1. Type Chordata
Chordates are divided into lower (Cranial and Tunicate) and higher (Vertebrates).
Typical characteristics of chordates:
1) the presence throughout life or 1 of the period of the dorsal string - notochord, which acts as an internal axial skeleton. During ontogenesis, it is replaced by the spinal column, which becomes a vertebra.
2) The central nervous system has the form of a tube, its internal cavity is a neurocoel, connected by a neuropore to external environment. The neural tube lies above the notochord and is divided into 2 sections - the spinal cord and the brain.
3) the digestive tube - its anterior section - the pharynx - performs 2 functions - digestive and respiratory. The pharynx is penetrated by gill slits; in aquatic animals, gills appear in their place; in terrestrial animals, lungs appear as protrusions of the pharynx wall.
4) the circulatory system is in the form of a tube, the heart is located on the ventral side under the notochord and the digestive tube.
Characteristics common to invertebrates:
Deuterostomy is formed by breaking through the gastrula wall. At the site of the gastropore, a posterior opening is formed.
Secondary cavity of the body - whole
The presence of metamerism - segmental arrangement of organ systems
Bilateral, bilateral symmetry
Subtype Skullless
Origin:
According to A.N. Severtsov, the ancestors of the skullless were free-swimming, bilaterally symmetrical animals. This group gave rise to two branches. One retained a free-swimming lifestyle and led to vertebrates. The other has adapted to a sedentary, bottom-dwelling or burrowing lifestyle. Subsequently, some skullless animals switched to life in the bottom soil, they developed metalural folds and a peribranchial (atrial) cavity (lancelets and epigonichts). The other part remained to live in the water column (amphioxides).
Taxonomy. Class Cephalochordates
Sem. Brachiostomina– lancelets (European, Asian)
Sem. Amphioxide– characteristic signs of larvae, 1.5 cm.
Sem. Epigonichthids– differ in asymmetry, small lancelets up to 5 cm.
The body is elongated, laterally compressed. The body is covered with a fin fold, in the area of the back it is called the dorsal fin, which passes into the caudal fin, then into the subcaudal fin, metapleural folds run along the sides of the body, they merge with the subcaudal folds. The skin of the lancelet consists of 2 layers:
Single-layer epidermis (unicellular glands, mucus - protective)
Thin gelatinous connective tissue - cutis, or corium
Muscular system: Adjacent to the notochord are 50-80 segments - myomeres. The segments are separated by myosepta (septa).
CNS: There is only a chord in the head. Neurocoel is the rudiment of the brain ventricle. In larvae it communicates with the external environment through a neuropore. In adults, in place of the neuropore is the Kölliker fossa, an organ of smell. The dorsal and abdominal nerves depart from the neural tube.
Digestive system. Breath: The pharynx performs 2 functions - it is an organ of digestion and respiration. The walls of the pharynx are penetrated by gill slits. They breathe oxygen dissolved in water. At the bottom of the pharynx there is a groove - endostyle, on which there is glandular and ciliated epithelium: secretes large number mucus. The intestine is in the form of a straight tube, ending with the anus.
Excretory system: Nephridial. In the anterior part above the pharynx there are about 100 pairs of nephridia (a short, strongly curved tube with holes).
Reproduction: Dioecious. There are gonads. Females have ovaries, males have testes. There are no reproductive ducts. Mature germ cells enter the atrial cavity through cell ruptures. External fertilization, egg development in water.
2. Subtype larval chordates (tunicates)
Tunicates are a branch of chordates. All typical characteristics of chordates are developed only in the larval stage. Some species lead a sedentary lifestyle, others move slowly in the water column. All marine animals feed passively, filtering water flows. Hermaphrodites. Asexual reproduction by budding. The circulatory system is of an open lacunar type.
Class Ascidia. 3 Squads:
Neg. Solitary ascidians– gastroascidia or spherical.
Neg. Synascidia, or Colonial– colonies are connected by another base, united by a common tunic, and have independent oral siphons. Fertilization is possible between different colonies.
Neg. Pyrosomat or Ognetelki– an ascidian-like zooid is formed from a fertilized egg. There is an oral and cloacal siphon. there is a sole. The body is covered with a tunic.
Tunic layers:
1) on the outside there is a hard cuticle, under the cuticle there is a fibrous network impregnated with tunicin (a methane-like substance.
2) two-layer mantle, or skin-muscular sac: 1. layer - epithelium, skin, two-layer. 2. transverse muscle fibers.
Digestive system, nutrition: Oral opening → huge pharynx (gill openings - stigmas; endostyle). The pharynx is a respiratory organ. There is a heart - tube-shaped, the edges contract alternately, creating a pendulum-like movement of the blood.
Organs of excretion and reproduction: renal vesicles, accumulation of urea crystals occurs throughout life. Sex cells enter the water through the cloacal siphon. They are caught by the oral siphon of another individual. Fertilization is external. A tailed larva is formed, which differs sharply from the adult organism in structure. The larva ruptures the egg shells → comes out into the environment. Swims for 2-3 hours. attaches to the substrate → regressive metamorphosis.
Salpa class- floating, sea.
Neg. True salps– colonies exist for a short time.
Neg. Kegmen– polymorphic colonies
Externally, the body resembles a cucumber or a barrel, covered with muscle bands. The entire body is occupied by the atrial and pharyngeal cavities, separated by a dorsal process. Consecutive contraction of the muscle bands from the anterior end of the body drives water from the pharynx into the atrial cavity and forcefully pushes it outward → the salp jerkily moves forward. Salps are characterized by alternating sexual and asexual reproduction - metagenesis. An asexual salp develops from a fertilized egg. A bud-bearing stolum forms on the ventral side of the body, it grows, buds form on the sides, and turns into a chain of daughter individuals. One egg matures in the ovary. The sperm enters through the cloacal siphon and fertilizes the egg there. The egg matures in the ovary, ruptures the egg membranes and is released. The mother's body dies. The embryo is growing.
Appendicular class– floating. A small oval body from which the tail extends. 1 pair of gill openings. A chord, neural tube, and muscle cords stretch from the base to the tail. There is no real tunic. The ectodermal cells of the mantle secrete mucus containing a chitin-like substance. The movement of the tail forces the mucus into a kind of house. Opposite the oral siphon, a lattice of thickened threads of mucus is built. With a blow of his tail he breaks the house and leaves it. It floats for a while. In 2 hours he builds a new house.
Development and reproduction: When an individual has reached sexual development, the sperm come out. The eggs mature in the ovary. The sperm enters the ovary and fertilization occurs. An embryo is formed in the eggs, it grows, and leaves the mother’s body. Goes outside. It looks like an adult, differs only in size.
3. Subtype Vertebrates or Cranials
Main features of vertebrate organization
Body Shape: In aquatic vertebrates, the body is divided into head, trunk, and tail. Terrestrials have a variety of body shapes. The cervical spine appears, and head mobility increases. Unpaired fins are reduced, paired fins turn into limbs. In aquatic animals, the limbs turn into fins for the second time.
Skin: the skin has two layers: 1) outer - epidermis (from ectoderm) 2) inner - corium (dermis) (from mesoderm). Function: protection, metabolism, thermoregulation.
Skeleton: Represented by departments: skull, axial, limb girdles, skeleton of free limbs
Axial skeleton: in the evolutionary series, the notochord is replaced by the vertebral column. The spinal column differentiates, cervical, thoracic, lumbar, sacral, and caudal sections appear.
Skull skeleton: The medulla covers the brain. Parachordalia are formed on the sides of the notochord, and lateral cartilages and trabeculae are formed in front. In bony fish, the skull remains cartilaginous, and a shell is formed on top. In teleosts, ossification occurs and primary or cartilaginous bones are formed. There are 2 types of brain skull: platybasal - a wide base of the skull, the brain is located between the eyes (fish, amphibians, some reptiles) and tropibasal - the eye sockets are close together, the brain part is behind the eyes (birds, mammals). There are several types of attachment of the brain apparatus to the skull:
1) protostyly - jaw and hyoid arches are suspended from the skull (primitive gnathostomes)
2) hyostyly - the pendant is attached to the auditory part of the brain skull
3) amphistyly - the upper element of the jaw arch is connected to the skull with the help of special processes (sharks, bone ganoids)
4) autostyly – the upper element of the jaw arch fuses with the skull.
Musculature: Skeletal, smooth, cardiac. Aquatic animals have a segment-by-segment structure (metomeric). With the transition to the terrestrial image, ribbon-shaped muscles (muscles) are formed. In higher vertebrates, the metomeric structure remains only in the location of the muscles of the spinal column.
CNS: It consists of the brain and spinal cord. The neural tube is differentiated into 2 sections: the head and the spinal cord. In the anterior part, 3 brain bladders are formed: anterior, middle, posterior. Further differentiation leads to the formation of 5 sections. The brain is formed from the anterior part of the forebrain. The posterior part of the forebrain becomes the diencephalon. There are 12 pairs of cranial nerves. Aquatic ones have 10.
Sense organs: Vision – paired eyes. Hearing organs: anatomically connected with the organ of balance. In higher animals, the spiral convoluted canal (cochlea) is the organ of hearing. The organs of smell are immersed in the skin. The organs of taste: taste buds are a cluster of sensitive and supporting cells. In fish, on the fins, in others, in the oral cavity.
Digestive system: Starting from ancient jawed mouthparts, the oral apparatus is sucking; in modern cyclostomes there is a suction funnel; in fish, an oral apparatus armed with teeth is being formed. At the bottom of the oral cavity, a tongue with its skeleton (hyoid apparatus) is formed. Taste corpuscles are scattered in the oral mucosa. The pharynx in aquatic animals is penetrated by gill slits; in terrestrial animals the lungs are connected to it. The pharynx is the esophagus and the stomach. Sections of the stomach: cardiac part (the esophagus flows into), bottom or fundic part, pilaris-intestine (differentiated). Sections of the intestine: colon, small intestine, rectum. It ends either in the cloaca or the anus.
Respiratory system: In aquatic animals, gill slits are formed, in jawless animals gill sacs develop, in fish, gill filaments develop between the gill slits, which together make up the gills. The main function is gas exchange. The amphibian develops air breathing organs - lungs.
Circulatory system: Skullless – closed. The heart first appears in cyclostomes as an extension of the abdominal aorta. At first the heart is 2-chambered. Next, 3-chamber (amphibians, reptiles). Starting with amphibians, there are 2 circles of blood circulation: small and large.
Excretory system:
In vertebrate larvae, a pronephros or pronephros is formed. It is represented by a collection of nephridia. The main element of the kidney is the Malpighian corpuscle. In amniotes, pelvic kidneys (metanephros) are formed.
Reproductive system: Most are dioecious. The ovaries have a granular structure, the testes have a smooth structure. Anamnias are characterized by external fertilization, while some have internal fertilization. Eggs develop only in an aquatic environment. Live births occur. In amniotes, embryonic membranes appear and the amount of yolk increases. Development is not in the aquatic environment.
4. Section Agnathans (class Cyclostomes)
The most ancient primitive vertebrates. They reached their peak in the Silurian-Devonian. By the end of the Devonian, most of them died out. their remains have not been found. Groups of modern agnathans appeared in the Carboniferous.
Class Cyclostomes
Includes modern agnathans. 2 Subclasses. The most ancient class. Representatives (lampreys, hagfish) are characterized by a worm-like shape, bare mucous skin, a mouth opening in the depths of the suction funnel, no jaws, a cartilaginous visceral skeleton, an axial notochord, covered with a thick mucous membrane - a fat pad that covers the spinal cord. Respiratory organs – gill sacs (5-16 pairs). They live in seas and fresh water bodies. There are unpaired fins.
P/cl. Lampreys
1Neg. Lampreys– there are 3 groups based on habitat:
1) Sea lampreys or migratory lampreys- live in the seas. They go to rivers to spawn. Representatives: Atlantic, Caspian.
2) river lampreys- inhabit coastal areas of the seas. Spawning in rivers. Representatives: European river, Japanese.
3) Impenetrable river, lake, and brook lampreys– small, live in one place all their lives, do not migrate.
P/cl. Hagfish– on 2 groups
Group Hagfish-gill sacs flow into a common subcutaneous canal, which opens outward with 1 hole.
Group Bdelostomidae– each gill sac opens outward. From 5 to 16 gill sacs.
Unpaired fins. The caudal fin is equal-lobed, there are 2 dorsal fins. In females, an anal fin develops before spawning. Hagfishes have no dorsal fins.
Veils: The epidermis is multilayered, containing numerous skin cells and secreting abundant mucus (protection).
Skeleton and muscular system: Myochordal complex There is a notochord. The skull is not formed, is at an evolutionary stage, and surrounds the brain only from below and from the sides. Visceral skeleton: consists of 3 sections:
a) Skeleton of the pre-oral infundibulum – elasticity
b) Skeleton of the gill grille – closes the gill sacs
c) Pericardial cartilage – covers the heart.
The muscular system consists of muscle segments - myomeres, separated from each other by partitions - myosepta.
Digestive organs and nutrition:
Respiration and gas exchange: Respiratory organs - gill sacs. Gas exchange occurs in the capillaries of the walls of the gill sacs.
Respiratory tract: in lampreys: Mouth opening → pharynx → respiratory tube → internal openings of gill sacs → 7 pairs of gill sacs → external openings of gill sacs on the side walls of the body. For hagfish: Mouth opening → pharynx → independent openings of gill sacs (5-16 pairs) → gill sacs → gill canal opening outward.
Circulatory system: Closed, 1 circle of blood circulation. There is a 2-chambered heart, 1 atrium and 1 ventricle. Hematopoiesis occurs in the walls of the esophagus and intestines, in the kidneys, and liver.
Excretory system: Excretory organs are paired mesonephric (trunk) kidneys located on the dorsal side of the body above the gonads
Reproductive system and reproduction: Dioecious. The gonads are paired (ovary or testis), occupy almost the entire abdominal cavity of the body. There are no reproductive ducts. Fertilization is external. Lampreys have small eggs. die after spawning and fertilization. They reproduce once in a lifetime. The larva is a sandworm. After 4-5 years, metamorphosis occurs, the sand miner turns into an adult lamprey. Hagfish have large eggs, development without metamorphosis; the egg hatches into a young individual, differing from the adult only in size. Polycyclic.
Nervous system: The brain is small and lies in one plane. The 5 parts of the brain lie without overlapping each other. The medulla oblongata passes into the spinal cord.
Sense organs: Chemical sense organ: nasopituitary sac: Unpaired nostril → nasal passage → olfactory capsule - pituitary outgrowth. Lateral line organ - perception of water currents, registration of approaching objects. There are weak electrical organs, temperature, tactile receptors and chemoreceptors.
5. Section Gastrostomes. Superclass Pisces. Class Cartilaginous fish
Their earliest fossil remains in the form of scales were found in Upper Silurian deposits. Representatives of very diverse species are already found in Devonian deposits. different groups. One of the earliest groups known from the Early Silurian are Armored fish, their body was covered with a bone shell. They lived until the Carboniferous period and then went extinct. Another group were small freshwater acanthodia, whose body was covered with bone plates. Actually cartilaginous fish known from the Late Silurian – Early Devonian. Elasmobranchs experienced two bursts of adaptive radiation - in the Silurian - Devonian and in the early Mesozoic. Since the end of the Mesozoic, modern families of this subclass have taken shape.
External structure: Marine. Torpedo-shaped body. Paired fins appear: pectoral and ventral. The skin is bare or covered with placoid scales. The function of the axial skeleton is performed by the spinal column. Skull hyostelic. 5-7 pairs of gill slits open on the sides of the body. In whole-headed fish they are covered by a common gill cover. The conus arteriosus develops in the heart, and the spiral valve develops in the intestine.
Covers: Fish skin consists of 2 layers:
1) upper - epidermis - multi-layered, it contains a large number of glands that secrete mucus (protective function)
2) corium - the actual skin or dermis - scales are located. The scales consist of plates and a spine lying on it. The main substance is dentin, covered with enamel, the cavity is pulp, vessels and nerves are such scales - placoid.
Skeleton and muscular system: The skeleton is cartilaginous. The skeleton consists of sections: skull, axial skeleton, skeleton of free fins, fin belt. The axial skeleton is represented by the vertebral column: 2 sections - trunk and caudal. The vertebrae are amphicoelous (biconcave). The skull consists of 2 sections - the brain and the visceral. The brain section consists of the olfactory and auditory capsules, rostrum (snout), and orbit. Visceral - consists of 3 arches: gill, hyoid, maxillary. Muscles consist of myosepta,. Feature– muscle autonomy – muscles can contract with disruption of the central nervous system.
Digestion and nutrition: Predators and filtrates. rectal gland (reservoir for salt accumulation). Large, three-lobed liver (up to 25% of body weight), source of vitamin A.
Respiratory organs: They breathe oxygen. Respiratory organs - gills.
Inhalation-exhalation mechanism: When inhaling, the gill arches diverge to the sides. Water enters the mouth, then into the pharynx, and passes into the outer gill slits. When you exhale, the gill arches move closer together, and water is pushed out.
Circulatory system: The heart consists of the venous sinus, atrium, ventricle, abdominal aorta, it begins with the conus arteriosus. The spleen first appears, which lies near the stomach and serves as a blood depot and is a hematopoietic organ.
The excretory organs are the kidneys (trunk), in the form of ribbon-like bodies, they lie immediately under the spinal column.
Reproductive system: Dioecious, internal fertilization. Males: testisàvas deferensàrenal tubulesàWolffian canalàcloacaàgenital tract of the female. Female: ovaryàthere is no connection between the ovary and the oviduct (ovumàbody cavity)àin 1/3 of the oviduct fertilization. The eggs are large, covered with a horn-like shell.
CNS: The brain has 5 sections: anterior, posterior, medulla oblongata, middle, intermediate. The medulla oblongata passes into the spinal cord. There are 10 cranial nerves that arise from the brain.
Sense organs: The main receptor is the sense of smell - The olfactory sacs communicate with the external environment through the nostrils. Capable of echolocation - capturing waves reflected from the bottom and objects. Seismosensory organs - lateral line, openings. Lorenzinium ampoules - allows you to find prey. Eyes with large crystals, fixed eyelid. Hearing organs: inner ear only.
Taxonomy
The class is divided into 2 subclasses: P/Cl. Elasmobranchs And P/Cl. Whole-headed.
1) P/Cl. Elasmobranchs
· N/neg. Sharks
Neg. Placiformes
Neg. Polybranchids
Neg. Heterodonates
Neg. Lamniformes:Sem. Fox sharks, Sem. Herrings, Brownie shark
Neg. Carharhiniformes or sawtooths:Sem. Gigantic, Sem. Gray, Family Felines
Neg. Katraniformes (spiny) sharks
Neg. Sawtooth
Neg. Squatiniformes or sea angels
N/neg. Stingrays
Neg. Sawfishes (sawfish)
Neg. Rochleiformes
Neg. Diamond-shaped or diamond-bodied rays
Neg. Eaglets or stingrays:Sem. Orlyaki, Sem. Horned rays
Neg. Gnus-shaped or electric rays
2) P/Cl. Whole-headed– the body is valval, skin ossifications are developed – gill covers. The skull is autostyle. The teeth merge into dental plates. The interbranchial septa are reduced. Neg. Chimeraformes– the first dorsal fin has a spine. The tail is in the form of a tourniquet. Marine. The female lays 1-2 eggs with a thread-like appendage.
6. Class Bony fish
Bone scales develop in the skin. The skull is hyostylic or amphistylous (loosely connected to the skull). The tail is hetero-, homo-diphycercal. 5 pairs of gill slits, covered by a common operculum. The swim bladder is formed. Some have lungs (double breathing), some retain the conus arteriosus (carpal fins), and the rest are replaced by an aortic bulb. Fertilization is external, some are internal - there is a capulative organ - the outgrowth of the anal fin. Neutral buoyancy – 2 types: open- and closed-buoyancy. Functions of the swim bladder: hydrostatic, participation in gas exchange, is a baroreceptor, creation and amplification of sounds.
Covers: Consists of 2 layers:
1) multi-layered epidermis - a large number of glands that secrete mucus
2) corium - cells are colored, called chromatophores - provide a change in color under the influence of the central nervous system. Scales are protective bone formations in the skin. Lobe-finned fish have cosmoid scales in the form of a bony plate, externally covered with cosmin. From the cosmoid scale arose ganoid scales covered with ganoid. Ganoid scales can fuse with each other, forming a shell. The usual scales are cycloid; in the area of the lateral line, the scales have holes that communicate with the lateral line canal.
Digestive system: There is a language. The glands secrete saliva without food enzymes. There is a liver, spleen, gall bladder.
Respiratory organs: 2 types of breathing: air and water. Aquatic: oxygen from water – gills. Air - from the air - swim bladder, lungs, sections of the intestinal mucosa.
Excretory organs, water-salt metabolism: kidneys, gill apparatus, skin, digestive tube, liver. filtering apparatus of the kidneys, many vascular glomeruli - glomerulus
Reproductive system: Dioecious. Males have testes, females have ovaries. In lobe-fins, the reproductive and excretory systems are connected, the vas deferens flows into the kidney. Wolffian canal is a function of the vas deferens and ureter, Müllerian canal is a function of the oviduct. caring for offspring.
CNS and sensory organs: The brain is divided into 5 sections: anterior (olfactory lobes). Diencephalon. Midbrain (2 optic lobes). The cerebellum covers the medulla oblongata. Eyes.
SYSTEMATICS:
1. P/cl. Lobe-finned– cosmoid or bony scales. The notochord is maintained throughout life. The paired fins are covered with scales. The fin is of the bysseral type. In the intestine there is a spiral valve, in the heart there is a conus arteriosus. There is a cesspool.
1) N/neg. lobe-finnedNeg. Coelacanths
2) N/neg. Dipnoi Neg. Horntoothed or monopulmonate,Neg. Dipulmonary
2. P/cl. Ray-finned– ganoid or bony scales. There are naked ones, with shells. Joan no. The fins are formed by bony rays - lipidotrichia → name. The conus arteriosus is replaced by the aortic bulb. Instead of lungs, a swim bladder.
Cartilaginous ganoids
Neg. Sturgeon Sem. Sturgeon fam. Paddlefish
Neg. Multi-feathered
Bone ganoids
Neg. Amiiformes
Neg. Carapaceans
3. P/cl. Bony- bone scales. Large degree ossification. Bone rays are developed that support the leathery edge of the gill cover. In the heart, instead of the arterial cone, an aortic bulb appears. The swim bladder is devoid of cellularity. The intestine does not have a spiral valve. 1 dorsal fin, the second, if present, is fatty without bony rays.
1 ) N/neg. Clupeoid (herring)
Neg. Herring Sem. Herring Fem. Anchovy
Neg. Salmonidae
Neg. Cetaceans
Neg. Myctophiformes
2) N/neg. Aravanoides
Neg. Aravanidae
Neg. Beaked whales
3 ) N/neg. Angveloides
Neg. Eels
Neg. Sacrumata
Neg. Spinociformes
4) N/neg. Cyprinoids
Neg. Carp-like
Neg. Catfish
7) N/neg. Percoid
Neg. Sticklebacks
Neg. Mullet-shaped
Neg. Perciformes
Neg. Flounders
IN THE ORIGINAL REGION: Carp family (rudd, asp, tench, podust, gudgeon, bleak, round crucian carp, carp). from the loach family, from the catfish family, catfish from the perch family, pike perch, bersh, perch, from the cod family, burbot.
7. Superclass Quadrupeds. Class Amphibians or Amphibians
4 classes – Amphibians, reptiles, birds, mammals.
Amphibians - anamnia (primary aquatic): 1) main development in the aquatic environment 3) there is a metamorphosis stage 4) eggs develop without the formation of embryonic membranes
Origin and evolution. The transition of vertebrates from an aquatic to a terrestrial lifestyle is accompanied by the appearance of breathing atmospheric oxygen and movement on a solid substrate. At the same time, other organ systems also changed: the integument, blood circulation, sensory organs, and nervous system. The first amphibians that appeared in fresh water bodies at the end of the Devonian were Ichthyostegids. They were real transitional forms between lobe-finned fish and amphibians; they had rudiments of a gill cover and a real fish tail. The skin was covered with small fish scales. However, along with this, they had the paired five-fingered limbs of terrestrial vertebrates. Subsequently, in the Carboniferous period, a number of branches arose ( labyrinthodonts). In the Carboniferous, the second branch of primary amphibians arose - lepospondyls - stegocephals(shell-headed) for a solid shell of skin bones covering the skull. The ancestors of stegocephalians were bony fish. Closest to stegocephalians lobe-finned fish. Stegocephalians lived until the beginning of the Mesozoic. Modern orders of amphibians were formed only at the end of the Mesozoic. intensive speciation of modern amphibians began in the early Mesozoic.
Amphibian class. Adults are characterized by paired limbs with a hinged joint, unequal. The skull is attached to 1 cervical vertebra, forming the atlas - occipital joint (the head is mobile). The upper element of the hyoid arch - the dewlap - turns into the auditory bone of the middle ear - the stapes. The pelvic girdle connects to the transverse processes of the sacral vertebra. Two circles of blood circulation are formed, but they are not completely separated. The lateral line organs disappear in adults. Signs of aquatic animals: 1) skin is permeable to water 2) trunk (mesonephric) kidneys 3) body temperature depends on the ambient temperature - poikilothermia . Eggs are laid only in water. Larva → metamorphosis → adult.
Leather: Consists of 2 layers: epidermis (multilayered) and corium (thin, with capillaries). The skin is rich in glands that secrete mucus. In those living in dry places, this mucus thickens, forms a film, and reduces moisture loss. The secretion can be poisonous (bellied toad, toad). The corium contains pigment cells. Epidermal cells become keratinized, claws and nails appear. In legless animals, bone scales are scattered in the corium. Tailless animals have lymphatic lacunae under their skin - reservoirs that, under favorable conditions, allow them to accumulate water reserves.
Muscular and digestive system: The muscles of the limbs increase, and the complexity of the oral cavity becomes more complex. All adults are carnivores; larvae can feed on algae and detritus. Prey is captured using the tongue. There is a pancreas and a liver.
Respiratory organs: Respiratory function - skin, lungs, mucous membranes of the oropharyngeal cavity. In larvae, this function is performed by the skin, external and internal gills. Breathing mechanism: Ventilation of the lungs occurs due to the movement of the bottom of the oropharyngeal cavity.
Circulatory system: The heart has 3 chambers. The blood mixes in the ventricle. Vena cava appears, it is paired, formed by mixing 3 veins, the blood is mixed. Bone marrow appears for the first time.
Excretory organs, water-salt metabolism: The larvae have head buds (forebuds). During metamorphosis, trunk buds appear. There is a bladder. Decomposition products: in larvae - ammonia, in adults - urea.
Reproductive system: paired gonads. The function of the oviduct is the Müllerian canal.
In males: testes → seminiferous tubules → kidney, there they open into the Wolffian canal, the lower part of which forms a swelling - the seminal vesicle (a reservoir for storing reproductive products). In anurans, fertilization is external (males have genital calluses on their paws to hold the female). In caudates it is internal. Neoteny – the ability of larvae to reproduce sexually (ambistoma, axolotl) (under unfavorable conditions)
CNS, sensory organs: Larvae have lateral line organs. The sense of smell is well developed, there are external nostrils. Jacobson's organs are necessary for the perception of the smell of food in the mouth. Almost everyone has developed visual organs. Color perception is developed.
Taxonomy
P/Class Arcuvertebrates
N/neg. Jumping
Neg. Primitive anurans
Neg. Anurans– flattened body, small limbs, large head. The hind limbs are powerful, pushing.
Sem. Round-tongued– Patronizing coloring. Midwife toad - the female lays eggs in the form of cords, the male fertilizes them and carries them on his paws until hatching.
Sem. Pipovye– Surinamese pipa – the female lays eggs on her back, the male fertilizes them and presses them into the skin. Cells form around the eggs. They stay there until they become frogs.
Sem. Garlics
Sem. Toads– Representatives: yeah, leaf frogs. in Russia – gray and green toads. Behind the eyes there are poisonous glands - parotids.
Sem. Tree frogs– the tips of the paws are expanded into discs (suction cups). Caring for offspring. Representatives: blacksmith tree frog (they build a pool where they lay eggs), marsupial tree frog - a bag on the back where eggs are laid
Sem. Real frogs– Goliath frog, brown, grass, green frogs
Sem. Copepods
P/Class Thin vertebrae
Neg. Tailed– body compressed from the sides, small head, tail-balancer, limbs on the sides, small, equal
Sem. Siren– originated from neotenic larvae of ambystoma. There is no adult stage. There are only forelimbs, external gills are preserved throughout life, there are lungs
Sem. Proteaceae– neotenic salamander larvae. There are external gills. Fertilization is internal. Representatives: European, American. Proteus
Sem. Real salamanders– gills are reduced, there are ovoviviparous and viviparous
Sem. Tritons- winter on land. Representatives: common newt and crested newt
Sem. Lungless salamanders
Neg. Legless– Representative: caecilians – worm-like body, small head. Constrictions divide the body into segments. The limbs and their belts are missing, there is no tail, and there is a cloaca at the end of the body. They secrete poisonous mucus. Underground lifestyle, some aquatic. Viviparous.
8. Class Reptiles or Reptiles
Signs of amniotes:
1) Embryonic development in the air with the formation of embryonic membranes (serous, amnion, allantois)
2) The eggs are large, covered with a shell shell
3) Internal fertilization
4) Increased care for offspring
5) Lack of larval stage
Origin of reptiles: Land vertebrates arose in the Devonian. These were armored amphibians, or stegocephali. They were closely associated with bodies of water, since they reproduced only in water and lived near bodies of water, where there was terrestrial vegetation. Reorganizations: adaptations to protect the body from desiccation, to breathe atmospheric oxygen, and to walk on a solid substrate. All of the above traits took shape in reptiles. Mesozoic reptiles are primarily terrestrial animals. Many of them have adapted to life in water. Some have mastered the air. The oldest reptiles are known from the Upper Permian deposits of North America, Western Europe, Russia and China. They are called cotylosaurs. Most groups acquired greater mobility; their skeleton became lighter, but at the same time stronger. The solid shell of the skull has undergone partial reduction. Today's cryptonecked and side-necked turtles largely retain the primary appearance of Triassic land turtles. Marine and soft-skinned animals appeared in the late Mesozoic. Crocodiles appear at the end of the Triassic. Jurassic crocodiles differ from modern crocodiles in the absence of a true bony palate. The vertebrae were still amphicoelous. Modern crocodiles descended from ancient archosaurs - pseudosuchians. They are known from the chalk. By the end of the Mesozoic everything greater development received highly organized birds and mammals.
Veils. The skin is dry, devoid of glands, breathing is due to the movement of a closed chest (snakes do not have it). The skin is a multi-layered epidermis. The upper layer is the stratum corneum, the lower layer is the Malpighian layer (living, germinal). Skin ossifications (plates) lie in the skin. The skin has lost its ability to penetrate water and gases. Under the epidermis is the corium, in the upper layer of which there are pigment cells (color).
Skeleton. In the axial skeleton: cervical, thoracic, lumbar, sacral, caudal. In the cervical, the first 2 vertebrae are differentiated (atlas and epistrophy). The lumbar region has short ribs. Capable of autotomy (dropping the tail).
Circulatory system. An incomplete septum appears in the heart. Mixed blood with a predominance of arterial blood.
Digestive system: Mostly predators. The oral cavity contains glands without enzymes. In poisonous ones, they become poisonous. There is a liver and pancreas.
Excretory organs: The kidneys are metanephric and are located in the pelvic cavity. 2 types of filtration:
1. those that live in water have a well-developed filtering apparatus (glameruli and nephron). Products are released into the lumen by filtering blood plasma. 2. in land animals – the secretory apparatus of the renal tubules is strengthened. The end product of metabolism is uric acid.
Reproductive system: Dioecious.
CNS and sensory organs: The brain enlarges. The olfactory lobes are developed, there is a pituitary gland and an epiphysis. The cerebellum enlarges. There are 11 pairs of cranial nerves. The hearing organs are the middle ear (it contains the stapes) and the inner ear.
Taxonomy
1) P/cl.Anapsida (neg. Turtles)
2) P/cl. Archosaurs (detail Crocodiles)
3) P/cl. Lepidosaurs (beaked order, Squamate order)
1) P/cl.Anapsida
Neg. Turtles– Modern ones have a shell consisting of a dorsal shield - the carapace and an abdominal shield - the plastron. The carapace is formed by bone plates of skin origin. The ribs and the trunk part of the spine are fused with it. The plastron is formed from bone plates. The top of the carapace is covered with horny scutes. Only the caudal and cervical sections are movable; the rest is fused with the carapace. Jaws without teeth. The lungs are well developed. Additional respiratory organs are paired anal bladders and pharyngeal outgrowths. Well developed vision and sense of smell. 5 suborders: P/neg. Hidden-necked turtles Sem. Freshwater,Sem. Land;P/neg. sea turtles; P/neg. Soft-skinned turtles; P/neg. Side-necked turtles; P/neg. Shieldless turtles
2) P/cl. Lepidosaurs
Neg. Beakheads– 1 type. Tuatara or Hatteria - oldest species among modern ones. Up to 70 cm. Island of New Zealand. Guarded.
Neg. Scaly
P/neg. Chameleons– a keel runs along the back. The limbs are transformed into grasping pincers in the form of 2 opposed groups of fingers. Eyelids fused.
P/neg. Lizards – Sem. Geckos; Sem. Iguanas– marine, arboreal, terrestrial; Sem. Agamas; Sem. Real lizards–viviparous.; Sem. Spindlefish; Sem. Monitor lizards– the largest, arboreal, terrestrial; Sem. Venomous teeth– 2 types. Poisonous; Earless monitor lizards.
P/neg. Amphisbaenas (two-walkers)
P/neg. Snakes- Legless. They are able to open their mouth wide – a movable joint of the bones of the facial part of the skull. Poisonous ones have poisonous glands and teeth. Belts and limbs are missing. Sem. Slepuny– burrowing lifestyle; Sem. Pseudophods; Sem. Colubridae;Sem. Aspidae- mostly poisonous. Sem. Sea snakes. Sem. Viperaceae Sem. Pitheads.
P/cl. Archosaurs
Neg. Crocodiles
The body is ovate, covered with horny scutes. The nostrils open on the tubercles, the eyes are raised above the surface of the muzzle. On the head and at the anus - odorous glands (mark the territory) lay up to 100 eggs, bury them in the sand. They live up to 180 years. Sem. Alligators, Sem. Real crocodiles, Sem. Gharials– 1 species – Gavialus Hanveticus (Hindustan)
9. Bird Class
Origin of birds. P Rare were the ancient saurian reptiles - archosaurs. By the beginning of the Mesozoic (Triassic) - birds. The birds are closest to the squad thecodonts. The evolution of the group proceeded by adapting to climbing trees, in connection with which the hind limbs served to support the body on a solid substrate, and the forelimbs were specialized for climbing by grasping branches with the fingers. Subsequently, the ability to jump from branch to branch developed. The scales of the forelimb formed the feather rudiments of the wing plane. An important stage in the development of birds is the transformation of scales into feathers, which first developed on the wings and tail, and subsequently spread throughout the body. The appearance of feathers not only made it possible to fly, but also played a very important thermal insulating role and determined the homeothermic nature of birds. The immediate ancestors of birds have not yet been established. In the last century, in Jurassic deposits, they were found and described Archeopteryx. Currently, seven paleontological remains of Archeopteryx are known. Archeopteryx is characterized by many features of reptiles: the absence of a horny beak, the presence of teeth, a narrow and keelless sternum, and abdominal ribs.
Covers: The skin is thin, dry, devoid of glands. The layer of skin is divided into the skin itself - the dermis, blood vessels pass through it, the feather edges are strengthened, and muscle fibers are located. The second layer is subcutaneous tissue - a loose layer adjacent to the muscles that accumulates fat reserves. One gland - the coccygeal gland (well developed in waterfowl) - produces a fat-like secretion. Lubricate the feather, prevents it from getting wet, a source of vitamin D. The growth of the stratum corneum of the skin forms the horny covering of the beak - rhamphotheca. Horny scales cover the fingers, grip, and part of the lower leg. In some species, males develop a bony outgrowth on the chain - a spur.
Pen types, structure: The main feather is contour, consists of a shaft, with 2 fans on the sides. The part of the trunk to which the fan is attached is called the stem. The lower part is a frame, secured in a feather bag. Each fan is formed by horny plates - barbs of the 1st order, from which thin barbs of the 2nd order extend, with small hooks located on them. The hooks are fastened to each other and form a blade of the fan. Pigments accumulate in feathers - melanins (black, brown color) and lipochromes (red, yellow, green). Contour feathers are strengthened in the skin in special fields - pterilia; they alternate with fields where there are no feather edges - apterilia. Under the contour feathers there are down feathers (thin shaft, beards without hooks).
Propulsion system: The peculiarity of the structure of the neck muscles allows them to turn their heads by 180 0, in owls by 270 0. The thoracic vertebrae fuse into the dorsal bone, connect to the sacrum, and the trunk section is motionless. There is a large sternum with a process - a keel - for attaching muscles involved in flight. The tail vertebra turns into the coccygeal bone - pigastyle, and the bases of the tail feathers are attached to it. The jaw turns into a beak. The collarbones grow together into a fork - the role of a shock absorber during the flapping of the wing.
Digestion: Filter-feeders have a fleshy tongue, nectar-feeders have a tongue that curls into a tube, and woodpeckers have hooks. Salivary glands (some have amylase). Some have a goiter - an enlargement of the lower part of the esophagus (temporary storage of food when the stomach is full; in pigeons, goiter cells undergo fatty degeneration - bird's milk).
Breath: Through the nostrils, air enters the nasal cavity → choanae → oral cavity. There are 2 larynxes - the upper (does not have vocal cords), behind which is the trachea, and the lower (forms the vocal apparatus). The source of sound is vibration as air passes through the membranes.
Inhalation and exhalation is carried out due to the movement of the chest. Oxygen saturation occurs continuously during inhalation and exhalation (double breathing).
Excretion, water-salt exchange: kidneys → ureters → cloaca. The metabolic product is uric acid. A loop-shaped section appears in the nephron - the loop of Henle (water readsorption) - which allows the removal of harmful substances.
Reproductive system: In females: only 1 left ovary develops. Fertilization occurs in the upper part of the oviduct. Holases (cords) - a dense part in the egg - allow the yolk to spin, the germinal disc will always be on top. The smaller the bird, the larger the clutch. Sexual dimorphism is pronounced.
Nervous system, sensory organs: 12 pairs of cranial nerves. The main receptor is vision. Color vision. Recognize sweet, bitter, salty. Thermoreceptors, touch receptors.
Taxonomy:
Aquatic and semi-aquatic birds
N/neg. Floating
Neg. Penguin-like Neg. Loons Neg. Grebes.Neg. Shearwaters (Tubenoses) Neg. Pelicans (Copepods) Neg. Cioriformes Sem. Herons, Storks, Ibises, Flamingos . Neg. Anseriformes
Birds of open landscapes
Neg. Ostriches Neg. Rhea-shaped Neg. Cassowaries Neg. Kiwiformes (Wingless) Neg. Falconiformes P/neg. Amer. Vultures P/neg. FalconsSem. Accipitridae, Falconidae. Neg. Galliformes Neg. Crane-like Sem. True Cranes, Bustards Neg. Pigeonidae Neg. Parrots Neg. Cuckoo-like Neg. Owls Neg. Swift-shaped P/neg. Swifts P/neg. Hummingbird Neg. Woodpeckers P/neg. Primitive woodpeckers P/neg. Real woodpeckers Neg. Passeriformes P/neg. Broadbills P/neg. Screaming P/neg. Passeriformes Sem. Larks Sem. Swallows Sem. Ravens Sem. Tit fam. Blackbirds Sem. Wagtails Sem. Starlings Sem. Finches
10. Class Mammals or Animals
The progressive evolution of mammals was associated with the acquisition of: high body temperature, the ability to thermoregulate, and a high aerobic metabolic rate. This was facilitated by changes in the respiratory and circulatory systems: this was expressed in the division of the heart into four chambers and in the preservation of one aortic arch, which determined the immiscibility of arterial and venous blood, in the appearance of a secondary bony palate, which ensured breathing during meals and accelerated digestion of food. changes in the structure of the jaws, differentiation of teeth, development of jaw muscles. The animal-toothed reptiles closest to mammals were cynodonts. The most striking features of skeletal changes were found among them in Trinaxodon from the Early Triassic. In the subsequent development of mammals, paleontologists emphasize changes in the dental system. This led to the identification of two groups - morganucodontod And cuneotheriids→eupanthotherians. Biologically, they were to a certain extent close to terrestrial and arboreal insectivores. At the end of the Mesozoic, the division into two independent trunks - Inferior, Marsupials, And Higher, Placental. The most ancient group of marsupials is the opossum family.
Placental Mammals arose during the Cretaceous period. Fossil monkeys have been known since the Paleocene. Tree monkeys - propliopithecus- gave rise to gibbons and similar anthropoids, Ramapithecus. Of great interest Australopithecuses. The class of mammals is of pyphyletic origin, i.e. its individual branches arose from different groups of animal-like reptiles. Modern Mammals are divided into:
1) Pioneers (first animals)
2) Real mammals (animals)
There are oviparous mammals.
Covers: 1) Epidermis (multilayered, keratinized) → dermis → fiber. The epidermis is the lower layer of cells; they become keratinized and rejected (dandruff). Derivatives of the epidermis - hair, nails, etc. the epidermis contains a pigment - melanin (coloring, tanning, protection from sunlight). 2) Corium (skin itself) - formed by fibrous tissue, rich in blood vessels. The lower layer of corium is subcutaneous fatty tissue.
2 types of hair: guard (long, hard) and downy (soft). The guard hair consists of a shaft protruding outward and the base of the bulb, fixed in the dermis. Glands (derivatives of the epidermis): sebaceous glands - their ducts open into the hair follicle. The secret lubricates the skin and hair; sweat - open anywhere on the surface of the skin (thermoregulation). A modification of the sweat glands is the mammary gland. There are sensitive hairs - virbis (touch), the root of which is located in the blood lacuna.
Skeleton, muscular system: The number of bones increases. Axial skeleton - cervical, thoracic, lumbar, sacral, caudal. All have 7 cervical vertebrae. The thoracic region is a closed chest. There are false edges (not connected). The skull has a zygomatic arch. Limb girdle – scapula, collarbone. Free section – shoulder, forearm, hand. Girdle of pelvic limbs - pelvis (closed - fused with the help of bone fusion - symphysis), thigh, lower leg, foot.
Digestive system Oral apparatus – lips, teeth, tongue, cheeks, gums. Heterodontism (different teeth) – incisors, canines, small and large molars. Salivary glands - enzymes (amylase), bactericidal substance (lysozyme), stomach - single-chamber (carnivores) and multi-chamber (herbivores), consists of sections - rumen, mesh, book, abomasum.
Respiratory system: Breathing through the movement of the chest. Oral or nasal cavity → larynx → trachea → lungs (ending in alveoli). 2 types of breathing - abdominal (predominant in herbivores) and thoracic (predominant in carnivores).
Circulatory system: The heart has 4 chambers, 2 atria, 2 ventricles.
Excretory organs: The kidneys are pelvic, metanephric (in the pelvic cavity). They consist of 2 layers - the cortex and the medulla. The unit of the kidney is the nephron. Metabolic products are urea.
Reproductive system: In males: the testes are placed in the scrotum. Around the testes is the epididymis (maturation of germ cells), from which the vas deferens opens on the seminal mound at the root of the penis. In females: paired ovaries → oviducts, open next to the uterus. Types of uterus: double (2 bodies, 2 horns, 2 vaginas; in rodents), bicornuate (dogs, pigs), simple (in primates, humans), bipartite. The cervix opens into the vagina. The ovaries mature in the follicle - Graf's vesicle. The egg enters the ventral genital funnel. Fertilization occurs in the upper part of the oviduct.
Taxonomy
P/class Cloacae (first beasts) - The most primitive ones. They lay eggs and hatch them. Neg. MonotremesSem. Yakhidny– the body is covered with needles and has a beak. Sem. Platypuses- semi-aquatic, membranes between the fingers. Strain the water.
P/class Animals
N/neg. Marsupials
Neg. Marsupials– Cubs are born premature and carry to term in a pouch. The bursa contains mammary glands. Sem. opossums, Sem. Carnivorous marsupials, Sem. Marsupial badgers (bandicoots), Fam. Couscous- herbivores, Sem. Kangaroo
N/neg. Higher animals (Placental)- capable of sucking milk
Neg. Insectivores Sem. Hedgehogs- in Orenb. Region – eared and common hedgehog, omnivores, Sem. Moles, Sem. Shrews– the smallest – tiny little shrew (2-3 g)
Neg. Woolwings (kaguans) Neg. Chiroptera– echolocation, active at night
P/neg. Fruit bats
P/neg. Bats They feed on blood, nectar, insects Sem. Bagwings, Sem. Piscivores, Sem. False vampires, Sem. Vampires, Sem. Common bats
Neg. Partial teeth– characterized by underdevelopment of teeth. Sem. Anteaters,Sem. Armadillos
Neg. Lagomorpha Sem. pikas, Sem. Hares
Neg. Rodents Sem. Beavers, Sem. Squirrel, Sem. Jerboas, Sem. Mouse, Sem. Hamsteriformes, Sem. Agouti, Sem. Chinchilla
Neg. Cetaceans– forelimbs are flippers, hind limbs are absent.
P/neg. Baleen whales Sem. Right (true) whales, Fem. Gray whales, Sam. Stripes
P/neg. Toothed whales– there are teeth (uniform). Sem. River dolphins, Sem. Sperm whales, Sam. Dolphins
Neg. PredatorySem. Canine, Sam. Raccoons, Sam. Bears, Sam. Cats, Sam. Hyenas
Neg. Pinnipeds Sem. Eared seals, Sem. Real seals, Sem. Walruses
Neg. Odd-toed ungulates– the phalanges of the fingers end in the hoof. Sem. Tapirs, Sem. Rhinoceroses
Neg. Artiodactyls – even number fingers
P/neg. Non-ruminants– stomach simple, limbs 4-fingered Sem. Pigs,Sem. Bakers,Sem. Hippos
P/neg. Ruminants-The stomach is complex. Belching food - chewing gum. Sem. Musk deer, Sem. Deer, Sem. Giraffes
P/neg. Calloused– limbs have 2 fingers, no hooves Sem. Camels
Neg. Primates– 5-toed, plantigrade. 1 finger is opposed to the rest. Heterothed. Big brain, convolutions appear
P/neg. Lower primates (prosimians)Sem. Tupaii– primitive, woody Sem. Lemurs, Sem. Laurie– woody, tropics
P/neg. Great apes (monkeys) Broad-nosed monkey section: small marmosets, callimico and large capuchin monkeys. Narrownose section: Sem. Monkeys,Sem. Gibbons, Sem. Hominids
Type Chordata
Lower chordates. Subtype Skullless
TYPE CHORDATES. LOWER CHORDATES
General characteristics of the type Chordata
The phylum Chordata unites animals that are diverse in appearance and lifestyle. Chordates are distributed throughout the world and have mastered a variety of habitats. However, all representatives of the type have the following common features of the organization:
1. Chordata are bilaterally symmetrical, deuterostome, multicellular animals.
2. Chordates have a notochord throughout their entire life or at one of the phases of development. Chord- This is an elastic rod located on the dorsal side of the body and performs a supporting function.
3. Located above the chord nervous system in the form of a hollow tube. In higher chordates, the neural tube is differentiated into the spinal cord and brain.
4. Located under the chord digestive tube. The digestive tube begins mouth and ends anus, or the digestive system opens into the cloaca. Throat pierced gill slits, which in proto-aquatic animals persist throughout their lives, but in terrestrial animals are formed only in the early stages of embryonic development.
5. Beneath the digestive system lies heart. Circulatory system in chordates closed.
6. Chordates have secondary body cavity.
7. These are chordates segmented animals. Location of organs metameric, i.e. major organ systems are located in each segment. In higher chordates, metamerism is manifested in the structure of the spinal column and in the muscles of the abdominal wall of the body.
8. The excretory organs of chordates are diverse.
9. Chordates are dioecious. Fertilization and development are varied.
10. Chordata evolved through a series of intermediate forms unknown to biology from the very first coelomic animals.
The phylum Chordata is divided into three subtypes:
1. Subtype Skullless. These are 30-35 species of small marine chordates, shaped like fish, but without limbs. The notochord in the Skullless Ones is maintained throughout life. The nervous system is in the form of a hollow tube. The pharynx has gill slits for breathing. Representatives – Lancelets.
2. Subphylum Larvalchordates, or Tunicates. These are 1,500 species of sedentary, sedentary marine animals that live in tropical and subtropical regions. Their body is in the form of a bag (the body size of one individual in a colony is no more than 1 mm, and single ones can reach 60 cm); there are two siphons on the body - oral and cloacal. Larval chordates are water filterers. The body is covered with a thick shell - a tunic (hence the name of the subtype - Tunicates). As adults, Tunicates lack a notochord and a neural tube. However, the larva, which actively swims and serves for dispersal, has a typical structure for Chordata and is similar to the Lancelet (hence the second name - Larval Chordates). Representative - Ascidia.
3. Subtype Vertebrates, or Cranial. These are the most highly organized chordates. Vertebrates have active feeding: food is sought and pursued.
The notochord is replaced by the vertebral column. The neural tube is differentiated into the spinal cord and brain. The skull is developed, which protects the brain. The skull bears jaws with teeth for capturing and grinding food. Paired limbs and their belts appear. Cranials have much more high level metabolism, complex population organization, diverse behavior and pronounced individuality of individuals.
The subtypes Cranial and Larval Chordates are called lower Chordates, and the subtype Vertebrates are higher Chordates.
Subtype Skullless - Acrania
Lancelet
The subtype Cephalochordates includes the only class Cephalochordates, which includes only about 30-35 species of marine animals living in shallow waters. A typical representative is Lancelet — Branchiostoma lanceolatum(genus Lancelet, class Cephalochordates, subtype Cranial, type Chordata), whose dimensions reach 8 cm. The body of Lancelet is oval in shape, narrowed towards the tail, compressed laterally. Externally, the Lancelet resembles a small fish. Located on the back of the body caudal fin in the shape of a lancet - an ancient surgical instrument (hence the name Lancelet). There are no paired fins. There is a small dorsal. On the sides of the body from the ventral side hang two metapleural folds, which fuse on the ventral side and form peribranchial, or the atrial cavity, communicating with the pharyngeal slits and opening at the posterior end of the body with an opening - atrioporom- out. At the anterior end of the body near the mouth there are perioral tentacles, with which Lancelet captures food. Lancelets live on sandy soils in the sea at a depth of 50-100 cm in temperate and warm waters. They feed on bottom sediments, marine ciliates and rhizomes, eggs and larvae of small sea crustaceans, diatoms, burying themselves in the sand and exposing the front end of their body. They are more active at dusk and avoid bright lighting. Disturbed Lancelets swim quite quickly from place to place.
Veils. The body of the Lancelet is covered skin, consisting of a single layer epidermis and thin layer dermis.
Musculoskeletal system. A chord stretches along the entire body. Chord- This is an elastic rod located on the dorsal side of the body and performs a supporting function. The chord becomes thinner towards the anterior and posterior ends of the body. The notochord protrudes into the anterior part of the body somewhat further than the neural tube, hence the name of the class - Cephalochordates. The notochord is surrounded by connective tissue, which simultaneously forms supporting elements for the dorsal fin and divides muscle layers into segments using connective tissue
Type Chordata subtype Lancelet
interlayers. The individual muscle segments are called myomeres, and the partitions between them are myoseptami. The muscles are formed by striated muscles.
Body cavity at Lanceletnik secondary, in other words, these are coelomic animals.
Digestive system. On the front of the body there is mouth opening, surrounded tentacles(up to 20 pairs). The mouth opening leads into a vast throat, which functions as a filtering apparatus. Through the cracks in the pharynx, water enters the atrial cavity, and food particles are directed to the bottom of the pharynx, where the endostyle- a groove with ciliated epithelium that drives food particles into the intestine. There is no stomach, but there is hepatic outgrowth, homologous to the liver of vertebrates. Midgut opens without making loops anus at the base of the caudal fin. Digestion of food occurs in the intestines and in the hollow hepatic outgrowth, which is directed towards the head end of the body. Interestingly, Lancelet has preserved intracellular digestion; intestinal cells capture food particles and digest them in their digestive vacuoles. This method of digestion is not found in vertebrates.
Respiratory system. Lancelet has more than 100 pairs in its throat gill slits, leading to peribranchial cavity. The walls of the gill slits are penetrated by a dense network of blood vessels in which gas exchange occurs. With the help of the ciliated epithelium of the pharynx, water is pumped through the gill slits into the peribranchial cavity and through the opening (atriopore) it is discharged out. In addition, the skin, which is permeable to gases, also takes part in gas exchange.
Circulatory system. Circulatory system of Lancelet closed. Blood is colorless and does not contain respiratory pigments. The transport of gases occurs as a result of their dissolution in the blood plasma. In the circulatory system one circle blood circulation There is no heart, and the blood moves thanks to the pulsation of the gill arteries, which pump blood through the vessels in the gill slits. Arterial blood enters dorsal aorta, from which carotid arteries blood flows to the anterior part, and through the azygos dorsal aorta to the posterior part of the body. Then by veins the blood returns to venous sinus and by abdominal aorta goes to the gills. All blood from the digestive system enters the hepatic process, then into the venous sinus. The hepatic outgrowth, like the liver, neutralizes toxic substances that enter the blood from the intestines, and, in addition, performs other functions of the liver.
This structure of the circulatory system is not fundamentally different from the circulatory system of vertebrates and can be considered as its prototype.
Excretory system. The excretory organs of Lancelet are called nephridia and resemble excretory organs flatworms- protonephridia. Numerous nephridia (about one hundred pairs, one for two gill slits), located in the pharynx, are tubes that open with one opening into the coelom cavity, and the other into the peribranchial cavity. On the walls of the nephridium there are club-shaped cells - solenocytes, each of which has a narrow canal with a ciliated hair. Due to the beating of these
Type Chordata subtype Lancelet
hairs, liquid with metabolic products is removed from the nephridium cavity into the peribranchial cavity, and from there out.
Central nervous system educated neural tube with a cavity inside. The lancelet does not have a pronounced brain. In the walls of the neural tube, along its axis, there are light-sensitive organs - Hessian eyes. Each of them consists of two cells - photosensitive And pigment, they are able to perceive the intensity of light. The organ is adjacent to the expanded anterior part of the neural tube sense of smell.
Reproduction and development. Lancelets that live in our Black Sea and Lancelets that live in the waters of the Atlantic off the coast of Europe begin breeding in the spring and spawn eggs until August. Warm water lancelets breed all year round. Lancelets dioecious, gonads (gonads, up to 26 pairs) are located in the body cavity in the pharynx. Reproductive products are excreted into the peribranchial cavity through temporarily formed reproductive ducts. Fertilization external in the water. Emerges from a zygote larva. The larva is small: 3-5 mm. The larva actively moves with the help of cilia covering the entire body and due to the lateral bends of the body. The larva swims in the water column for about three months, then moves on to life at the bottom. Lancelets live up to 4 years. Sexual maturity is reached by two years.
Meaning in nature and for humans. Anesthenes are an element of biological diversity on Earth. Fish and crustaceans feed on them. The Skullless themselves process dead organic matter, being decomposers in the structure of marine ecosystems. The skullless are essentially a living blueprint for the structure of chordates. However, they are not the direct ancestors of vertebrates. In Southeast Asian countries local residents Lancelets are collected by sifting sand through a special sieve and eaten.
Skullless animals have retained a number of features characteristic of their invertebrate ancestors:
§ excretory system of nephridial type;
§ absence of differentiated sections in the digestive system and preservation of intracellular digestion;
§ filtering method of feeding with the formation of a circumbranchial cavity to protect the gill slits from clogging;
§ metamerism (repeated arrangement) of the genital organs and nephridia;
§ absence of a heart in the circulatory system;
§ poor development epidermis, it is single-layered, like in invertebrate animals.
Type Chordata subtype Lancelet
Rice. The structure of the lancelet.
A - neural tube, chord and digestive system; B - circulatory system.
1 - chord; 2. - neural tube; 3 - oral cavity; 4 - gill slits in the pharynx; 5 - peribranchial cavity (atrial cavity); 6 - atriopor; 7 - hepatic outgrowth; 8 - intestine; 9 - anus; 10 - subintestinal vein; 11 - capillaries of the portal system of the hepatic outgrowth; 12 - abdominal aorta; 13 - pulsating bulbs of arteries pumping blood through the gill slits; 14 - dorsal aorta.
Rice. Nephridium Lancelet.
1 - opening as a whole (into the secondary body cavity); 2 - solenocytes; 3 - opening into the peribranchial cavity.
Type Chordata subtype Lancelet
Rice. Cross section of Lancelet:
A – in the pharynx area, B – in the midgut area.
1 - neural tube; 2 - muscles; 3 - roots of the dorsal aorta; 4 - ovary; 5 - endostyle; 6 - abdominal aorta; 7 - metapleural folds; 8 - peribranchial (atrial) cavity; 9 — gill slits (due to the oblique position, more than one pair of them is visible on one cross section); 10 - nephridia; 11 - whole; 12 - ventral (motor) spinal nerve; 13 - dorsal (mixed) nerve; 14 - chord; 15 - subintestinal vein; 16 - dorsal aorta; 17 - dorsal fin.
Questions for self-control.
Name the characteristic features of animals of the Chordata type.
Name the classification of the type into three subtypes.
Name the systematic position of Lancelet.
Where does the Lancelet live?
What body structure does Lancelet have?
How does the Lancelet feed and what is the structure of the Lancelet's digestive system?
How does Lancelet excrete waste products?
What is the structure of the nervous system of Lancelet?
What is the structure of the circulatory system of Lancelet?
How does Lancelet reproduce?
What is the significance of Lancelet in nature?
DRAWINGS THAT NEED TO BE COMPLETED IN THE ALBUM
(3 pictures in total)
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Chordata
Chordata are the highest type of deuterostome animals. All species of this type are characterized, at least at the stage of embryonic development, by the presence of an unsegmented dorsal skeletal axis (notochord), a dorsal neural tube, and gill slits.
Phylum Chordata. General characteristics. Structural features
The phylum is divided into three subphyla: tunicates, tunicates and vertebrates.
Tunicates (Tunicata) or larval chordates (Urochordata) have a sac- or barrel-shaped body ranging from 0.3 to 50 cm in length; the size of a colony of pyrosomes can exceed 30 m. The body of tunicates is enclosed in a gelatinous tunic secreted by the outer epithelium.
The pharynx is penetrated by gill slits. The hindgut and ducts of the gonads open into the atrial cavity, which connects with the external environment. The nervous system consists of a ganglion located between the mouth and the atriopore, with a nerve trunk extending from it; sense organs are poorly developed.
Tunicates reproduce sexually; Asexual reproduction also occurs. All larval chordates are marine animals that feed on algae, small animals and detritus.
In contrast to the simplified structure of adult forms leading a sedentary lifestyle, the larvae are active, have developed sensory organs and a nervous system, muscles and notochord (in adult forms it remains only at the appendiculars). It is believed that vertebrates evolved from neotenic (began to reproduce) tunicate larvae. Three classes: tiny primitive appendicularia (Appendicularia), ascidians (Ascidiacea) and pelagic tunicates (Thaliacea), including three subclasses: pyrosomes, salps and barrel tunicates.
About 3000 species, mainly in the upper layers of seas and oceans.
Cranials (Acrania) or cephalochordates (Cephalochordata) are a subphylum of lower chordates.
The head is not separate, the skull is missing (hence the name). The entire body, including some internal organs, is segmented. Respiratory organs - gills. Blood moves due to the pulsating abdominal vessel. The sense organs are represented only by sensory cells.
The subphylum includes two families (about 20 species), whose representatives live in temperate and warm seas; The most famous is the lancelet.
Vertebrates (Vertebrata) or cranial animals (Craniota) are the most highly organized group of animals.
Vertebrates are inferior, for example, to insects in terms of the number of species, but they are very important for the modern biosphere, since they usually complete all food chains.
Due to the presence of a complex nervous system and the ability to live in a wide variety of conditions, vertebrates were divided into sharply different systematic groups and managed to achieve not only high perfection in morphology, physiology and biochemistry, but also the ability to higher forms behavior and mental activity.
The main features of vertebrates: the presence in the embryo of a notochord, which transforms into a spine in an adult animal, an internal skeleton, a separate head with a developed brain protected by a skull, perfect sensory organs, developed circulatory, digestive, respiratory, excretory and reproductive systems.
Vertebrates reproduce exclusively sexually; most of them are dioecious, but some fish are hermaphrodites.
The first vertebrates appeared in the Cambrian. 8 classes, combined into 2 superclasses: jawless (Agnatha) - shield and cyclostomes and gnathostomata (Gnathostomata) - armored, cartilaginous and bony fish, amphibians, reptiles, birds, mammals. Shield fishes, as well as armored fishes, became extinct in the Paleozoic. Currently, about 50,000 species of vertebrates are known.
General characteristics of the chordate type
Basic terms and concepts tested in exam paper: skullless, gill slits, internal skeleton, amphibians, skin, limbs and limb girdles, circulatory circles, lancelet, mammals, neural tube, vertebrates, reptiles, birds, reflexes, adaptations to lifestyle, fish, bony skeleton, cartilaginous skeleton, notochord .
TO phylum Chordata These include animals that have an internal axial skeleton—notochord or vertebral column.
In the process of evolution, chordates reached the highest level of organization and flourishing, compared to other types. They live in all areas of the globe and occupy all habitats.
Chordata- These are bilaterally symmetrical animals with a secondary body cavity and a secondary mouth.
In chordates, there is a general plan of the structure and location of the internal organs:
– the neural tube is located above the axial skeleton;
– there is a chord under it;
– the digestive tract is located under the notochord;
– under the digestive tract is the heart.
In the phylum Chordata, there are two subtypes - Cranial and Vertebrate.
Refers to the skullless lancelet. All other chordates known today, considered in school course biology, belong to the subphylum Vertebrates.
The subtype Vertebrates includes the following classes of animals: Fish, Amphibians, Reptiles, Birds, Mammals.
General characteristics of chordates.Skin vertebrates protect the body from mechanical damage and other environmental influences.
The skin is involved in gas exchange and removal of decay products.
Derivatives of the skin are hair, claws, nails, feathers, hooves, scales, horns, needles, etc. Sebaceous and sweat glands develop in the epidermis.
Skeleton, representatives of the chordate type can be connective tissue, cartilaginous and bone. The skullless have a connective tissue skeleton. In vertebrates – cartilaginous, osteochondral and bone.
Musculature– divided into striated and smooth.
Striated muscles are called skeletal muscles. Smooth muscle forms the muscular system of the jaw apparatus, intestines, stomach and other internal organs. Skeletal muscles are segmented, although less so than in lower vertebrates. Smooth muscle has no segmentation.
Digestive system represented by the oral cavity, pharynx, always associated with the respiratory organs, esophagus, stomach, small and large intestines, digestive glands - liver and pancreas, which develop from the wall of the anterior intestine.
During the evolution of chordates, the length of the digestive tract increases, and it becomes more differentiated into sections.
Respiratory system formed by gills (in fish, amphibian larvae) or lungs (in terrestrial vertebrates).
For many, the skin serves as an additional respiratory organ. The gill apparatus communicates with the pharynx. In fish and some other animals it is formed by gill arches on which gill filaments are located.
During embryonic development, the lungs are formed from intestinal outgrowths and are of endodermal origin.
The circulatory system is closed. The heart consists of two, three or four chambers. Blood enters the atria and is sent into the bloodstream by the ventricles.
There is one circulation (in fish and amphibian larvae) or two (in all other classes). The heart of fish and amphibian larvae is two-chambered. Adult amphibians and reptiles have a three-chambered heart. However, in reptiles an incomplete interventricular septum appears. Fish, amphibians and reptiles are cold-blooded animals.
Birds and mammals have a four-chambered heart. These are warm-blooded animals.
Blood vessels are divided into arteries, veins and capillaries.
Nervous system ectodermal origin. It is laid in the form of a hollow tube on the dorsal side of the embryo. The central nervous system is formed by the brain and spinal cord. The peripheral nervous system is formed by the cranial and spinal nerves and interconnected ganglia along the spinal column.
Spinal cord is a long cord lying in the spinal canal. The spinal nerves arise from the spinal cord.
Sense organs well developed. Proto-aquatic animals have organs side line, perceiving pressure, direction of movement, speed of water flow.
Excretory organs in all vertebrates they are represented by the kidneys. The structure and mechanism of functioning of the kidneys changes during evolution.
Reproductive organs. Vertebrates are dioecious.
The gonads are paired and develop from the mesoderm. The reproductive ducts are connected to the excretory organs.
Superclass Pisces
Fish appeared in the Silurian - Devonian from jawless ancestors.
There are about 20,000 species. Modern fish are divided into two classes - Cartilaginous And Bone. Cartilaginous fish include sharks and rays, characterized by a cartilaginous skeleton, the presence of gill slits, and the absence of a swim bladder.
Characteristics of the type Chordata
Bony fish include animals that have bony scales, a bony skeleton, and gill slits covered by an operculum. The appearance of fish is due to the following aromorphoses :
– the appearance of a cartilaginous or bone spine and skull, covering the spinal cord and brain on all sides;
– appearance of jaws;
- the appearance of paired limbs - ventral and pectoral fins.
All fish live in water and have a streamlined body, divided into a head, body and tail.
Well developed sense organs - vision, smell, hearing, taste, lateral line organs, balance. The skin is two-layered, thin, mucous, covered with scales. The muscles are almost undifferentiated, with the exception of the muscles of the jaws and the muscles attached to the gill covers of bony fishes.
Digestive system well differentiated into departments.
There is a liver with a gallbladder and a pancreas. Many have developed teeth.
Respiratory organs fish are gills, and lungfish have gills and lungs. An additional function of respiration is performed by the swim bladder in bony fish. It also performs a hydrostatic function.
Circulatory system closed. One circle of blood circulation. The heart consists of an atrium and a ventricle.
Venous blood from the heart flows through the afferent gill arteries to the gills, where the blood is saturated with oxygen. Arterial blood flows through the efferent gill arteries into the dorsal aorta, which supplies blood to the internal organs.
Fish have a portal system of the liver and kidneys, which ensures the purification of the blood from harmful substances. Fish are cold-blooded animals.
Excretory system represented by ribbon-shaped primary buds. Urine flows through the ureters into the bladder. In males, the ureter is also the vas deferens.
Females have an independent excretory opening.
Sex glands represented by paired testes in males and ovaries in females. Many fish exhibit sexual dimorphism. Males are brighter than females, attracting them with their appearance and mating dances.
In the nervous system The development of the diencephalon and midbrain should be noted.
Most fish have a well-developed cerebellum, which is responsible for coordinating movements and maintaining balance. The forebrain is less developed than in higher classes of animals.
Eyes They have a flat cornea and a spherical lens.
Hearing organs represented by the inner ear - the membranous labyrinth. There are three semicircular canals.
They contain limestone stones. Fish make and hear sounds.
Organs of touch represented by sensory cells scattered throughout the body.
Side line perceives the direction of flow and water pressure, the presence of obstacles, and sound vibrations.
Taste cells are located in the oral cavity.
The importance of fish in nature and human life. Consumers of plant biomass, consumers of the second and third orders; sources food products, fats, vitamins.
EXAMPLES OF TASKS
Part A
Skullless animals include
3) lancelet
4) octopus
A2. The main characteristic of chordates is
1) closed circulatory system
2) internal axial skeleton
3) gill breathing
4) striated muscles
A3. Has a bony skeleton
1) white shark 3) stingray
2) katran 4) piranha
A4. Warm-blooded animals include
1) whale 2) sturgeon 3) crocodile 4) toad
Bony gill covers are present in
1) dolphin 3) tuna
2) sperm whale 4) electric stingray
Has a four-chambered heart
1) turtles 2) pigeons 3) perches 4) toads
1) single-chamber heart and two circles of blood circulation
2) two-chambered heart and one circulation
3) three-chambered heart and one circulation
4) two-chambered heart and two circles of blood circulation
A8. Cold-blooded animals include
1) beaver 3) squid
2) sperm whale 4) otter
Coordination of fish movements is regulated
1) forebrain 3) spinal cord
2) midbrain 4) cerebellum
A10. Doesn't have a swim bladder
1) katran 2) pike 3) perch 4) sturgeon
Part B
B1. Choose the correct statements
1) fish have a three-chambered heart
2) the transition of the head to the body in fish is clearly visible
3) the lateral line organs of fish have nerve endings
4) the notochord in some fish remains throughout life
5) fish are not capable of forming conditioned reflexes
6) the nervous system of fish consists of the brain, spinal cord and peripheral nerves
Select signs related to skullless animals
1) the brain is not differentiated into sections
2) the internal skeleton is represented by a chord
3) excretory organs - kidneys
4) the circulatory system is not closed
5) the organs of vision and hearing are well developed
6) the pharynx is penetrated by gill slits
VZ. Establish a correspondence between the characteristics of animals and the type to which these animals belong
Part C
Where can deep-sea fish store oxygen? Why do they need to do this?
C2. Read the text carefully. Indicate the numbers of sentences in which errors were made. Explain and correct them.
1. The chordate phylum is one of the largest in terms of the number of species in the animal kingdom. 2. The internal axial skeleton of all representatives of this type is the notochord - a bony, dense, elastic cord 3. The type Chordata is divided into two subtypes - Vertebrates and Invertebrates.
4. In the nervous system, the anterior part of the brain receives the greatest development. 5. All chordates have radial symmetry, a secondary body cavity, and a closed circulatory system. 6. An example of primitive chordates is the lancelet.
Chordates include about 40 thousand different species of individuals, differing from others in structure, lifestyle, and habitat.
The Paleozoic era contributed to the emergence of this type of animal approximately 500 million years ago. Scientists suggest that their ancestors were annelids.
Chordates settled throughout the planet and became habitual inhabitants of the sea, land, air and even soil.
What is a chord and who are chordates?
The internal structure of chordates is different from others. They are characterized by the presence of an axial skeleton - the vertebral column, which is otherwise called the notochord.
It was this feature of the structure of the spine that gave the name to chordates.
Structural features
The following features are characteristic of chordates:
- The location of the neural tube above the axial skeleton and the formation of the spinal cord from it.
- The presence of a rod - a chord.
- Absence of intestines in the caudal region.
- Location of the heart under the digestive tract.
Phylum Chordata - examples of animals
Representatives of chordates:
Origin and evolution of chordates
Biology as a science considers the origin of chordates to be one of the most important stages in the development of the historical animal world.
The emergence of this type meant the emergence of new animals with a unique structure, which allowed them to further evolve into creatures with maximum complexity in structure and behavior.
Some scientists believe that chordates began to exist even before the appearance of annelids, which were fed by filtration. Other scientists attribute them to the ancestors of chordates.
One way or another, the evolution of annelids, or, as they are also called, benthic worm-like animals, gave birth to new types: echinoderms, pogonophorans, hemichordates and chordates.
Subsequently, chordates evolved in three directions, depending on their lifestyle:
- The habitat of individuals of the first direction was hard ground. This contributed to the active development of the filtering apparatus, which provides nutrition during a sedentary lifestyle, and the formation of a thick protective shell over the entire surface of the body. These individuals have the ability to reproduce asexually. This is how tunicates appeared.
- The habitat of individuals of the second direction is the bottom. They moved a little more, digging into the ground. This lifestyle simplified their original organization. The development of the myochordal complex required increased mobility, and the growth of the pharynx added new gill slits. This branch has survived to this day in the form of the skullless.
- The habitat of individuals of the third direction, which began to lead a floating lifestyle, is fresh water. There was a transition to active nutrition and increased mobility. The nervous system and sensory organs became more sophisticated, which led to more complex behavior and the emergence of more complex forms. This is how a group of vertebrates appeared.
In rivers and other fresh waters, jawless ones also formed, from which jawed ones later separated. They expanded their habitat to salt water and became the progenitors of modern groups fish
Later, amphibians separated from fish. Then they came onto land, and thus appeared new look- reptiles.
General characteristics of the type Chordata
The cover consists of two layers of leather. The top layer is represented by the epidermis and its derivatives: scales, feathers, wool, hair. This layer of skin contains scent glands that produce mucus and sweat. The bottom layer is the dermis, consisting of fibrous connective tissue.
The musculoskeletal system is presented in the form of a skeleton, consisting of a chord and connecting tissues of the membrane. The skeleton of the head is divided into the brain and facial parts.
Fish develop jaws, and vertebrates develop two pairs of limbs. Bones are connected by joints.
The respiratory system in lower chordates is represented by gills, and in vertebrates by lungs. In addition, the skin of chordates is partially involved in gas exchange.
The digestive system of cephalochordates is a straight tube and almost undeveloped digestive glands. In vertebrates, this is the digestive canal, which has sections.
Food first enters the oral cavity, then passes into the pharynx, begins to be processed in the esophagus, passes into the stomach and finally enters the intestines. In addition to the listed organs, vertebrates have a liver and pancreas.
The circulatory system is closed. In vertebrates, due to an increase in metabolic rate, the heart appeared and became more complex. Cephalochordates do not have a heart.
In birds, the heart differs from the heart of reptiles only in the presence of a complete septum and the absence of the left aortic arch; Mammals have a four-chambered heart that pumps two types of blood: arterial and venous.
The central nervous system (CNS) of chordates has the form of a neural tube with an internal canal, which in vertebrates forms the brain. The peripheral nervous system includes the cranial and spinal nerves that arise from the central nervous system.
The excretory system of all chordates, except lancelets, is represented by paired kidneys, ureters and a bladder.
Reproductive system: reproduction occurs using testes in males and ovaries in females. Tunicates are hermaphrodites; they reproduce sexually and asexually. Other chordates have sexual division.
Classification of chordates and their subtypes
Chordates are divided into lower (lamprey, lancelet, hagfish) and higher (reptiles, amphibians, fish, birds, mammals).
The following subtypes are distinguished:
- skullless;
- tunicates;
- jawless;
- primary: classes of fish;
- tetrapods: classes of amphibians or amphibians, reptiles or reptiles, birds, mammals.
What characteristics of chordates does a person have?
In humans, like chordates, in the early stages of development, the formation of the axial skeleton, i.e., the notochord, occurs. The musculoskeletal system in humans is represented, as in vertebrates, by the supporting internal skeleton.
Humans also have the following characteristics of chordates:
- central nervous system, which has a tubular structure;
- a closed circulatory system with the main circulatory organ - the heart;
- a breathing apparatus capable of communicating with the external environment through the pharynx, nasal cavity and mouth.
Monkey eel
Some interesting information:
The importance of chordates is very great; they are classified among the most diverse and numerous types. At the moment, there are about 50 thousand species of chordates. The presence of a common feature in all individuals - the notochord (supporting organ) - gave the name to this type of animal.
The anatomical features of chordates are similar to echinoderms. The lowest representatives of chordates are lancelets, which retain their main character throughout their lives.
The phylum Chordata unites animals that differ in appearance, living conditions, and lifestyle. Representatives of this type are found in all major environments of life: in water, on land, in the soil, in the air. They are distributed throughout the Earth. The number of species of modern representatives of chordates is about 40 thousand.
The phylum Chordata includes skullless, cyclostomes, fish, reptiles, amphibians, mammals and birds. Tunicates can also be classified as this type - this is a unique group of organisms that lives on the ocean floor and leads an attached lifestyle. Sometimes gastrobreathers, which have some characteristics of this type, are included in the phylum Chordata.
Characteristics of the type Chordata
Despite the great diversity of organisms, they all have a number of common structural and developmental features.
The structure of chordates is as follows: all these animals have an axial skeleton, which first appears in the form of a notochord or dorsal string. The notochord is a special non-segmented and elastic cord that embryonically develops from the dorsal wall of the embryonic intestine. The origin of the chord is endothermal.
Further, this cord can develop differently, depending on the organism. It remains throughout life only in lower chordates. In most higher animals, the notochord is reduced, and in its place a vertebral column is formed. That is, in higher organisms, the notochord is an embryonic organ that is replaced by vertebrae.
Above the axial skeleton is the central nervous system, which is represented by a hollow tube. The cavity of this tube is called a neurocoel. Almost all chordates are characterized by a tubular structure of the central nervous system.
In most chordate organisms, the anterior section of the tube grows to form the brain.
The pharyngeal section (anterior) of the digestive tube comes out at two opposite ends. The openings that emerge are called visceral fissures. Lower organisms of the type have gills on them.
In addition to the three above-mentioned features of chordates, it can also be noted that these organisms have a secondary mouth, like echinoderms. The body cavity in animals of this type is secondary. Chordata are also characterized by bilateral body symmetry.
The phylum Chordata is divided into subtypes:
- Skullless;
- Tunicates;
- Vertebrates.
Subtype Skullless
This subphylum includes only one class - Cephalochordates, and one order - Lancelets.
The main difference between this subtype is that these are the most primitive organisms, and all of them are exclusively marine animals. They are widespread in the warm waters of oceans and seas of temperate and subtropical latitudes. Lancelets and epigonychites live in shallow water, mainly burying the back part of their body in the bottom substrate. They prefer sandy soil.
This type of organism feeds on detritus, diatoms or zooplankton. They always breed in the warm season. Fertilization is external.
The lancelet is a favorite object of study, because all the characteristics of chordates are preserved for life, which allows us to understand the principles of the formation of chordates and vertebrates.
Subtype Tunicates
The subtype includes 3 classes:
- Salps;
- Ascidians;
- Appendiculars.
All animals of the subtype are exclusively marine.
The main difference between these chordates is that almost all organisms lack a notochord and a neural tube as adults. In the larval state, all the characteristics of the type in tunicates are clearly expressed.
Tunicates live in colonies or solitarily, attached to the bottom. There are significantly fewer free-swimming species. This subtype of animals lives in the warm waters of the tropics or subtropics. They can live both on the surface of the sea and deep in the ocean.
The body shape of adult tunicates is round, barrel-shaped. The organisms got their name due to the fact that their body is covered with a rough and thick shell - a tunic. The consistency of the tunic is cartilaginous or gelatinous; its main purpose is to protect the animal from predators.
Tunicates are hermaphrodites and can reproduce both sexually and asexually.
It is known that the ancestors of these organisms were free-swimming, but at present only tunicate larvae can move freely in the water.
Subphylum Vertebrates
Cranial animals are the highest subphylum. Compared to other subtypes, they have a higher level of organization, which is evident from their structure, both external and internal. Among vertebrates, there are no species that lead a completely attached lifestyle - they actively move in space, looking for food and shelter, and a pair for reproduction.
By moving, vertebrate organisms provide themselves with the opportunity to change their habitat depending on changing external conditions.
The above general biological features are directly related to the morphological and physiological organization of vertebrates.
The nervous system of cranial animals is more differentiated than that of lower animals of the same type. Vertebrates have a well-developed brain, which contributes to the functioning of higher nervous activity. It is the highest nervous activity is the basis of adaptive behavior. These animals have well-developed sensory organs, which are necessary for communication with the environment.
As a result of the emergence of sensory organs and the brain, a protective organ such as the skull developed. And instead of a chord, this subtype of animals has a spinal column, which serves as a support for the entire body and a case for the spinal cord.
All animals of the subtype have a movable jaw apparatus and an oral fissure, which develop from the anterior section of the intestinal tube.
The metabolism of this subtype is much more complex than that of all the animals discussed above. Cranial animals have a heart that provides rapid blood flow. Kidneys are necessary for removing waste products from the body.
The subtype Vertebrates appeared only in the Ordovician-Silurian, but in the Jurassic period all currently known types and classes already existed.
Total quantity modern species a little over 40 thousand.
Classification of vertebrates
The phylum Chordata is very diverse. The classes existing in our time are not so numerous, but the number of species is enormous.
The cranial subtype can be divided into two groups, these are:
- Primary water organisms.
- Terrestrial organisms.
Primary water organisms
Proto-aquatic eggs are distinguished by the fact that they either have gills throughout their entire life or only in the larval stage, and during the development of the egg, embryonic membranes are not formed. This includes representatives of the following groups.
Section Agnathans
- Class Cyclostomes.
These are the most primitive cranial animals. They actively developed in the Silurian and Devonian; at present, their species diversity is not great.
Section Gastrostomes
Pisces superclass:
- Class Bony fish.
- Class Cartilaginous fish.
Superclass Quadrupeds:
- Class Amphibians.
These are the first animals to develop a jaw apparatus. This includes everything famous fish and amphibians. All of them actively move in water and on land, hunt and capture food with their mouths.
Terrestrial organisms
The group of terrestrial animals includes 3 classes:
- Birds.
- Reptiles.
- Mammals.
This group is characterized by the fact that in animals, during the development of the egg, embryonic membranes are formed. If the species lays eggs on the ground, the embryonic membranes protect the embryo from external influences.
All chordates of this group live mainly on land and have internal fertilization, which suggests that these organisms are more evolutionarily developed.
They lack gills at all stages of development.
Origin of chordates
There are several hypotheses for the origin of chordates. One of them suggests that this type of organisms originated from the larvae of intestinal-breathers. Most representatives of this class lead an attached lifestyle, but their larvae are mobile. Examining the structure of the larvae, one can see the rudiments of the notochord, the neural tube and other features of chordates.
Another theory states that the phylum Chordates evolved from the crawling, worm-like ancestors of the gastrobreathers. They had the rudiments of a chord, and in the pharynx, next to the gill slits, there was an endostyle - an organ that contributed to the secretion of mucus and the capture of food from the water column.
The article discussed the general characteristics of the type. Chordates are united by many similar features of all organisms, but still each class and each species has individual characteristics.
Chordates are the highest type of animal kingdom, uniting more than 43,000 species very diverse in size, appearance and habitat. Most of them have an internal cartilaginous or bony skeleton and are called vertebrates. The structural plan of vertebrates sharply distinguishes them from animals of other types, and therefore the question of the origin of vertebrates remained unresolved for a long time. The credit for clarifying this issue belongs to the Russian embryologist A.O. Kovalevsky (1840-1901). Having studied the development of the embryos of some primitive marine animals - the lancelet and ascidians, he showed that they are transitional forms that combine the features of invertebrates and vertebrates.
Thanks to this, A. O. Kovalevsky managed to overcome the gap that separated vertebrates from the lower groups of the animal world and shed light on their origin. Currently, vertebrates, together with transitional forms, are united into a single type of chordates.
Type characteristics
Despite the diversity of species, all chordates have a common structural plan and differ from representatives of other types in the following four main characters.
- They have an internal axial skeleton, represented by a dorsal string, or chord (chorda dorsalis). The chord is an elastic flexible rod. It develops from the endoderm, consists of highly vacuolated cells and is surrounded by a connective tissue membrane. In lower chordates, it is preserved throughout life (lancelets, sturgeons, lungfishes and lobe-finned fish), in higher chordates (i.e., most vertebrates), the chord is present only in larvae or embryos, and then is replaced by a cartilaginous or bone formation - the spine . The spinal column consists of individual vertebrae, which during the process of ontogenesis are formed in the connective tissue membrane of the notochord.
- The central nervous system is located on the dorsal side above the notochord. It looks like a tube stretching along the body and has an internal cavity - a neurocele. The central nervous system develops from the ectoderm and differentiates in vertebrates into the brain and spinal cord. In all invertebrates, the nervous system is located on the ventral side of the body and is a chain of nerve ganglia connected by nerve cords.
- The digestive system is located under the notochord, it begins with the mouth and ends with the anus (anus). The anterior (pharyngeal) section of the digestive tube has a number of through holes - the gill apparatus. It is represented by gill slits that pierce the wall of the pharynx, and a skeleton that supports the gill slits (visceral arches). The gill apparatus, as well as the notochord, is not preserved in all adult animals. Gill slits are characteristic of fish throughout life and are supplemented by special organs of aquatic respiration - gills; in others they are present only in the larval state (tadpoles of amphibians); in terrestrial vertebrates, gill slits are formed in the embryo, but soon become overgrown; the air respiratory organs - the lungs - develop as paired protrusions on the ventral side of the back of the pharynx.
The notochord, neural tube and intestine stretch along the entire body and form a complex of axial organs.
- The circulatory system is closed. The central circulatory organ - the heart or a pulsating blood vessel that replaces it - is located on the ventral side of the body and is formed in the embryo under the notochord and the digestive tube.
In addition to these basic characteristics of chordates, they are very characterized by the mutual arrangement of the nervous, supporting and digestive systems. In other types of the animal kingdom there is no such strict pattern (remember the location of the corresponding systems of round and annelids, arthropods, and mollusks).
At the same time, chordates have characteristics in common with achordates. All chordates have bilateral symmetry, have a metameric organ anlage, a secondary body cavity and a secondary mouth.
The oral opening is formed by breaking through the gastrula wall. At the site of the opening of the gastrula (gastropore), an anal opening is formed. This character unites chordates, echinoderms, and several few related types into the group of deuterostomes. The remaining types discussed earlier (with the exception of unicellular ones) are combined into the group of protostomes.
The main organ systems of chordates, including the skeleton, muscles, nervous system, excretory organs, etc., are formed metamerically in embryos. Metamerism is especially pronounced in the embryonic period.
The chordate phylum is divided into 3 subphyla.
- Subphylum Tunicata (tunicates).
The first two subtypes include a small number of primitive marine animals that lead a sedentary or motionless lifestyle and lack a vertebral column. There are no tunicates in the program for entering universities. Cranials have a nervous system structure typical of chordates in the form of a neural tube, but its anterior part is not expanded and not protected by any cartilaginous or bone formation, i.e. there is no brain or skull. The skullless subtype includes one class of simply constructed animals - lancelets. These are not numerous (only about two dozen species) marine animals.
When characterizing the lancelet, pay attention to the features that make it similar to lower invertebrate animals: the absence of a brain, real sense organs and heart, the absence of paired limbs, the primitive structure of the excretory organs. On the other hand, the signs of a progressive organization should be emphasized: the presence of a true notochord and a tubular nervous system typical of chordates, as well as a closed circulatory system. The listed characteristics suggest that the lancelet and vertebrates had a common ancestor, which was probably similar to skullless animals.
The fourth subtype is the most numerous. It unites highly organized animals with a cartilaginous or bony skeleton. The anterior part of the neural tube is expanded, forming the brain, which is protected by a cartilaginous or bony skull. The part of the neural tube located in the body and called the spinal cord is enclosed together with the notochord in a cartilaginous or bony spine, consisting of individual vertebrae. There is a circulatory organ - the heart, which lies on the ventral side of the body, as well as complex kidneys. In addition, vertebrates are characterized by well-developed paired limbs (except for cyclostomes) and perfect sensory organs (vision, hearing, smell, etc.). All this provides vertebrates with high mobility, the ability to navigate in space, and easily find prey.
The vertebrate subphylum is divided into six classes: cyclostomes, fish, amphibians (amphibians), reptiles (reptiles), birds and mammals. The applicant is required to know the last five classes. Their brief description is given in table. 16.