [pantopoda]: seafood; The head has a tubular kiss and three pairs of appendages; The chest is very narrow and consists of four sections, each with a pair of feet; Small abdominal tumor; There is no respirator or body excretor. The body length is 0.2 ~ 6 cm. The shape of crustaceans varies greatly. The smallest crustacean, such as Daphnia, is less than 1 mm in length. The largest giant crayfish, the width of which can reach 4 meters when its claws are extended. The body is long and cylindrical with distinct segments, which are all divided into three parts: chest and abdomen. The head consists of six joints. Section 1 has no appendages, and other sections have 1 appendages (there are two pairs of antennae in front of the mouth, and 1 pair of jaws and two pairs of jaws behind the mouth). The cephalic and thoracic segments often heal, which is called cephalic and thoracic segments. Shrimp, such as Decapoda, Kryptonidae, Myxocara, etc. A carapace is produced from the rear edge of the head, covering all or part of the head and chest. Some groups are bivalve shells.
arthropod
(Ostracoda, Ostracoda), covering the whole body and appendages; Some of them are fleshy, and the outer surface is reinforced with shell plates (such as Tenpoda). Many crustaceans only use 1 or 1 and 2 thoracic segments to heal (for example, copepods, isopods, amphipods, etc. ). Lower crustaceans have no obvious boundary between chest and abdomen, and are collectively called trunks (such as branchiopods). The number of body segments of higher crustaceans-molluscs is basically fixed, with 8 segments in the chest (each segment 1 appendage pair), 6-7 segments in the abdomen, plus 1 appendage-free tail segment, and 6 pairs of appendages in other abdominal segments (except Phyllanthus urinaria, 8 segments in the abdomen and tail fork 1 appendage pair). Except mollusks, other types of abdomen have no appendages, but the distal segment has 1 caudal fork. The number of trunk limbs varies greatly, from 2 pairs (Ostracoda) to more than 60 pairs (Brachiopoda-horseshoe crab).
other
Arthropods with uncertain genetic relationship include crustaceans, Tardigrada and pentaphylum.
Arthropods have hard bodies and exoskeletons.
A segmented body and jointed feet.
They walk on eight feet. Spiders and scorpions
The son also belongs to this door.