Biological topic

Definition: A complete single-celled organism that can live independently.

Red tide: some kinds of flagellates, such as cordate telosma and Trichinella spiralis. Excessive reproduction will lead to discoloration of large areas of seawater. It caused serious hypoxia in the water and caused a large number of deaths of fish, shrimp and shellfish.

Phagocytosis: animals such as amoeba have no mouths. When the temporary front end touches the fifteenth, it sticks out its prosthetic foot to defend it from all directions and wraps the group food particles into cells. This way of eating is called phagocytosis.

Vacuolation: the phenomenon that single cells such as amoeba rely on the temporary front end of the body to eat liquid food like drinking water.

Intracellular digestion: When single-celled animals eat, they will bring some water with the food and form food vacuoles. Food vacuoles fuse with lysosomes, and food is digested by various hydrolases contained in lysosomes. The whole digestion process is completed in cells, which is called intracellular digestion. Some cells of some multicellular animals can also ingest food for intracellular digestion.

* * * Habitat: Two animals that can live independently live together in a certain relationship and do no harm to alien animals.

* * * Health: Two animals live together or one animal lives in the other animal, which depends on each other and benefits each other.

Nutritive layer: the stage when parasitic protozoa take nutrition and can take the initiative to take nutrition, and grow and reproduce is the pathogenic stage of parasitism.

Schizogamy: After the spores entering the host cell mature from the trophozoite, they first divide into multiple nuclei, which is called schizogamy, and then the cytoplasm divides with the nuclei and wraps each nucleus to form multiple schizogamy, which is called schizogamy.

Spore reproduction: after the sporozoites entering the final host develop into oocysts, the nucleus and cytoplasm divide many times, and at first, multiple spore mother cells are formed, each spore mother cell forms multiple spores, and one spore can form multiple spores.

Conjugate reproduction: the unique sexual reproduction mode of paramecium and ciliate. Conjugate reproduction refers to the adhesion of the oral groove parts of two paramecium, and the surface membrane of this part gradually dissolves and the cytoplasm is connected with each other. This process is equivalent to fertilization. After that, the two paramecium bodies separated and divided to form four new paramecium bodies.

Spiny filament vesicles: Some small rod-like structures arranged perpendicular to the surface membrane under paramecium. When stimulated, they release organelles with defensive functions.

Stress: Single-celled protozoa have no nervous system, but they can still respond to external stimuli.

The main characteristics of protozoa:

1. The body consists of only one cell.

2. Various physiological activities are completed by various organelles.

3. There are three kinds of nutrition: plant nutrition (autotrophic, photosynthetic nutrition), animal nutrition (heterotrophic, phagocytic heterotrophic) and saprophytic nutrition (osmotic nutrition).

4. Breathing and excretion mainly depend on the osmosis of cell membrane, and the function of contraction vacuole is mainly to regulate water balance, and parasites perform anaerobic breathing.

5. The digestion mode is intracellular digestion.

6. There are various ways of reproduction, and spore reproduction, schizont reproduction and paramecium joint reproduction of spores are unique to protozoa.

irritability

8. It can form cysts and survive in harsh environment.

Characteristics of flagellates

1. Use flagella as power

2. It has three nutrition modes of protozoa. In addition, euglena can do both photosynthetic nutrition and osmotic nutrition, so it is called mixed nutrition.

3. Reproductive methods can be divided into two categories: asexual reproduction and sexual reproduction. Binary division and budding propagation are special ways of asexual reproduction.

4. It can form cysts and survive in harsh environment. (Green eye worm, Leishmania, Trypanosoma, Cryptosporidium branchiatus)

Characteristics of peach

1. Pseudopoda with motor and feeding functions

2. Some species have shells.

Step 3 devour nutrition

4. Breathing and excretion mainly depend on the osmosis of the body surface, and binary division and reproduction are common, and cyst formation is extremely common (amoeba, amebic dysentery).

Spore characteristics

1. Lack of any exercise equipment (some species can do deformation exercise or have flagella at some time in their lives).

2. The whole camp is parasitic, generally lacking feeding organelles, and getting nutrition by body surface infiltration.

3. Schizomorphs all have apical recombination structure, which is related to the invasion of host cells by worms.

4. Complex life history, strong reproductive ability and generational alternation. Generally speaking, life history goes through three stages: fission reproduction, gamete reproduction and spore reproduction. Among them, fission and spore reproduction can breed a large number of offspring, and spore reproduction is unique to this kind of plasmodium vivax.

Characteristics of ciliates

1. Use cilia as motor organs.

2. The nucleus and cytoplasm are highly differentiated, and the nucleus is divided into large and small nuclei, the small nucleus is related to reproduction, and the large nucleus is responsible for nutrition; Cytoplasm differentiates into many organelles, such as cell orifice, cell pharynx, cell anus, contraction vacuole and echinochloa, which are unique to paramecium.

3. There are special sexual reproduction modes, namely zygotic reproduction and asexual horizontal binary division.

4. Strong irritability

5. Get through the harsh environment with cysts

Metazoa: Compared with the name of protozoa, most multicellular animals are called metazoa.

Metazoa: an intermediate animal between protozoa and metazoa, with a long parasitic history and the characteristics of protozoa and metazoa.

Protozoa: An animal whose protozoa directly or indirectly become the animal's mouth after the embryonic stage. (Flat, connected, joined)

Metastoma: An animal (Echinoderm, Hemiptera, Chordata) whose mouth is closed or becomes an animal's anus, and whose mouth is re-formed at the end opposite to the original mouth.

Sponge phylum

This is a form of sponge to weather bad weather and environment. When the environment is bad, the degenerated cells of sponge mesoderm gather in piles and secrete a layer of horny membrane outside. At the same time, some acicular cells secrete many double-headed or short columnar acicular bodies on the keratinocyte membrane, forming embryos. Once the environment is suitable, new individuals will form.

Groove system is a unique structure of sponges, which is of great significance to their lives. Gully system is the channel of water flow, and the physiological functions of sponge such as feeding, breathing and excretion are maintained by the passage of water flow.

Central cavity: refers to the central cavity of sponges, also known as sponge cavity. It is only a channel for water flow and has no digestive function. Food is digested by the collar cells on the wall of the central cavity, so the central cavity is also called pseudo-gastric cavity.

Dicystic larva: After the fertilized egg of sponge cleaves to form blastocyst, the tiny cell of animal pole produces flagella and enters the cavity of blastocyst, and an opening is formed in the middle of the big cell at the other end. Later, the small cells of the blastocyst turned out from the opening, and the flagellated side of the small cells inside turned over the surface of the blastocyst, so that one end of the animal pole was a small divided ball with flagella, and the other end of the plant pole was a large divided ball without flagella. At this point, it looks like two cysts in appearance.

Why are sponges called the most primitive and lowest multicellular animals?

1. Sponges are diverse in shape, and most of them have no certain symmetrical form, and their lives are fixed.

2. There is no obvious differentiation of tissues and organs, no intracellular digestion of digestive system, no slow response of nervous system, only the formation of germ cells and no reproductive system.

3. The skeleton formed by spicules in mesothelium is the basis of sponge classification.

Having a special drainage system is a good adaptation to a fixed life.

5. The reproductive mode is simple. The formation of germ is a special asexual reproductive mode of sponge, and fertilization is completed in mesothelium.

6. Strong regeneration ability

Sponge is a branch of animal phylogenetic tree.

Sponge animals have very primitive morphological structure and physiological function, with special structures such as collar cells, bone needles and aqueduct system, and there is a phenomenon of germ layer reversal during embryonic development. Zoologists have long recognized that it is a branch of the evolutionary tree of animals, and other multicellular animals did not evolve from sponges.

coelenterata

Radiation symmetry: the body can be divided into two equal parts through many sections on the central axis of the body, which is a primitive form of low-level symmetry, such as most coelenterates.

Double radial symmetry: Only when two sections pass through the central axis of the body can the body be divided into two equal parts, which is an intermediate form between radial symmetry and bilateral symmetry.

Bud propagation: after the mother matures, buds are produced by budding to form new individuals, such as the asexual propagation of hydra.

Digestive cavity and circulatory cavity: a cavity in the body surrounded by endodermal cells of coelenterates. This digestive cavity has both digestive function and circulatory function.

Dermal muscle cells: There is no original structure between the epithelium and muscle of coelenterates, and epithelial muscle cells belong to both epithelium and muscle.

Mesothelium: A thin, transparent gelatinous substance located between two germ layers of coelenterate body wall and secreted by endodermal cells that support the body.

Floating larva: a swimming larva whose gastrula is formed by fertilized eggs in the life history of coelenterates and has cilia on the surface.

Regeneration: the phenomenon that the original structure can still grow through cell dedifferentiation and redifferentiation after removing a part of the mother.

Spine cell: It is unique to coelenterates. Each stinging cell has a nucleus located on one side of the cell and a sac-shaped stinging silk sac, which stores venom and coiled filament tubes, playing a role in predation and defense, such as hydra.

Extracellular digestion: gland cells secrete digestive enzymes and enter the digestive cavity to digest food.

The fertilized eggs of Hydra undergo complete cleavage to form solid gastrula, which is indirect development.

Why is the digestive circulation cavity of coelenterate different from the central cavity of sponge?

The central cavity of sponge is an integral part of the ditch system, and it is also the cavity through which water flows. The digestive circulation cavity of coelenterates has a digestive function, which can be used for extracellular and intracellular digestion, and has a circulatory function, which can transport digested nutrients to all parts of the body. It is a cavity surrounded by endoderm, that is, the gastrula cavity in embryonic development.

Compare the similarities and differences of coelenterates.

* * * Similarity: radial symmetry or two radial symmetry, with two germ layers, tissue differentiation, digestive circulation cavity and reticular nervous system, composed of stinging cells.

Difference: Hydrozoa are hydra type and jellyfish type, that is, the phenomenon of generation alternation. Hydra is a small jellyfish with a doomed membrane, its sensory organ is a balance sac, and its gonad is derived from ectoderm. Jellyfish is a well-developed jellyfish type, which degenerates into hydra and often appears in the form of larvae. Generally, it is a large jellyfish with no membrane, and its sensory organ is a tentacle sac with complex structure. There are gastric filaments in the gastric sac, and the gonads are derived from endoderm. Coralline algae is only a hydra, and its structure is complex, including oral tube, oral trench, diaphragm and diaphragm filament. The gonad is derived from endoderm.

The position and function of coelenterates in the process of animal evolution

Coelenterates have some basic characteristics that sponges have not yet appeared but other multicellular animals have.

1. In the process of animal evolution, the germ layer differentiation of coelenterates first appeared.

2. Organized differentiation.

3. Digestive cavity, namely digestive circulation cavity, began to appear.

4. Coelenterates have a fixed symmetrical system, that is, radiation symmetry, so it can be said that coelenterates are the most primitive metazoans and the starting point of other higher multicellular animals.

flatworm

Bilateral symmetry: only one plane of symmetry divides the animal body into two equal parts through the central axis of the animal body, also known as left-right symmetry, which is an important adaptation for the development of animals from aquatic to terrestrial.

Prorenal excretory system: It is composed of excretory ducts, capillaries and flame cells, originated from ectoderm and branched many times along the way. Many branches are interconnected into a network, and there are tube cells at the end of each branch, and cap cells are attached to them to form flame cells together. The primary function of the renal excretory system is to regulate the osmotic pressure of water and eliminate some metabolic wastes.

Flame cell: the basic unit of the primary excretory system, consisting of tubular cells and cap cells. It is a hollow cell, with a bunch of cilia in the cell, which constantly swings evenly. Through the permeation of cell membrane, the water, liquid and waste in it are collected and sent out of the body through the collection tube, drainage tube and drainage hole.

The Significance of Left-right Symmetry and Three-germ Layer in Animal Evolution

The appearance of left-right symmetry urges the animal's body to be clearly divided into front, back, left, right, back and abdomen. The back is mainly responsible for protection, and the abdomen is responsible for crawling and foraging. Because the front end often comes into contact with external conditions first, the nervous system and senses converge to the front end, and the head gradually appears, which enables animals to do directional movements and take the initiative to take food, making their adaptation range wider and creating conditions for animals to develop from aquatic to terrestrial. The appearance of mesoderm is of great significance to the further development of animal structure and function. On the one hand, the formation of mesoderm lightens the burden of endoderm, especially the burden of motor function, and causes the differentiation of a series of organs, which provides conditions for the further complexity and integrity of animal structure and makes flat animals reach the level of organ system; On the other hand, due to the formation of mesoderm, it promotes the strengthening of metabolism. For example, the complexity of muscles enhances the motor function, and the feeding range is wider. The strengthening of exercise also promotes the development of the nervous system; The appearance of mesoderm is the basic condition for animals from aquatic to terrestrial.

Development stage of trematode: egg-metacercaria-metacercaria-cercaria-cercaria-metacercaria.

Primitive cell tumor

Prosthetic cavity: also known as secondary cavity or primary cavity, located between the body wall and digestive tract of nematodes and other animals. It is not covered by the body cavity membrane formed by mesoderm, but only the body wall mesoderm without the intestinal wall mesoderm, which is formed by the development of blastocyst cavity in embryonic stage.

Complete digestive tract: a well-developed digestive tract, that is, a mouth with anus, such as the digestive tract of nematodes, where fresh food enters through the mouth and the residue is discharged through the anus after digestion.

Characteristics of protozoa

Prosthetic cavity animals have protocorms between the body wall and digestive tract, and have perfect digestive tract, namely mouth and anus; There are glandular and tubular excretory ducts, which belong to protorenal type, with horny membrane on the body surface, bisexual and simple nervous system.

An important stage of embryonic development

Fertilized egg-cleavage-blastocyst-gastrula-formation of mesoderm and body cavity-differentiation of germ layer

Protozoa form mesoderm and body cavity by terminal cell method (cavity division method)

annelida

1, rhythmic segmentation: the body is composed of many body segments with similar shapes, which is called segmentation phenomenon. Body segments are separated from each other by diaphragm in the body, and corresponding internode grooves are formed on the body surface, and many internal organs such as circulation, excretion and nerves are also arranged according to body segments. Except for the first two segments and the last segment, the other segments of annelids are basically the same in shape, which is called synrhythmic segment.

2. Secondary body cavity: the true body cavity. There is a wide cavity between the body wall and digestive tract of annelids, that is, the secondary cavity, which is formed by mesoderm cells in the early embryonic development, then divides into cavities and gradually develops and expands. Its endoderm adheres to endoderm, differentiates into muscular layer and visceral membrane, and forms intestinal wall with intestinal epithelium; Lateral mesoderm is attached to the inner surface of ectoderm, which differentiates into muscular layer and parietal membrane, and forms body wall with mammary epithelium. The secondary body cavity is covered by mesoderm and has the epithelium or tunica coeloma.

3. Closed-tube circulation: It is a perfect circulation system with complex structure, consisting of longitudinal blood vessels, annular blood vessels and their branches. Blood vessels are connected by microvascular network, and blood always flows in the blood vessels without flowing into the gaps between tissues, forming a closed circulatory system. Blood flows in a certain direction at a constant flow rate, which improves the functions of transporting nutrition and carrying oxygen. Earthworms belong to this system.

4. Posterior renal duct: The typical posterior renal duct is a tortuous tube, one end of which is opened in the anterior body cavity, called renal foramen, and there is a funnel with fibers; The other end is open on the body surface of the body segment, which is the renal foramen. The posterior renal duct not only excretes metabolites in the body cavity, but also excretes metabolites and excess water in the blood because of the dense capillaries on the renal duct. Such as annelids and fleas.

5. Chain nervous system: This nervous system is centralized. There is a pair of brains synthesized by the superior pharyngeal ganglion at the back of the pharynx at the front of the body, and the left and right sides are connected by a pair of peripheral pharyngeal nerves and a pair of healed hypopharyngeal ganglia. Since then, the abdominal nerve chain extending backward is formed by the confluence of two longitudinal abdominal nerves, and each segment forms a ganglion, which looks like a chain as a whole, so it is called a chain nerve. The brain can control the movement and sensation of the whole body, and the abdominal nerves send nerves to the body walls and organs, which plays a reflective role. Earthworms have this nervous system.

6. The trochanter: The individual development of marine annelids has the trochanter stage. The larvae are gyro-shaped, with a bunch of cilia at the top of the front end of the body, which has sensory function, and sensory plates and eye points at the base; There are two ciliated rings in the middle of the body, and the body is not segmented. The protonephric duct, protoglomerulus, nerve and epithelium are connected, which is very different from the adult morphology and internal structure. The growth period and its metamorphosis are of great significance in animal evolution. Such as annelids and fleas have this larval stage.

7. Body surface respiration (skin respiration): Oxygen in the air first dissolves in the wet membrane on the body surface, then penetrates into the cuticle membrane and epithelium, reaches the microvascular plexus, and is transported to various tissues of the body through blood circulation. The carbon dioxide produced by breathing is the opposite of the above. Carbon dioxide is transported to the body wall through blood vessels, then diffused to the body surface and discharged into the air. This kind of breathing through the body surface is called skin breathing. The annelid earthworm belongs to this way of breathing.

8. The main characteristics of annelids are: 65,438+0) body segmentation, mainly rhythm segmentation; 2) Mycosis, with many closed circulatory systems, some body cavities degenerate into blood sinuses (open), and the excretory organ is the posterior renal duct; 3) Many bristles, some with warty feet; 4) Chain nervous system, the sensory organs of free-living species are developed, and the sensory organs of burrowing species are degraded. Most marine species have trochophore stage.

Because of the above characteristics, annelids have developed to the advanced stage of animal evolution, which is the beginning of higher invertebrates. In particular, the somite is the foundation of animal development. With bristles and warty feet, it makes the movement agile and secondary body cavities appear, which correspondingly promotes the occurrence of circulatory system and posterior renal duct, thus making various organ systems more complicated and enhancing their functions. Nerve tissue is further concentrated, forming brain and abdominal nerve chains, forming a chain-like nervous system, with developed senses, sensitivity to stimuli and rapid response. This can better adapt to the environment and develop to a higher stage.

9. Significance of the appearance of soma and secondary body cavity in animal evolution: many internal organs such as soma, soma in vitro and soma in vivo, circulation, excretion, nerves, etc. also show the phenomenon of repeated arrangement according to soma, which not only enhances motor function, but also plays an important role in promoting animal metabolism and enhancing adaptability to the environment, and is also the beginning of physiological division of labor. Therefore, segmentation is an extremely important symbol in the evolution of invertebrates. The appearance of secondary body cavity is an important development of animal structure. There are muscles in the digestive wall, which can enhance peristalsis and improve digestive function. At the same time, the digestive tract is separated from the body wall by the secondary body cavity, which promotes the occurrence of organs such as circulation and excretion, further complicates the animal body structure and improves various functions. The wall of the secondary body of annelids is filled with body cavity fluid, which flows in the body cavity, which can not only assist the transportation of substances, but also is closely related to the expansion and contraction of the body segment.

Molluscs

1. Shells: Shells are one of the main characteristics of mollusks, so mollusks are also called shells. Shells are secreted by epithelial cells of the mantle, and the main components are calcium carbonate and a small amount of shell matrix (or shellfish elements). Generally, the shell structure can be divided into three layers from outside to inside, namely stratum corneum, prismatic layer and nacre. Most mollusks have 1-2 or 8 shells with different shapes, mainly to protect their soft bodies.

2, the mantle: the skin folds on the back of the body extend downward, often wrapping the entire visceral mass, forming an mantle. The mantle consists of two layers of epithelium and connective tissue in the middle. The secretion of the outer epithelium forms a shell, and the cilia of the inner epithelial cells swing, forming a water flow through the water inlet to complete breathing, feeding, excretion and reproduction. In addition, the mantle also has the functions of protecting internal organs, helping exercise (such as cephalopods) and breathing (such as snails).

3. Pericardial cavity: that is, the remaining part of the secondary body cavity of mollusks, with a heart inside and a pericardial cavity membrane outside, which is generally located at the back side of the visceral mass.

4. Tongue teeth: Tongue teeth are unique organs of mollusks (except flap gills). They are located on the tongue-shaped protrusions at the bottom of the mouth and consist of rows of horny teeth, which are file-like. When eating, due to muscle contraction, tongue and teeth can move back and forth to file and scrape food. The number, size and shape of tongue teeth are one of the important characteristics of species identification.

5. The main characteristics of mollusks are: 1) Soft body, mostly bilateral symmetry, consisting of three parts: body, feet and visceral mass. Most of them have shells secreted by the mantle (1-2 or 8, a few have no shells or disappear), so this door is also called shell. 2) The foot is a moving organ, and the foot of cephalopod becomes the wrist and funnel. 3) The digestive system is U-shaped with digestive glands, and there are jaws and tongue teeth in the mouth except flap gills. 4) Aquatic species breathe through gills, while terrestrial species have "lungs". 5) Open-tube circulatory system (except Cephalopods, which is closed-tube circulatory system), the heart is in the perivascular cavity, usually with one ventricle and two ears (Gastropoda has only one ventricle and one ear). 6) The renal excretory system usually has a pair of kidneys (Gastropoda has only one kidney due to torsion). 7) The nervous system generally has four pairs of ganglia (brain, side, foot and viscera) and nerve cords connecting them. 8) Most species are bisexual, and a few are bisexual, ovoid or viviparous. Indirectly developed marine species include trochophore and disk larvae, mussels have one larva, and cephalopods develop directly.

Echinoderm phylum

1, five radiation symmetry: the central axis of the mouth surface and the mouth surface of the insect body can make five different incisions on the body, and the two parts of the incision are basically symmetrical with each other, or the whole body is composed of five similar parts along the body axis.

2. Secondary radiation symmetry: Echinoderm is symmetrical on both sides in larval stage, and becomes five radiation symmetry when it grows into an adult. We call this radiation pair secondary radiation symmetry.

3. Water pipe system: It is a unique structure of echinoderms, evolved from a part of body cavity, and its main function is movement.

4. Perivascular system: The blood system of starfish is very underdeveloped, which consists of tiny pipes or blood sinuses, which are often surrounded by corresponding tubular body cavities (usually called perivascular sinuses). This cannula cavity is the perivascular system.

5. The main characteristics of echinoderms: 1) Echinoderms are different from other groups of invertebrates, and they are metazoans. 2) Secondary radiation symmetry, but five radiation symmetry is dominant, and the larvae are bilateral symmetry. 3) Endoskeleton originated from mesoderm often protrudes outward to form spines, so it is called echinoderms. 4) Eukaryotic cavity is developed, with special water tube system and peripheral blood system, and the tube foot has many functions such as exercise, respiration, excretion, predation and so on.

arthropoda

Exoskeleton: the body wall of arthropod includes a layer of epithelial cells, which are arranged neatly on the basement membrane. Epithelial cells secrete a layer of hard horny membrane, which covers the whole body, and plays a role in protecting, supporting exercise, feeling stimulation and preventing a large amount of water evaporation in the body. This is an exoskeleton, which is mainly composed of chitin and protein.

Molting: The exoskeleton of arthropods cannot expand after secretion, which limits the growth of worms. When the body grows to a certain extent, it will take off the old skin and form new skin again. When the new skin is not ossified, it will absorb a lot of water and make the body expand rapidly. This phenomenon of molting old skin is called molting.

Trachea: respiratory organ of terrestrial arthropods, which is produced by ectoderm and is invaginated by body wall. Its outer end communicates with the outside world through a valve, and its inner end extends and branches in the body, reaching into the tissue to directly contact with cells, transporting oxygen and discharging carbonic acid gas.

Heterogeneous segments: The arthropod body is divided into many segments from front to back, which are differentiated and have different functions and structures.

Arthropods: Arthropods have solid appendages, developed muscles, movable joints at the joints connected with the body, and also move in segments. This appendage is called an arthropod.

Martensite duct: refers to the excretory organ of arthropods. Most of the tubules from the midgut and hindgut are directly immersed in the blood in the blood cavity, which can absorb a large amount of decomposition products of protein by uric acid, make them pass through the hindgut and be discharged from the anus together with food residues.

Metamorphosis: During the growth and development of insects from egg to mature stage, not only the body gradually becomes larger, but also a series of changes such as morphology, internal structure, physiological function, behavior habits, etc. before they develop into adults. This development process is called metamorphosis, complete metamorphosis and incomplete metamorphosis.

Open-tube circulation refers to the circulatory system of arthropods and some mollusks. The circulatory system consists of a tubular heart with multiple pairs of cardiac holes and a short artery from the front end of the heart. Blood flows from back to front to the head, then from front to back to the blood sinus, and then from the blood sinus to the heart through the heart hole.

Mixed coelom: The coelom of arthropods. In the early stage of embryonic development, there are coelomic sacs, but these coelomic sacs do not expand. The mesoderm of the cyst wall falsely reports that it develops into tissues and organs respectively, and the cavity between the body wall and the digestive tract is formed by the true cavity inside the cyst and the protocavity outside the cyst, so it is called mixed cavity.

Blood cavity: the mixed cavity of arthropods is full of blood, so it is also called blood cavity.

Incomplete metamorphosis: a type of insect metamorphosis, which means that there is not much difference between the morphology of adults and larvae, but the immature wings of reproductive organs are not fully developed, and the life history goes through three stages: larva, nymph (or larva) and adult. Such as locusts and dragonflies.

Book lung: a page-like structure formed by invagination of the body wall of arthropods, whose function is to breathe, such as spiders.

Chemotaxis: refers to the number of generations of insects in a year, from which there are terms such as chemotaxis, chemotaxis and chemotaxis. The corresponding insects are called chemotaxis, chemotaxis and chemotaxis.

Different legal divisions and their significance; The body consists of many different body segments, that is, body segments differentiate, and the same body segments heal to form different body segments, such as head, chest and abdomen. The appearance of irregular segmentation enhances the movement of animals and improves their adaptability to environmental conditions.

The structure and source of exoskeleton: the hard and lifeless chitin structure secreted by epidermal cells on the body surface, which has many functions such as protecting and preventing water evaporation in the body. Its structure includes three layers: upper epidermis, outer epidermis and inner epidermis. It plays an important role in the adaptation of arthropods to land life.

Arthropod trachea and its function: an efficient respiratory organ formed by invagination of the body wall, consisting of valves, trachea and many branch bronchi, with longitudinal and transverse organs in the body. Because the trachea directly transports oxygen to the target tissues and organs, it is very effective and is a way for arthropods to use oxygen in the air.

What are the adaptation characteristics of arthropods to land life: 1? Thick exoskeleton: prevent water evaporation and play a protective role; 2. Body segmentation and appendage segmentation: realize exercise and support; 3. Strong striated muscles: strengthen the function of exercise; 4. Developed nervous system and sensory organs: responding to changing environmental conditions on land; 5. Efficient tracheal breathing: effective use of oxygen in the air; 6. efficient.

The main characteristics of Arthropoda: 1. Exoskeleton with chitin has molting phenomenon during its development. The body is divided into specific segments and obviously irregular segments, which can generally be divided into three parts: chest and abdomen. There are segmented appendages, usually one pair per segment. They have multiple functions. It has a mixed body cavity and an open circulatory system, and the heart is behind the digestive tract. It has an efficient respiratory organ-trachea, which breathes through trachea, gills, book cheeks, book lungs and body surface. The muscles are all striated. Bundle, strong contraction 7. The digestive tract is complete, the mouthparts are composed of head and appendages, and the digestive system is developed 8. The excretory system is the basal ganglia homologous to the body cavity tube, or the Markov tube connected with the digestive tube. 9。 Sensory organs are sensitive, the nervous system is developed, and the ganglion has a healing trend of 10. Androgyny, generally hermaphroditism, mostly fertilization, ovulation or viviparous, direct and indirect development, parthenogenesis.

Based on the characteristics of arthropods, this paper explains why there are many kinds and wide distribution of arthropods in the animal kingdom: arthropods are the most diverse in the animal kingdom, because they produce new structures suitable for terrestrial life and develop long-distance organ systems to enhance their mobility and adapt to the unpredictable external environment on land, as shown in the following figure: 1. The body is divided into many segments connected back and forth to enhance the flexibility of movement, and heteronomy decomposition leads to the differentiation of structure and function between segments, thus improving the adaptability to the environment. 2。 With chitin exoskeleton, it has the functions of protecting the body, preventing the evaporation of water in the body and receiving stimulation, which conforms to the molting phenomenon in the development project. 3。 With segmented appendages, joints can do various activities and adapt to various functions. 4。 Full-time respiratory organs were created to promote gas exchange. There are five mixed body cavities and open-tube circulatory system, and the complexity of the circulatory system is suitable for the developed respiratory system. Muscles are composed of striated muscles, which can contract rapidly, thus producing agile movements. 7。 The digestive system is complete and the digestion and absorption function is enhanced, which can meet the requirement of increasing energy consumption. 8。 The emergence of excretory organs such as antenna gland, jaw gland and basal ganglia of Martensitic duct meets the needs of vigorous metabolism. 9。 The healed ganglion has developed sensory organs, which can improve the conduction stimulation of the nervous system, integrate information and direct movement. Therefore, we can perceive changes in time and react quickly to adapt to life in various environments. 10。 Most of them are fertilized in vivo, with strong reproductive ability, large offspring population, direct development and indirect development in the development process, and some species are affected by unfavorable environmental factors such as dormancy and diapause to survive.