Type Chordata - one of the largest in terms of the number of species in the animal kingdom. In total, it contains about 50 thousand modern species. Chordates appeared at the beginning of the Paleozoic, more than 500 million years ago. It is believed that they originated from some ancient annelids. Representatives of this type have common features and a single structure plan (Fig. 109).

Rice. 109. General scheme of the internal structure of a chordate animal: 1 - gill openings; 2 - blood vessels; 3 - chord; 4 - neural tube; 5 - digestive tube; 6 - anus

The internal axial skeleton is the chord - an elastic, dense and elastic cord. With the development of the embryo, the notochord is formed from the endoderm layer; it is formed in the dorsal part of the embryonic intestine. In lower chordates, it performs the role of the internal axial skeleton for life, in higher animals it functions as an axial skeleton only at the embryonic stage of development, and in adult animals it is replaced by the spine.

The central nervous system, where the nerve centers (clusters of neuron bodies) are located, in chordates is represented by the neural tube, which, during the development of the embryo, is formed from the ectoderm layer. The neural tube is located on the dorsal side above the chord. In lower chordates, it is not divided into sections, while in higher ones it is divided into the spinal cord and brain.

The anterior part of the digestive tube is the pharynx. It has gill openings and functions as a common division of the digestive and respiratory systems. In lower chordates, gills develop on the interbranchial septa, which function throughout life. In higher chordates, gill rudiments appear at certain stages of embryonic development, and lungs develop in adult animals.

In addition to these main features, chordates have other characteristic features. Chordates are deuterostome, secondary cavity, bilaterally symmetrical animals. In them, in the early stages of embryonic development, an anus is formed in the place of the primary mouth, and a secondary mouth is formed at the opposite end of the body.

Rice. 110. Representatives of chordates: 1 - bone fish (roach); 2 - amphibian (frog); 3.4 - reptiles (lizard, snake); 5 - bird (jay); 6 - mammal (wolf)

In chordates, striated muscles develop, and the head section with sensory organs separates. The circulatory system is closed; higher chordates develop a muscular pumping organ - the heart.

Such a structure of chordates turned out to be evolutionarily progressive. This allowed them to master all habitats, spread throughout the globe. Chordates are very diverse (Fig. 110) and are represented by many ecological groups, and some species of chordates reach a high abundance.

Type Chordates are divided into three subtypes. Two of them - Cranial and Cranial, or Vertebrates, are discussed in this zoology course. The Cranial subtype includes one class - Lancelets, the Cranial (Vertebrate) subtype includes the classes: Cartilaginous fish and Bony fish, Amphibians, Reptiles, Birds and Mammals.

Subtype Cranial. Lancelet

Non-cranial - marine, mainly bottom animals, retaining characteristics of the Chordata type for life. The study of these most primitive chordates is important for understanding the origin and initial stages of their evolution.

There are 30 modern species in the Lancelets class. Lancelets live in shallow waters, in the coastal part of warm seas and oceans. In our country, they are found on the shallows of the Black and Japan Seas. Most of the time these animals spend burrowing into the sand and exposing the front end of the body with a preoral funnel surrounded by tentacles. Lancelets feed on protozoa and unicellular algae.

Lancelet - primitive (Fig. 111). The dorsal fin extends along the upper side of the body. It passes into the caudal fin, which is shaped like a lancet medical instrument. For this similarity, the lancelet got its name. It was first described by the Russian academician P.S. Pallas in 1774. The lancelet has no paired fins. The skin is very thin, through them translucent internal organs.

Rice. 111. Lancelet buried in the sand

The lancelet retains for life all the signs of chordates (Fig. 112).

Rice. 112. Scheme of the internal structure of the lancelet: 1 - tentacles; 2 - preoral funnel; 3 - gill openings; 4 - neural tube; 5 - chord; 6 - peribranchial cavity; 7 - gut; 8 - anus; 9 - hepatic outgrowth

Its internal axial skeleton is represented by a chord stretching along the body. The notochord and the neural tube lying above it are surrounded by a connective tissue sheath. Numerous nerves depart from the central nervous system (neural tube) - sensitive (perceiving irritation) and motor (transmitting excitation to the muscles). Nerves form the peripheral nervous system. In the skin there are tactile cells, in the neural tube, among other nerve cells, light-sensitive eyes.

Under the notochord is the digestive tube. Its anterior part - the pharynx - has gill openings. Therefore, the pharyngeal intestine performs the functions of both the digestive and respiratory systems (Fig. 113). Gill arteries (thin blood vessels) pass through the interbranchial septa, through which oxygen enters the blood and carbon dioxide is released into the water. Gas exchange occurs due to the difference in pressure of gases that enter places with lower pressure.

Rice. 113. Scheme of the digestive and respiratory systems of the lancelet: 1 - preoral funnel; 2 - tentacles; 3 - gill openings; 4 - gut; 5 - anus; 6 - gonads

At the bottom of the pharynx is a groove lined with ciliated cells. The movements of the cilia create a stream of water that washes over the gills. Small food particles that have fallen into the pharynx are glued together and the flow of water is directed further along the digestive tube. Under the influence of digestive juices, food is digested, and undigested residues are removed through the anus.

The anterior end of the body is surrounded by a fold of skin that forms the near-gill cavity. This protects the gill slits from solid particles entering them.

The circulatory system of the lancelet is closed (Fig. 114). Through a large abdominal vessel, blood moves forward to the gills, where it is oxidized (enriched with oxygen). The dorsal aorta carries oxygenated arterial blood to all parts of the body. From them, venous blood, saturated with carbon dioxide, enters the abdominal vessel. The lancelet has no heart. Blood moves by contraction of the so-called "gill hearts" - the walls of the abdominal vessel at the base of the gill arteries.

Rice. 114. Scheme of the circulatory system of the lancelet: 1 - branchial arteries; 2 - dorsal aorta; 3 - veins; 4 - capillary network; 5 - abdominal aorta

The excretory organs are very similar to the excretory organs of annelids and are excretory tubes that open at one end into the body cavity, and at the other fall into the common canal. Several common excretory canals open into the peribranchial cavity. From here, waste products get out.

Lancelets, like most other chordates, are dioecious animals. In females, eggs are produced in the ovaries; in males, spermatozoa are produced in the testes. Fertilization is external: spermatozoa penetrate the eggs in water. Lancelets breed in the warm season, from spring to autumn.

The fertilized egg is crushed, goes through all the stages of development typical for other chordates: a single-layer, two-layer and three-layer embryo. Of the three germ layers (leaves) - ectoderm, endoderm and mesoderm - all organ systems of the lancelet are formed. The lancelet larva first swims in the water column, then sinks to the bottom and burrows into the sand, where it spends almost its entire life. Lancelets reach sexual maturity at the age of 2-3 years. In some places, lancelets accumulate in large numbers - up to 1400 individuals per 1 m2. In such areas of Southeast Asia, there has been a fishery for lancelets for more than 300 years. They are caught with fine mesh nets, eaten boiled and dried.

Subtype Cranial, or Vertebrate, - common features of the subtype

Most of the chordates belong to the cranial, or vertebrate, classes, in particular the classes Cartilaginous fishes and Bony fishes, Amphibians, Reptiles, Birds and Mammals.

Vertebrates are distinguished by a higher level of development than non-cranial ones. Their body is supported by the spine, which in adult animals replaces the notochord. The central nervous system is especially improved: the neural tube is divided into the brain and spinal cord. The sense organs are well developed. A skull has developed to protect the brain. Paired limbs are formed: in fish - paired fins, in terrestrial vertebrates - five-fingered limbs. Unlike non-cranial vertebrates, a muscular heart appears in the circulatory system. The excretory organs are the kidneys. Vertebrates lead an active lifestyle, sometimes making distant migrations. They have mastered all habitats and are distributed throughout the globe. Many species of vertebrates reach high numbers.

The Chordata phylum includes non-cranial and cranial (vertebrate) animals. One of the most primitive representatives of chordates is the lancelet, which retains all their main features throughout life: the notochord serves as the axial skeleton, the neural tube is the central nervous system, and the pharynx has gill openings. The lancelet is a dioecious animal that is characterized by external fertilization. The cranial are at a higher level of development than the non-cranial.

Lesson learned exercises

1. What are the subtypes of the chordate type? Name the representatives of these subtypes.
2. Using the example of the lancelet (see Fig. 113), tell us about the features of the internal structure of chordates.
3. What is the importance of lancelets?
4. What is the complication of the structure of chordates in comparison with invertebrates, such as annelids?

1. Type Chordates

Chordates are divided into lower (Cranial and Tunic) and higher (Vertebrates).

Typical signs of chordates:

1) the presence throughout life or 1 of the period of the dorsal string - a chord that 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, it is connected by a neuropore to the external environment. The neural tube lies above the chord, 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 pierced by gill slits, in water gills appear in their place, in terrestrial ones, lungs appear as protrusions of the pharyngeal wall.

4) the circulatory system is in the form of a tube, the heart is located on the ventral side under the chord and digestive tube.

Features that unite with invertebrates:

Secondority, is formed by breaking through the wall of the gastrula. In place of the gastropore, a posterior opening is formed.

The secondary cavity of the body - the whole

The presence of metamerism - the segmental arrangement of organ systems

Bilateral, bilateral symmetry

Subtype Cranial

Origin:

According to A.N. Severtsov, the ancestors of the non-cranial 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, near-bottom or burrowing lifestyle. Subsequently, some non-cranial animals moved to life in the bottom soil, they developed metallural folds and a peribranchial (atrial) cavity (lancelets and epigonichths). The other part remained to live in the water column (amphioxides).

Systematics. Class Cephalothordates

Sem. Brachiostomy- lancelets (European, Asian)

Sem. Amphioxide- signs of larvae are characteristic, 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 region of the back it is called the dorsal fin, which passes into the caudal fin, then into the caudal fin, metapleural folds pass along the gods of the body, they merge with the caudal folds. The skin of the lancelet consists of 2 layers:

Single layer epidermis (unicellular glands, f mucus - protective)

Thin gelatinous connective tissue - cutis, or corium

Muscular system: 50-80 segments are adjacent to the chord - myomers. The segments are separated by myoseptae (septa).

CNS: There is only a chord in the head. The neurocoel is the rudiment of the ventricle of the brain. In larvae, it communicates with the external environment through the neuropore. In adults, in place of the neuropore - the fossa of Kelliker - the organ of smell. The spinal 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 pierced by gill slits. They breathe oxygen dissolved in water. At the bottom of the pharynx there is a groove - endostyle, on which there is a glandular and ciliary epithelium: it secretes a large amount of mucus. The intestines are in the form of a straight tube, ending with an anus.

excretory system: Nefridial. In the anterior part above the pharynx lies about 100 pairs of nephridia (a short strongly curved tube with holes).

Reproduction: Dioecious. There are sex glands. Females have ovaries, males have testes. There are no genital ducts. Mature germ cells enter the atrial cavity through cell ruptures. Fertilization is external, the development of the egg in water.

2. Subtype larval-chordata (tunicates)

Tunicates are a branch of chordates. All typical signs of chordates are developed only in the larval stage. Some species lead a sedentary lifestyle, while others move slowly in the water column. All marine animals feed passively by filtering water flows. Hermaphrodites. Asexual reproduction by budding. The circulatory system is of an open lacunar type.

Ascidia class. 3 Squads:

Neg. solitary sea squirts- gastroascidia or spherical.

Neg. Synascidia, or Colonial- colonies are connected with other bases, united by a common tunic, have independent oral siphons. Fertilization is possible between different colonies.

Neg. Pyrosomats, or Firemen- 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) hard cuticle outside, under the cuticle - a fibrous network impregnated with tunicin (methane-like substance.

2) two-layer mantle, or musculoskeletal sac: 1. layer - epithelium, skin, two-layer. 2. transverse muscle fibers.

Digestive system, nutrition: Mouth → huge pharynx (gill openings - stigmas; endostyle). The pharynx is a respiratory organ. There is a heart - tubular, the edges are reduced alternately, creating a pendulum-like movement of blood.

Organs of excretion and reproduction: renal vesicles, throughout life there is an accumulation of urea crystals. Sex cells enter the water through the cloacal siphon. They are captured 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 breaks the egg membranes → goes out into the environment. Swimming 2-3 hours. attached to the substrate → regressive metamorphosis.

Salpa class- floating, sea.

Neg. True salps- colonies exist for a short time.

Neg. kegs- polymorphic colonies

Outwardly, the body resembles a cucumber or a barrel, dressed in muscular ribbons. The entire body is occupied by the atrial and pharyngeal cavities, separated by a dorsal outgrowth. The successive contraction of the muscle bands from the anterior end of the body drives water from the pharynx into the atrial cavity and pushes it out with force → the salpa jerkily moves forward. Salps are characterized by alternation of sexual and asexual reproduction - metagenesis. The asexual salpa develops from the fertilized egg. A kidney stolum is formed 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. Sperm enters the cloacal siphon and fertilizes the egg there. The egg matures in the ovary, breaks the egg shells and comes out. The mother's body dies. The fetus is growing.

Appendicular class- floating. A small oval body from which a tail extends. 1 pair of gill openings. From the base to the tail stretches the chord, neural tube, muscle cords. There is no real tunic. The ectodermal cells of the mantle secrete mucus with a chitin-like substance. With the movement of the tail, the mucus is knocked into a kind of house. Opposite the oral siphon, a lattice of thickened threads of mucus is built. With a blow of the tail, he breaks the house and leaves it. Floats for a while. Builds a new house in 2 hours.

Development and reproduction: In sexually developed individuals, the spermatozoa come out. Eggs mature in the ovary. Sperm enters the ovary, fertilization occurs. An embryo is formed in the eggs, it grows, leaves the mother's body. Comes out. It looks like an adult, differs only in size.

3. Subtype Vertebrate or Cranial

The main features of the organization of vertebrates

Body Shape: In aquatic vertebrates, the body is divided into the head, trunk, and tail. Terrestrials have a variety of body shapes. The cervical region appears, the mobility of the head increases. Unpaired fins are reduced, paired ones turn into limbs. In aquatic limbs, they again turn into fins.

Skin covers: two-layer skin: 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 chord is replaced by the vertebral column. The spinal column is differentiated, the cervical, thoracic, lumbar, sacral, caudal regions appear.

skull skeleton: The medulla closes the brain. On the sides of the chord, parachordalia are formed, in front of the lateral cartilages and trabeculae. In bony fish, the skull remains cartilaginous, and a shell forms on top. In bony bones, ossification occurs, 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 brain skull:

1) protostyle - the jaw and hyoid arches are suspended from the skull (primitive maxillary)

2) hyostylia - 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. Water has a segmental structure (metomeric). With the transition to the ground image, ribbon-like 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 dorsal. In the anterior part, 3 brain bubbles are formed: anterior, middle, posterior. Further differentiation leads to the formation of 5 departments. From the anterior part of the anterior cerebral bladder, the brain is formed. The back of the anterior cerebral bladder turns into the diencephalon. There are 12 pairs of cranial nerves. Aquatic - 10.

Sense organs: Vision - twin eyes. Organs of hearing: anatomically connected with the organ of balance. In higher, the spiral coiled canal (cochlea) is the organ of hearing. The organs of smell are immersed in the skin. The organs of taste: taste buds are an accumulation of sensitive and supporting cells. In fish on the fins, in others in the mouth.

Digestive system: Starting with the ancient jaws, the oral apparatus is sucking, in modern cyclostomes it is a suction funnel, in fish, a mouth apparatus armed with teeth is being formed. At the bottom of the oral cavity, a tongue with its skeleton (sublingual apparatus) is formed. In the oral mucosa scattered taste buds. The pharynx in aquatic is permeated with gill slits, in terrestrial ones the lungs are connected with it. Pharynx-esophagus-stomach. Sections of the stomach: the cardial part (the esophagus empties), the bottom or fundus part, the pilar intestine (differentiates). Intestines: large intestine, small intestine, rectum. It ends either in the cloaca or the anus.

Respiratory system: Gill slits develop in aquatic animals, gill sacs develop in jawless fish, gill filaments develop between gill slits, which together make up gills. The main function is gas exchange. Amphibians have respiratory organs - lungs.

Circulatory system: Skullless - closed. The heart first appears in cyclostomes as an expansion of the abdominal aorta. First, the heart is 2-chambered. Further 3-chamber (amphibians, reptiles). Starting with amphibians - 2 circles of blood circulation: small and large.

excretory system:

Vertebrate larvae develop a pronephros or pronephros. It is represented by a collection of nephridia. The main element of the kidney is the Malpighian bodies. Amniotes develop pelvic buds (metanephros).

reproductive system: Most are dioecious. The ovaries have a granular structure, the testes are smooth. For anamnia, external fertilization is characteristic, in some internal. Eggs develop only in the aquatic environment. There is a live birth. In amniotes, embryonic membranes appear, the amount of yolk increases. Development is not in the aquatic environment.

4. Section Jawless (class Cyclostomes)

The most ancient primitive vertebrates. They reached their heyday in the Silurian-Devonian. By the end of the Devonian, most of them died out. their remains have not been found. Groups of modern jawless appeared in the Carboniferous.

class cyclostomes

Includes modern jawless. 2 subclasses. The most ancient class. Representatives (lampreys, hagfishes) are characterized by a worm-like shape, bare mucous skin, a mouth opening in the depth of the suction funnel, no jaws, a cartilaginous visceral skeleton, an axial chord covered with a thick mucilaginous membrane - a fatty cushion that covers the spinal cord. Respiratory organs - gill bags (5-16 pairs). They live in the seas and fresh waters. There are unpaired fins.

P / cl. Lampreys

1Neg. Lampreys- 3 groups are distinguished by habitat:

1) Marine or anadromous lampreys- live in the seas. They go to rivers to spawn. Representatives: Atlantic, Caspian.

2) river lamprey- Inhabit coastal areas of the seas. Spawning in rivers. Representatives: European river, Japanese.

3) Impassable river, lake, stream lampreys- small, live in one place all their lives, do not migrate.

P / cl. Mixins– incl. 2 groups

Mixin group- Gill sacs flow into the common subcutaneous canal, which opens outwards with 1 opening.

Bdelostoma group- each gill sac opens outward. 5 to 16 gill sacs.

Unpaired fins. The caudal fin is equal-bladed, there are 2 dorsal fins. In females, an anal fin develops before spawning. The hagfish do not have developed dorsal fins.

covers: the epidermis is multi-layered, numerous skin cells lie in it, secrete abundant mucus (protection).

Skeleton and muscular system: Myochordal complex There is a notochord. The skull is not formed, is at an evolutionary stage, surrounds the brain only from below and from the sides. Visceral skeleton: consists of 3 sections:

a) The skeleton of the preoral funnel - elasticity

b) Gill skeleton - closes the toad sacs

c) Pericardial cartilage - clothes the heart.

The muscular system consists of muscle segments - myomers, separated from each other by partitions - myoseptae.

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 → pharynx → breathing tube → internal openings of gill sacs → 7 pairs of gill sacs → external openings of gill sacs on the side walls of the body. At the mixin: Oral opening → pharynx → independent openings of gill sacs (5-16 pairs) → gill sacs → gill canal opening outwards.

Circulatory system: Closed, 1 circle of blood circulation. There is a 2-chambered heart, 1 atrium and 1 ventricle. Hematopoiesis is carried out in the walls of the esophagus and intestines, in the kidneys, liver.

excretory system: Excretory organs - paired mesonephric (trunk) kidneys located on the dorsal side of the body above the gonads

Reproductive system and reproduction: Separate sexes. The sex glands are paired (ovary or testis), occupy almost the entire abdominal cavity of the body. There are no sexual ducts. Fertilization is external. Lamprey eggs are small. die after spawning and fertilization. They breed once in a lifetime. The larva is a sandworm. After 4-5 years, metamorphosis occurs, the gerbil turns into an adult lamprey. Hagfish have large eggs, development without metamorphosis, a young individual hatches from the egg, differing from the adult only in size. Polycyclic.

Nervous system: The head of the brain is small, lies in the same plane. 5 parts of the brain lie without leaning on each other. The medulla oblongata passes into the spinal cord.

Sense organs: Chemical sense organ: nasohypophyseal sac: Unpaired nostril → nasal passage → olfactory capsule - pituitary outgrowth. Lateral line organ - perception of water currents, registration of the approach of objects. There are weak electrical organs, temperature, tactile receptors and chemoreceptors.

5. Section Jaws. Superclass Pisces. Class Cartilaginous fish

Their earliest fossil remains in the form of scales were found in the Upper Silurian deposits. Representatives of very diverse groups are already found in the Devonian deposits. 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 and then became extinct. Another group were small freshwater acanthodia whose body was covered with bone plates. Actually cartilaginous fish known from the late Silurian - early Devonian. Lamellarbranchs survived two bursts of adaptive radiation - in the Silurian - Devonian and in the early Mesozoic. From the end of the Mesozoic, modern families of this subclass took shape.

External structure: Marine. Torpedo body. paired fins appear: pectoral, ventral. The skin is naked or covered with placoid scales. The function of the axial skeleton is performed by the spinal column. The skull is giostelic. 5-7 pairs of gill slits open on the sides of the body. In whole-headed they are covered by a common gill cover. An arterial cone develops in the heart, and a 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 spike lying on it. The main substance is dentin, covered with enamel, the cavity is the pulp, vessels and nerves - such scales are placoid.

Skeleton and muscular system: The skeleton is cartilaginous. The skeleton consists of sections: skull, axial skeleton, free fin skeleton, fin girdle. The axial skeleton is represented by the vertebral column: 2 sections - trunk and tail. The vertebrae are amphicoelous (biconcave). The skull consists of 2 sections - cerebral and visceral. The medulla consists of the olfactory and auditory capsules, the rostrum (snout), and the orbit. Visceral - consists of 3 arches: gill, hyoid, jaw. Musculature consists of myosepts,. A characteristic feature is the autonomy of the muscles - the muscles can contract with a violation of the central nervous system.

Digestion and nutrition: Predators and filtrates. rectal gland (reservoir for the accumulation of salts). Large, three-lobed liver (up to 25% of body weight), source of vitamin A.

Respiratory system: 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, passes into the external gill slits. When you exhale, the gill arches approach each other, water is pushed out.

Circulatory system: The heart consists of a venous sinus, atrium, ventricle, abdominal aorta, it begins with an arterial cone. For the first time, the spleen appears, which lies near the stomach and performs the function of a blood depot, is a hematopoietic organ.

The organs of excretion - the kidneys (trunk), in the form of ribbon-like bodies lie immediately under the spinal column.

reproductive system: Dioecious, fertilization is internal. Males: testes - vas deferens - renal tubules - Wolffian canal - cloaca - female reproductive tract. The eggs are large, covered with a horn-like shell.

CNS: Brain - 5 departments: anterior, posterior, oblong, middle, intermediate. The medulla oblongata passes into the spinal cord. 10 cranial nerves leave 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, holes. Ampoules of Lorenzini - allows you to find prey. Eyes with a large crystal, fixed eyelid. Organs of hearing: only the inner ear.

Systematics

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. Polygills

Neg. Miscellaneous

Neg. Lamellae:Sem. fox sharks, Sem. Herring, Brownie shark

Neg. Carchariform or sawtooth:Sem. Giant, Sem. Grey, Sem. feline

Neg. Catranoid (spiny) sharks

Neg. Sawtoothed

Neg. Squatinous or sea angels

N/neg. stingrays

Neg. Sawfish (sawfish)

Neg. Rough-like

Neg. Diamond-shaped or diamond-shaped slopes

Neg. Eaglet or stingray:Sem. Orlyaki, Sem. horned rays

Neg. Gnus-like or electric rays

2) P/Cl. Whole-headed- the body is valky, skin ossifications - gill covers are developed. The skull is autostylic. Teeth merge into dental plates. The interbranch septa are reduced. Neg. Chimera The first dorsal fin has a spike. Tail in the form of a tourniquet. Marine. The female lays 1-2 eggs with a filiform appendage.

6. Class Bony fish

General characteristics:

Bone scales develop in the skin. Skull hyostylic or amphistylic (loosely attached to cranial box). The tail is hetero-, homo-diphycercal. 5 pairs of gill slits covered by a common gill cover. A swim bladder is formed. Some have lungs (double breathing), some retain the arterial cone (cross-finned), others are replaced by the aortic bulb. Fertilization is external, in some internal - there is a capulative organ - an outgrowth of the anal fin. Neutral buoyancy - 2 types: open and closed bubble. 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 color change under the action of the central nervous system. Scales are protective bony formations in the skin. The crossopterans have cosmoid scales in the form of a bone plate, externally covered with cosmin. Ganoid scales, covered with ganoid, arose from the cosmoid. Ganoid scales can grow together with each other, forming a shell. Normal scales - cycloid - in the area of ​​the lateral line in the scales there are 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, gallbladder.

Respiratory system: 2 types of breathing: air and water. Aquatic: oxygen from water - gills. Air - from the air - the 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 crossopterygians, the reproductive and excretory systems are connected, the vas deferens flows into the kidney. The Wolfian canal is the function of the vas deferens and ureter, the Müller canal is the function of the oviduct. care for offspring.

CNS and sensory organs: The brain is divided into 5 sections: anterior (olfactory lobes). Intermediate brain. Midbrain (2 visual lobes). The cerebellum covers the medulla oblongata. Eyes.

SYSTEMATICS:

1. P / class. lobe-finned- scales cosmoid or bone. The notochord persists throughout life. The paired fins are covered with scales. Beaded fin. In the intestines there is a spiral valve, in the heart - an arterial cone. There is a cesspool.

1) N/neg. CrossopterygiansNeg. coelacanths

2) N/neg. Dipnoi Neg. Horn-toothed or one-lung,Neg. Bipulmonary

2. P / class. ray-finned- ganoid or bone scales. There are naked, with shells. Joan is not. The fins are formed by bone rays - lipidotrichia → name. The arterial cone is replaced by the aortic bulb. Instead of light swim bladder.

Cartilaginous ganoids

Neg. sturgeons Sem. Sturgeon Fam. paddlefish

Neg. Polyperiformes

Bone ganoids

Neg. Amieformes

Neg. shell-shaped

3. P / class. bony- bone scales. High degree of ossification. Bone rays supporting the leathery edge of the gill cover are developed. In the heart, instead of an 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, without bone rays - fatty.

1 ) N/neg. Clupeoid (herring)

Neg. herring Sem. Herring Sem. Anchovies

Neg. salmon

Neg. cetaceans

Neg. Myctophiformes

2) N/neg. Aravanoid

Neg. Aravaniformes

Neg. beaked

3 ) N/neg. Angveloid

Neg. eels

Neg. Saccular

Neg. Spinosiformes

4) N/neg. Cyprinoids

Neg. Cypriniformes

Neg. Catfish

7) N/neg. percoid

Neg. Sticklebacks

Neg. Cithale-shaped

Neg. Perciformes

Neg. Flatfishes

IN THE OREN. REGION: family of Karpovs (rudd, asp, tench, podust, gudgeon, bleak, crucian carp, carp). from the loach family from the catfish family from the perch family, zander, bersh, perch, from the cod burbot family.

7. Superclass Quadrupeds. Class Amphibians or Amphibians

Class 4 - Amphibians, reptiles, birds, mammals.

Amphibians - anamnia (primary aquatic): 1) the main development in the aquatic environment 3) there is a stage of metamorphosis 4) eggs develop without the formation of embryonic membranes

Origin and evolution. The transition of vertebrates from an aquatic to a terrestrial way of life is accompanied by the appearance of breathing atmospheric oxygen and movement on a solid substrate. In parallel, other organ systems also changed: integument, blood circulation, sensory organs, and the nervous system. The first amphibians that appeared in fresh water at the end of the Devonian are ichthyostegida. They were true transitional forms between lobe-finned fish and amphibians, they had the rudiments of a gill cover, a real fish tail. The skin was covered with small fish scales. However, along with this, they had paired five-fingered limbs of terrestrial vertebrates. Later, in the Carboniferous period, a number of branches arose ( labyrinthodonts). In the Carboniferous, a second branch of primary amphibians also arose - lepospondylus - stegocephalic(shell-headed) for a solid shell of skin bones that covered the cranium. The ancestors of stegocephals were bone fish. They are closest to stegocephals lobe-finned fish. Stegocephalians survived until the beginning of the Mesozoic. Modern detachments of amphibians are formed only at the end of the Mesozoic. intensive speciation of modern amphibians began in the early Mesozoic.

Amphibious class. Adults are characterized by paired limbs with a hinge joint, unequal. The skull is attached to 1 cervical vertebra, an atlas is formed - the occipital joint (the head is mobile). The upper element of the hyoid arch - pendants - turns into the auditory ossicle of the middle ear - the stirrup. The pelvic girdle is connected to the transverse processes of the sacral vertebrae. 2 circles of blood circulation are formed, but they are not completely separated. The lateral line organs disappear in adults. Signs of aquatic animals: 1) the 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 secret can be poisonous (toad, toad). The corium contains pigment cells. The cells of the epidermis become keratinized, claws and nails appear. The legless have bony scales scattered in the corium. Anurans under the skin have lymphatic lacunae - reservoirs that allow, under favorable conditions, to accumulate water supplies.

Muscular and digestive system: The muscles of the limbs increase, the oral cavity becomes more complicated. All adults are carnivorous; larvae can feed on algae and detritus. Prey is captured with the help of the tongue. There is a pancreas, a liver.

Respiratory system: 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 is 3-chambered. Blood mixes in the ventricle. Hollow veins appear, they are paired, formed by mixing 3 veins, mixed blood. The bone marrow appears for the first time.

Excretory organs, water-salt metabolism: Larvae have head buds (probuds). During metamorphosis, trunk buds appear. There is a bladder. Decay products: in larvae - ammonia, in adults - urea.

reproductive system: paired sex glands. The function of the oviduct is the Muller canal.

In males: testes → vas deferens → kidney, where they open into the Wolf canal, the lower part of which forms a swelling - the seminal vesicle (reservoir for storing reproductive products). In anurans, fertilization is external (in males, genital calluses are on the paws to hold the female). In caudates - internal. Neoteny - the ability of larvae to sexual reproduction (ambystoma, axolotl) (under unfavorable conditions)

CNS, sense organs: The 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. The organs of vision are developed in almost everyone. Developed color perception.

Systematics

P / Class Arcuvertebral

N/neg. Jumping

Neg. Primitive anurans

Neg. tailless- flattened body, small limbs, large head. Hind limbs powerful pushing.

Sem. round-language- Protective coloring. Midwife toad - the female lays eggs in the form of cords, the male fertilizes and carries on her paws until hatching.

Sem. pip- Surinamese pipa - the female lays eggs on her back, the male fertilizes and presses into the skin. Cells are formed around the eggs. They stay there until they become frogs.

Sem. spadewort

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 disks (suckers). Caring for offspring. Representatives: blacksmith tree frog (they build a pool where they lay eggs), marsupial tree frog - on the back of a bag where eggs are laid

Sem. real frogs- Goliath frog, brown, grassy, ​​green frogs

Sem. copepods

P/Class Thin Vertebrates

Neg. Tailed- the body is compressed from the sides, a small head, a tail-balancer, limbs on the sides, small, equal

Sem. Siren- descended from the neotenic larvae of the ambistome. There is no adult stage. There are only forelimbs, external gills are preserved throughout life, there are lungs

Sem. Proteic- 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 dry land. Representatives: common newt and comb

Sem. Lungless salamanders

Neg. legless- Representative: worms - a worm-like body, a small head. Constrictions divide the body into segments. Limbs and their belts are absent, there is no tail, at the end of the body there is a cloaca. They secrete poisonous mucus. Underground lifestyle, some aquatic. Viviparous.

8. Class Reptiles or Reptiles

Amniotic signs:

1) Embryonic development in the air with the formation of embryonic membranes (serous, amnion, allantois)

2) The eggs are large, covered with a shell

3) Internal fertilization

4) Strengthening care for offspring

5) No larval stage

Origin of reptiles: Terrestrial vertebrates arose in the Devonian. These were armored amphibians, or stegocephalians. They were closely associated with water bodies, since they bred only in water, lived near water bodies, where there was terrestrial vegetation. Rearrangements: adaptations for protecting the body from drying out, for breathing atmospheric oxygen, walking on a solid substrate. All these features took shape in reptiles. Mesozoic reptiles are primarily terrestrial animals. Many of them have adapted to life in the water. Some mastered the air environment. The oldest reptiles are known from the upper Permian deposits of North America, Western Europe, Russia, and China. They are called cotilosaurs. Most of the groups have acquired greater mobility; their skeleton became lighter, but at the same time stronger. The solid shell of the skull has undergone a partial reduction. The present-day crypto-necked and side-necked tortoises to a greater extent preserve the primary appearance of the Triassic land tortoises. Marine and soft-skinned 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. Crocodiles of the modern type are descended from ancient archosaurs - pseudosuchians. They are known from the chalk. By the end of the Mesozoic, highly organized birds and mammals were increasingly developed.

Covers. 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 multilayer epidermis. The upper one is the stratum corneum, the lower one is the Malpighian layer (living, germ). Skin ossifications (plates) lie in the skin. The skin has lost the ability to permeate water and gases. Under the epidermis there is a corium, in the upper layer of which there are pigment cells (coloration).

Skeleton. In the axial skeleton: cervical, thoracic, lumbar, sacral, caudal. In the cervical, the first 2 vertebrae are differentiated (atlas with epistrophy). The lumbar region has short ribs. Capable of autotomy (tail drop).

Circulatory system. An incomplete septum appears in the heart. Mixed blood with a predominance of arterial.

Digestive system: Mostly predators. In the oral cavity there are glands without enzymes. Poisonous ones are converted into poisonous ones. There is a liver, pancreas.

Excretory organs: The kidneys are metanephric, located in the pelvic cavity. 2 types of filtration:

1. those that live in water - a well-developed filtering apparatus (glameruli and nephron). Allocate products into the lumen by filtering the blood plasma. 2. in land animals - the secretory apparatus of the renal tubules is enhanced. The end product of metabolism is uric acid.

reproductive system: Dioecious.

CNS and sensory organs: The brain is enlarged. The olfactory lobes are developed, there is a pituitary gland and an epiphysis. The cerebellum is enlarged. There are 11 pairs of cranial nerves. The organs of hearing are the middle (the stirrup is in it) and the inner ear.

Systematics

1) P / cl. Anapsida (neg. Turtles)

2) P / class. Archosaurs (neg. Crocodiles)

3) P / class. Lepidosaurs (neg. Beakheads, neg. Scaled)

1) P / class Anapsida

Neg. Turtles- Modern ones have a shell consisting of a dorsal shield - a carapace and an abdominal one - a plastron. The carapace is formed by bone plates of skin origin. The ribs and trunk spine are fused with it. The plastron is formed from bone plates. From above, the shell is covered with horny shields. Only the caudal and cervical regions are movable; the rest is fused with the carapace. Jaws without teeth. Well developed lungs. Additional respiratory organs are paired anal bladders and outgrowths of the pharynx. Well developed vision, sense of smell. 5 suborders: P/neg. Hidden neck turtles Sem. freshwater,Sem. Land;P/neg. sea ​​turtles; P/neg. Soft-shelled turtles (soft-skinned); P/neg. Side-necked turtles; P/neg. Turtles

2) P / class. Lepidosaurs

Neg. beakheads- 1 view. Tuatara or Hatteria is the oldest species among modern ones. Up to 70 cm. Island of New Zealand. Protected.

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- sea, wood, land .; Sem. Agamas; Sem. real lizards- viviparous.; Sem. Fusiform; Sem. monitor lizards- the largest, arboreal, terrestrial; Sem. Yadozuby- 2 types. Poisonous; earless monitor lizards.

P/neg. Amphisbaena (two-walkers)

P/neg. snakes- Legless. They are able to open their mouth wide - a movable articulation of the bones of the facial part of the skull. Poisonous ones have poisonous glands and teeth. Belts and limbs are absent. Sem. Slepuns- digging lifestyle; Sem. false-footed; Sem. already shaped;Sem. aspids are mostly poisonous. Sem. sea ​​snakes. Sem. Vipers Sem. pitheads.

P / class Archosaurs

Neg. crocodiles

The body is valky, 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. Live up to 180 years. Sem. alligators, Sem. real crocodiles, Sem. gharials– 1 species – Gavialus Ganveticus (Indostan)

9. Bird Class

Origin of birds. P their rarest were ancient lizard reptiles - archosaurs. By the beginning of the Mesozoic (Triassic) - birds. 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 specialized for climbing by grasping the branches with their fingers. Subsequently, the ability to jump from branch to branch developed. Scales, forelimbs formed 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 insulation role, and determined the homoiothermy of birds. The immediate ancestors of birds have not yet been established. In the last century, in the Jurassic deposits were found and described archeopteryx. There are currently seven known fossil remains of Archeopteryx. Archeopteryxes are 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 skin layer is divided into the skin itself - the dermis, blood vessels pass through it, the feathers are strengthened, and muscle fibers are located. The second layer - subcutaneous tissue - a loose layer adjacent to the muscles, accumulates fat reserves. One gland - coccygeal (well developed in waterfowl) - produces a fat-like secret. They lubricate the feather, prevent wetting, a source of vitamin D. The growth of the keratinized layer of the skin forms the horny cover of the beak - ramphoteka. Horny scales cover the fingers, prehensile, part of the lower leg. In some species, males form a bone outgrowth on the flail - a spur.

Pen types, structure: The main feather is contour, consists of a rod, 2 fans on the sides. The part of the trunk to which the fan is attached is called the stem. The lower part is the chin, fixed 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. Hooks fastening with each other, form a plate of the fan. Pigments accumulate in feathers - melanins (black, brown color) and lipochromes (red, yellow, green). Contour feathers are fixed in the skin in special fields - pterylia, they alternate with fields where there are no quills of the feather - apterylia. Under the contour feathers - downy (thin rod, beards without hooks).

Propulsion system: The peculiarity of the structure of the neck muscles allows you to turn your head 180 0, owls 270 0. The thoracic vertebrae fuse into the dorsal bone, connect to the sacrum, the trunk is immobile. There is a large sternum with a process - a keel, for attaching the muscles involved in the flight. The tail vertebra turns into a coccygeal bone - a pigastil, the bases of the tail feathers are attached to it. The jaw turns into a beak. The clavicles fuse into a fork - the role of a shock absorber during a wing stroke.

Digestion: In filterers - the tongue is fleshy, in those who feed on nectar - it folds into a tube, in woodpeckers - with hooks. Salivary glands (some have amylase). Some have a goiter - an expansion of the lower part of the esophagus (temporary storage of food when the stomach is full; in pigeons, the cells of the goiter undergo fatty degeneration - bird's milk).

Breath: Through the nostrils, air enters the nasal cavity → choanae → oral cavity. There are 2 larynxes - the upper one (does not have vocal cords), behind which is the trachea, and the lower one (forms the vocal apparatus). Sounds are generated by vibrations as air passes through the eardrums.

Inhalation-exhalation is carried out due to the movement of the chest. Oxygen saturation occurs continuously during inhalation and exhalation (double breathing).

Isolation, water-salt exchange: kidneys → ureters → cloaca. The metabolic product is uric acid. A loop-like section appears in the nephron - the loop of Henle (water readsorption) - allows you to remove harmful substances.

reproductive system: In females: only 1 left ovary develops. Fertilization in the upper part of the oviduct. Holases (cords) - the dense part in the egg - allows 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, sense organs: 12 pairs of cranial nerves. The main receptor is vision. Color vision. Recognize sweet, bitter, salty. Thermoreceptors, touch receptors.

Systematics:

Aquatic, near-water birds

N/neg. floating

Neg. penguins Neg. loons Neg. Toadstools.Neg. Petrel-like (Tube-nosed) Neg. Pelicans (Copepods) Neg. Storks (Archives) Sem. Herons, Storks, Ibises, Flamingos . Neg. Anseriformes

Birds of open landscapes

Neg. ostriches Neg. Nandu-shaped Neg. cassowaries Neg. Kiviformes (Wingless) Neg. Falconiformes P/neg. Amer. Vultures P/neg. falconsSem. Hawks, Falcons. Neg. Galliformes Neg. Cranes Sem. Real Cranes, Bustards Neg. Pigeons Neg. parrots Neg. cuckoo 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. Hornbeaks P/neg. Screaming P/neg. passerines Sem. Larks Sem. swallowtail Sem. crows Sem. Blue fam. Thrush Sem. Wagtail Sem. Starlings Sem. finches

10. Class Mammals or Animals

The progressive evolution of mammals has been associated with the acquisition of: high body temperature, the ability to thermoregulate, 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 led to the immiscibility of arterial and venous blood, in the appearance of a secondary bone palate, which provided breathing during meals, accelerated digestion of food. changes in the structure of the jaws, differentiation of teeth, development of the jaw muscles. The animal-toothed reptiles closest to mammals were cynodonts. The most pronounced features of skeletal changes were found among them in thrinaxodon from the early Triassic. In the subsequent development of mammals, paleontologists emphasize changes in the dental system. This led to the separation of two groups - morganucodonthod and Cuneotheriidae→Eupantotherium. Biologically, they were to a certain extent close to terrestrial and arboreal insectivores. At the end of the Mesozoic, the division into two independent stems - Inferior, marsupials, and higher, placental. The oldest group of marsupials is the opossum family.

Placental mammals arose in the Cretaceous period. Fossil monkeys have been known since the Paleocene. tree monkeys - propliopithecus- gave rise to gibbons and close to anthropoids, Ramapithecus. Of great interest are 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) First passers (first beasts)

2) Real mammals (animals)

There are egg-laying mammals.

Covers: 1) Epidermis (multilayer, keratinized) → dermis → fiber. The epidermis is the lower layer of cells, they become keratinized and rejected (dandruff). Derivatives of the epidermis - hair, nails, etc. in the epidermis there is a pigment - melanin (coloring, tanning, protection from sunlight). 2) Corium (skin itself) - formed by fibrous tissue, rich in blood vessels. The lower layer of the corium is subcutaneous fat.

2 types of hair: outer (long, hard) and down (soft). The outer hair consists of a trunk protruding outward and the base of the bulb, reinforced in the dermis. Glands (derivatives of the epidermis): sebaceous - their ducts open into the hair bag. The secret lubricates the skin, 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 in the blood gap.

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 (do not connect). The skull has a zygomatic arch. Limb belt - scapula, clavicle. Free department - shoulder, forearm, hand. Belt of the 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 (raznozubnost) - incisors, canines, small and large molars. Salivary glands - enzymes (amylase), a bactericidal substance (lysozyme), stomach - single-chamber (carnivores) and multi-chamber (herbivores), consists of departments - scar, mesh, book, abomasum.

Respiratory system: Breathing due to the movement of the chest. Oral or nasal cavity → larynx → trachea → lungs (ending with alveoli). 2 types of breathing - abdominal (predominant in herbivores) and chest (predominant in carnivores).

Circulatory system: 4-chambered heart, 2 atria, 2 ventricles.

Excretory organs: The kidneys are pelvic, metanephric (in the pelvic cavity). Consist of 2 layers - cortex and medulla. The unit of the kidney is the nephron. Metabolic products - urea.

reproductive system: In males: the testicles are placed in the scrotum. Around the testicles is the appendage of the testis (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), bifid. The cervix opens into the vagina. The ovaries mature in the follicle - Graf's vesicle. The egg enters the abdominal genital funnel. Fertilization occurs in the upper part of the oviduct.

Systematics

P / class Cloacae (first beasts) - The most primitive. They lay eggs and incubate them. Neg. single passSem. Yachidna- the body is covered with needles, have a beak. Sem. Platypuses- semi-aquatic, between the fingers of the membrane. They filter the water.

P/class Animals

N/neg. marsupials

Neg. marsupials- Babies are born prematurely, carried out in a pouch. There are mammary glands in the bag. Sem. opossums, Sem. carnivorous marsupials, Sem. Marsupial badgers (bandicoots), Fam. Couscous- herbivores, Sem. Kangaroo

N/neg. Higher Beasts (Placental)- capable of sucking milk

Neg. Insectivores Sem. Hedgehogs- in Orenb. Region - eared and ordinary hedgehogs, omnivores, Sem. Moles, Sem. shrews- the smallest - a tiny baby shrew (2-3 g)

Neg. Woolly wings (kaguans) Neg. Bats– echolocation, active at night

P/neg. fruit bats

P/neg. The bats They feed on blood, nectar, insects Sem. bagwings, Sem. fish-eating, Sem. False vampires, Sem. Vampires, Sem. common bats

Neg. edentulous- characterized by underdevelopment of teeth. Sem. Anteaters,Sem. armadillos

Neg. Lagomorphs Sem. pikas, Sem. Hares

Neg. rodents Sem. beaver, Sem. squirrels, Sem. jerboas, Sem. Mouse, Sem. Hamsters, Sem. Agouti, Sem. Chinchilla

Neg. cetaceans- forelimbs - flippers, hind limbs are absent.

P/neg. baleen whales Sem. Smooth (real) whales, Sem. Gray whales, Sem. Stripes

P/neg. toothed whales-there are teeth (homogeneous). Sem. river dolphins, Sem. Sperm Whales, Sem. Dolphins

Neg. PredatorySem. Doggystyle, Sem. Raccoons, Sem. Bears, Sem. Cats, Sem. Hyenas

Neg. pinnipeds Sem. eared seals, Sem. real seals, Sem. walruses

Neg. Odd-toed ungulates- the phalanges of the fingers end in a hoof. Sem. Tapirs, Sem. Rhinos

Neg. artiodactyls- an even number of fingers

P/neg. Non-ruminants- simple stomach, 4-fingered limbs 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. calluses- limbs have 2 fingers, devoid of hooves Sem. camels

Neg. Primates- 5-toed, plantigrade. 1 finger is opposed to the rest. Odd-toothed. Big brain, convolutions appear

P/neg. Lower primates (semi-monkeys)Sem. Tupai- primitive, woody Sem. Lemurs, Sem. Lori– arboreal, tropics

P/neg. Greater primates (monkeys) Section of broad-nosed monkeys: small marmosets, callimico and major capuchin monkey. Narrow-nosed section: Sem. Monkeys,Sem. Gibbon, Sem. hominids

Type Chordates combines animals that are different in appearance, living conditions, lifestyle. Representatives of this type are found in all the main environments of life: in water, on land, in the thickness of 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 non-cranial, cyclostomes, fish, reptiles, amphibians, mammals, and birds. Tunics can also be attributed to this type - this is a peculiar group of organisms that lives on the bottom of the ocean and leads an attached lifestyle. Sometimes included in the phylum Chordates are enteropneas, which have some of the characteristics of this type.

Characters of the chordate type

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 chord or dorsal string. The notochord is a special non-segmented and elastic cord that embryonic develops from the dorsal wall of the embryonic intestine. The origin of the notochord is endothermal.

Further, this cord can develop in different ways, depending on the organism. For life it remains only in the lower chordates. In most higher animals, the notochord is reduced, and the vertebral column is formed in its place. That is, in higher organisms, the notochord is an embryonic organ that is displaced by the vertebrae.

Above the axial skeleton is the central nervous system, which is represented by a hollow tube. The cavity of this tube is called the neurocoel. Almost all chordates are characterized by a tubular structure of the central nervous system.

In most organisms of the chordate type, the anterior section of the tube grows to form the brain.

The pharyngeal section (anterior) of the digestive tube comes out with two opposite ends. The outgoing openings are called visceral fissures. Lower type organisms have gills on them.

In addition to the above three 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. Chordates also have bilateral body symmetry.

The phylum Chordates is divided into subtypes:

• Skullless;
• tunicates;
• Vertebrates.

Subtype Cranial

This subtype includes only one class - the Head Chordidae, and one order - the Lancelets.

The main difference of this subtype is that these are the most primitive organisms, and all of them are exclusively marine animals. They are distributed in the warm waters of the oceans and seas of temperate and subtropical latitudes. Lancelets and epigonichites live in shallow water, mainly burying themselves with the back of the 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, since all the signs of chordate organisms are preserved in it for life, which makes it possible to understand the principles of the formation of chordates and vertebrates.

Subtype Shellers

The subtype includes 3 classes:

• salps;
• ascidians;
• Appendiculars.

All animals of the subtype are exclusively marine.

The main difference between these chordates is that in almost all organisms in the adult state there is no chord and neural tube. In the larval state, all type traits in tunicates are pronounced.

Tunicates live in colonies or singly, attached to the bottom. There are much 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 rounded 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, they can reproduce both sexually and asexually.

It is known that the ancestors of these organisms were free-swimming, while at the present time only tunicate larvae can move freely in the water column.

Subtype Vertebrates

Skull animals are the highest subtype. 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, a mate 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 the cranial is more differentiated than that of the lower animals of the same type. Vertebrates have a well-developed brain, which contributes to the functioning of higher nervous activity. It is the higher nervous activity that is the basis of adaptive behavior. These animals have well-developed sense organs, which are necessary for communication with the environment.

As a result of the emergence of the sense organs and the brain, such a protective organ as the skull has developed. And instead of a chord, this subtype of animals has a vertebral column, which performs the function of supporting the entire body and a case for the spinal cord.

All animals of the subtype develop a mobile jaw apparatus and oral fissure, which develop from the anterior intestinal tube.

The metabolism of this subtype is much more complicated than that of all the animals discussed above. Cranials have a heart that provides fast blood flow. The kidneys are essential for removing waste products from the body.

The subtype Vertebrates appeared only in the Ordovician-Silurian, but in the Jurassic, all currently known types and classes already existed.

The total number of modern species is slightly more than 40 thousand.

Vertebrate classification

Very diverse type of chordates. The classes that exist 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 organisms.
• Terrestrial organisms.

Primary aquatic organisms

Primary aquatic differ in that they either have gills throughout their 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 Jawless

• Class Cyclostomes.

These are the most primitive cranial animals. They actively developed in the Silurian and Devonian; at present, their species diversity is not high.

Section Jaws

Superclass Pisces:

• Class Bony fish.
• Class Cartilaginous fish.

Superclass Quadrupeds:

• Class Amphibians.

These are the first animals in which the jaw apparatus appears. This includes all known 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 embryonic membranes are formed in animals during the development of the egg. If the species lays its eggs on the ground, then the embryonic membranes protect the embryo from external influences.

All chordates of this group live mainly on land, have internal fertilization, which indicates 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 says that this type of organisms originated from the larvae of the enteropretis. Most representatives of this class lead an attached lifestyle, but their larvae are mobile. Considering the structure of the larvae, one can see the beginnings of the notochord, the neural tube and other features of the chordates.

Another theory is that the Chordata phylum is descended from the crawling, worm-like ancestors of the intestinal-breathers. They had the beginnings 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 catching food from the water column.

The article considered 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.

More than 40 thousand modern species of animals are classified as chordates. These animals are very diverse in external structure, lifestyle and living conditions.

General features of the structure of chordates:

• The presence of an internal axial skeleton, the basis of which is a dense, elastic and elastic dorsal cord - chord. It occurs in all chordates in the early stages of development of their embryos(in lower chordates, it persists throughout life, in higher ones it exists only in embryos, in adults it is replaced by a spine).
• The nervous system looks like tubes located on the dorsal side - over the chord ( formed from a layer ectoderm). In higher chordates anterior neural tube grows and forms the brain.
• All chordates - bilaterally symmetrical animals. Runs along their body digestive tube- Intestine that starts at the mouth and ends at the anus.
• All chordates in embryonic development have gill slits - paired transverse openings penetrating the anterior part of the digestive tube.
• Circulatory system chordates closed. Heart located on the ventral side of the body under the alimentary canal.

The phylum Chordates includes three subtypes: Non-cranial, Tunicates, and Vertebrates (Cranial).

Subtype Cranial It is represented by a small group of marine chordates and includes one class - Lancelet, which includes about 30 species of small animals. The name "skullless" suggests that representatives of this subtype do not have a skull or brain. The structure of the non-cranial is quite primitive:

• The notochord serves as their internal skeleton throughout their lives.
• The functions of the central nervous system are performed by the neural tube.

Subtype Shellers (Larval chordates, or Tunicates), includes about 1500 species of marine chordates. The tunicates the main features of the Chordata type are clearly expressed only at the larval age.

At the initial stage of life, tunicates are free-swimming larvae that move with the help of a tail. The larvae of the tunicates have a complex structure similar to that of the lancelet. As the larva develops into an adult, its structure is simplified. In adulthood, most of them lack the notochord and neural tube. The body of an adult tunic is enclosed in a gelatinous shell - a tunic - and resembles a bag with two funnels through which water enters and exits. With water, the animal receives oxygen for breathing and food - organic particles. The tunicates are hermaphrodites. Many species reproduce by budding, forming colonies.

Subtype Vertebrates unites most species of chordates. For this subtype Classes include: Cartilaginous fishes and Bony fishes, Amphibians, Reptiles, Birds and Mammals. In terms of structure and lifestyle, vertebrates are at a higher level of organization than non-cranial and tunicates.

In contrast to the sedentary and passively feeding non-cranial ancestors of vertebrates, they switched to an active search for food and the movement associated with it. This led to the development of a powerful internal skeleton and muscles, the improvement of the processes of respiration, nutrition, blood circulation, excretion, sensory organs and the central nervous system.

The Chordata phylum is one of the largest in terms of the number of species in the animal kingdom. In total, it contains about 42 thousand modern species. Chordates appeared at the beginning of the Paleozoic, more than 500 million years ago. It is believed that they originated from some ancient annelids. Representatives of this type have common features and a single structure plan.

The internal axial skeleton is the chord - an elastic, dense and elastic cord. With the development of the embryo, the notochord is formed from the endoderm layer, separating from the dorsal part of the embryonic gut. In lower chordates, it plays the role of an internal axial skeleton for life, in higher animals it functions as an axial skeleton only in embryonic development, and in adult animals it is replaced by a spine.

The central nervous system, where the nerve centers (clusters of neuron bodies) are located, in chordates is represented by the neural tube, which, during the development of the embryo, is formed from the ectoderm layer. The neural tube is located above the chord. In lower chordates, it is not divided into sections, while in higher ones it is divided into the spinal cord and brain.

The anterior part of the digestive tube is the pharynx. It has gill openings and functions as a common division of the digestive and respiratory systems. In lower chordates, gills develop on the interbranchial septa, which function throughout life. In higher chordates, gill rudiments appear at certain stages of embryonic development, and lungs develop in adult animals.

In addition to these main features, chordates have other characteristic features. Chordates are deuterostome, secondary cavity, bilaterally symmetrical animals. The secondary mouth occurs in them at the early stages of embryonic development, when an anus is formed in place of the primary mouth, and a mouth is formed at the opposite end of the body (from invertebrates to deuterostomes are echinoderms). In chordates, striated muscles develop, and the head section with sensory organs separates. The circulatory system is closed; higher chordates develop a muscular pumping organ - the heart.

Such a structure of chordates turned out to be evolutionarily progressive. This allowed them to master all habitats, spread throughout the globe. Chordates are very diverse (Fig. 111) and are represented by various ecological groups, an abundance of species, many of which reach a high abundance.

The chordate type is divided into three subtypes. Two of them - Cranial and Cranial, or Vertebrates, are considered in this course of zoology. The non-cranial subtype includes one class - Lancelets, the cranial or vertebrate subtype includes: Fish, Amphibians, Reptiles, Birds and Mammals.

Subtype Cranial (Acrania)

Skullless- marine, mainly bottom animals, retaining characteristics of the chordate type for life. These are the most primitive chordates, so their study is important for understanding the origin of chordates and the initial stages of their evolution.

The lancelet is a primitive chordate

Class Representatives lancelets live in shallow waters, in the coastal part of warm seas and oceans. In our country lancelets found in the shallows of the Black and Japan Seas. Only about 30 modern species are known.

In terms of external structure, the lancelet resembles a small translucent fish 4-8 cm long. It stretches along the body from the upper side dorsal. He goes into tail , which is similar in shape to a medical instrument lancet. For this similarity, the lancelet got its name. It was first described by the Russian academician P.S. Pallas in 1774. The lancelet does not have paired fins. The skin is very thin, through them translucent internal organs.

The lancelet retains all the signs of chordates for life.

Its internal axial skeleton is represented by a chord stretching along the body. The notochord and the neural tube lying above it are surrounded by a connective tissue sheath. The central nervous system is the neural tube. Numerous sensory and motor nerves depart from it, forming the peripheral nervous system. In the skin there are tactile cells, in the neural tube, among other nerve cells, light-sensitive eyes.

Under the notochord is the digestive tube. Its anterior part - the pharynx - has gill openings. Therefore, the pharyngeal intestine performs the functions of both the digestive and respiratory systems. Gill arteries (thin blood vessels, capillaries) pass through the interbranchial septa, through which oxygen enters the blood, and carbon dioxide is released into the water. Gas exchange occurs due to the difference in pressure between gases.

At the bottom of the pharynx is a groove lined with ciliated cells. The movements of the cilia create a stream of water that washes over the gills. Small food particles that have fallen into the pharynx stick together and are sent by a stream of water into the digestive tube. Under the influence of digestive juices, food is digested, and undigested residues are removed through the anus.

The circulatory system is closed. Through a large abdominal vessel, blood moves forward to the gills, where it is oxidized (enriched with oxygen). Through the dorsal vessel (spinal aorta), this arterial blood is carried to all organs of the body. The lancelet has no heart. Blood moves by contraction of the so-called "gill hearts" - the walls of the abdominal vessel at the base of the gill arteries.

The excretory organs of the lancelet are similar to the excretory organs of annelids and are excretory tubes that open into the body cavity at one end, and flow into the common canal at the other. Several common excretory canals open outwards.

Most of the time lancelets spend burrowing into the sand and exposing the front end of the body with a preoral funnel surrounded by tentacles. The lancelet feeds on protozoa and unicellular algae. The anterior end of its body is surrounded by a fold of skin that forms the peribranchial cavity. This protects the gill slits from solid particles entering them.

Lancelets, like most other chordates, are dioecious animals. In females, eggs are produced in the ovaries; in males, spermatozoa are produced in the testes. Fertilization is external: the penetration of spermatozoa into the eggs occurs in water. Lancelets breed in the warm season, from spring to autumn.

The lancelet is one of the most primitive representatives of the chordates and retains all of their main features throughout their lives. The notochord serves as its axial skeleton, the neural tube serves as the central nervous system, the pharynx has gill openings, and there is no heart in the circulatory system. The lancelet is a dioecious animal that is characterized by external fertilization.

Subtype Cranial, or Vertebrate (Vertebrata)

General features of the subtype

The subtype Cranial, or Vertebrates, includes most of the chordates: the classes Cartilaginous and Bony Fish, Amphibians, Reptiles, Birds and Mammals.

Vertebrates are distinguished by a higher level of development than non-cranial ones. Their body is supported by the spine, which in adult animals replaces the notochord. The central nervous system is especially improved: the neural tube is divided into the brain and spinal cord. The sense organs are well developed. The skull develops to protect the brain. Paired limbs are formed: in fish - paired fins, in terrestrial vertebrates - five-fingered limbs. Unlike non-cranial vertebrates, a muscular heart appears in the circulatory system. The excretory organs are the kidneys. Vertebrates lead an active lifestyle, sometimes making distant migrations. They are distributed throughout the globe, have mastered all habitats. Many modern vertebrate species reach high numbers.