Block 3. System, diversity and evolution of living nature

Kingdom Animals

TYPE CHORDS. SUPERCLASS FISH

Fish are the largest group of vertebrates. Fish are classified into the class Cartilaginous fishes (sharks, rays ) and class Bony fishes (sturgeon, salmon, herring, crucian carp, pike, swordfish and etc.). The main criterion for such a division is the substance that makes up the internal skeleton of fish:cartilage or bone.

Animals of this, the most prosperous group of vertebrates today, can be found in all corners of our planet - from North Pole to the South. They are also found in brackish waters seas and oceans, and in fresh waters of lakes and rivers; live in the dark depths of ocean trenches, and in sun-drenched coral reefs. The number of their forms is innumerable, and each fish is in amazing harmony with its environment.

Fish are a large group of vertebrates. The branch of zoology that studies fish is calledichthyology .

General characteristics of fish

Fish are vertebrates that live in water (in an environment much denser than air). The body of a fish is remarkably adapted to the implementation of all vital functions in the water. The body of the fish is usually covered with scales and has a streamlined shape. It consists of three parts:heads, torsos And tail . The main respiratory organ is the gills. Like other vertebrates, fish have a hard skeleton, musculature, skin covering, digestive, circulatory and nervous systems, respiratory, excretion and reproduction.

Fish are cold-blooded animals: their body temperature is close to environment. Therefore, we can say that the rate of metabolic processes depends on the temperature of the water.

Today, about 25 thousand species of fish are known.

Habitat and external structure of fish

The habitat of fish is various water bodies of our planet: oceans, seas, rivers, lakes, ponds. It is very extensive: the area occupied by the oceans exceeds 70% of the Earth's surface, and the deepest depressions go 11 thousand meters deep into the oceans.

The variety of living conditions in the water influenced the appearance of fish and contributed to a wide variety of body shapes: the emergence of many adaptations to living conditions, both in structure and in biological features.

General plan of the external structure of fish

On the head of the fish are eyes, nostrils, mouth with lips, gill covers. The head smoothly merges into the body. The trunk continues from the gill covers to the anal fin. The body of the fish ends with a tail.

Outside, the body is covered with skin. Protects the skin of most slimy fishscales .

The locomotion organs of fish arefins . The fins are outgrowths of the skin that rest on the bones.fin rays . The tail fin is the most important. From the bottom on the sides of the body are paired fins: pectoral and ventral. They correspond to the fore and hind limbs of terrestrial vertebrates. The position of the paired fins different fish varies. The dorsal fin is located on top of the body of the fish, and the anal fin is located below, closer to the tail. The number of dorsal and anal fins may vary.

On the sides of the body of most fish is a kind of organ that perceives the flow of water. Thislateral line . Thanks to the lateral line, even a blinded fish does not run into obstacles and is able to catch moving prey. The visible part of the lateral line is formed by scales with holes. Through them, water penetrates into a channel stretching along the body, to which the endings fit. nerve cells. The lateral line may be intermittent, continuous or completely absent.

Fin functions

Thanks to the fins, the fish is able to move and maintain balance in the aquatic environment. Deprived of fins, it turns over with its belly up, since the center of gravity is placed in the dorsal part.

unpaired fins (dorsal and anal) provide body stability. The caudal fin in the vast majority of fish performs the function of a mover.

Paired fins (thoracic and abdominal) serve as stabilizers, i.e. provide an equilibrium position of the body when it is immobile. With their help, the fish maintains the body in the desired position. When moving, they serve as bearing planes, a steering wheel. The pectoral fins move the fish's body when swimming slowly. The pelvic fins perform mainly the function of balance.

body shape

Fish have a streamlined body shape. It reflects the characteristics of the environment and lifestyle. In fish adapted to fast long swimming in the water column (tuna (2), mackerel, herring, cod, salmon ), "torpedo-shaped" body shape. In predators practicing fast throws at a short distance (pike, taimen, barracuda, garfish (1), saury ), it is "arrow-shaped". Some fish adapted to long stay at the bottom (stingray (6) , flounder (3) ) have a flat body. At certain types the body is bizarre. For example,sea ​​Horse resembles the corresponding chess piece: its head is at right angles to the axis of the body.

body integuments

Outside, the skin of fish is covered with scales - thin translucent plates. Scales with their ends overlap each other, arranged in a tile-like manner. This provides

strong protection of the body and at the same time does not create obstacles to movement. Scales are formed by special skin cells. The size of the scales is different: from microscopic toacne up to several centimetersIndian barbel . There is a wide variety of scales: in shape, strength, composition, quantity and some other characteristics.

Lie in the skin pigment cells - chromatophores : when they expand, the pigment grains spread over a larger area and the color of the body becomes bright. If the chromatophores contract, pigment grains accumulate in the center, leaving most of the cell uncolored, and the color of the body turns pale. If the pigment grains of all colors are evenly distributed inside the chromatophores, the fish has a bright color; if the pigment grains are collected in the centers of the cells, the fish becomes almost colorless, transparent; if only yellow pigment grains are distributed over their chromatophores, the fish changes color to light yellow.

Chromatophores determine the diversity of fish coloration, especially bright in the tropics. Thus, the skin of fish performs the function of external protection. It protects the body from mechanical damage, facilitates sliding, determines the color of the fish, communicates with external environment. The skin contains organs that sense temperature and chemical composition water.

Peculiarities internal structure and life of fish

Musculoskeletal system fish consists of a skeleton and muscles. The basis of the skeleton is formed by the skull and spine.Spine consists of individual vertebrae. Each vertebra has a thickened part - the vertebral body, as well as the upper and lower arches. The superior arches together form a canal in which the spinal cord lies. The arches protect him from injury. Up from the arcs stick out longspinous processes . The lower arcs in the trunk part are open. Adjacent to the lateral processes of the vertebraeribs - they cover internal organs and serve as a support for the trunkmuscles . Especially powerful muscles are located in fish in the back and tail. In the caudal part, the lower arches of the vertebrae form a canal through which blood vessels pass.

The skeleton also includes bones and bone rays.paired And unpaired fins . The skeleton of unpaired fins consists of many elongated bones, reinforced in the thickness of the muscles. Paired fins have skeletonsbelts and skeletons free limbs . The skeleton of the pectoral girdle is motionlessly attached to the skeleton of the head. The skeleton of the free limb (the fin itself) includes many small and elongated bones. In the abdominal girdle - a single bone. The skeleton of the free ventral fin consists of many long bones.

In the skeleton of the head, a smallscull, or cranium . The bones of the skull protect the brain. The main part of the skeleton of the head is made up of the upper and lower jaws, the bones of the eye sockets and the gill apparatus. In the gill apparatus, largegill covers . If you lift them up, you can seegill arches - they are paired: left and right. On the gill arches are the gills. There are few muscles in the head part, they are mainly located in the area of ​​the gill covers, jaws and on the back of the head.

Muscles are attached to the bones of the skeleton, which provide movement by their work. The main muscles are located evenly in the dorsal part of the body of the fish; the muscles that move the tail are especially well developed.

The musculoskeletal system performs various functions in the body. It serves as a support, allows you to move, protects from shocks and collisions. The skeleton protects the internal organs. Bony fin rays are a weapon of defense against predators and rivals.

Digestive system begins with a large mouth located at the end of the head and armed with jaws. There is an extensive oral cavity. There are small or largeteeth . Behind the oral cavity is the pharyngeal cavity. It shows gill slits separated by intergill septa. They have gills. They are covered with gill covers from the outside. This is followed by the esophagus and the voluminous stomach. Behind the stomach is the intestine. In the stomach and intestines, food is digested under the action of digestive juices: gastric juice acts in the stomach, in the intestines - juices secreted by the glands of the intestinal walls and pancreas, as well as bile coming from the gallbladder and liver. In the intestines, digested food and water are absorbed into the blood. Undigested residues are thrown out through the anus.

The digestive system provides the fish with essential nutrients.

The swim bladder is a special organ found only in bony fish. It is located in the body cavity under the spine. During embryonic development, it appears as a dorsal outgrowth of the intestinal tube. In order to fill the bubble with air, a newborn fry floats to the surface of the water and swallows air into the esophagus. Later, the connection of the swim bladder with the esophagus is interrupted.

Interestingly, with the help of the swim bladder, some fish are able to amplify the sounds they make. In some fish species, this organ is absent (for example, those living on the bottom or those that are characterized by rapid vertical movements).

The swim bladder prevents the fish from drowning under its own weight. It consists of one or two chambers, filled with a mixture of gases close in composition to air. The volume of gases in the swim bladder can change when they are released and absorbed through the blood vessels of the bladder walls or when air is swallowed. This changes the volume of the fish's body and its specific gravity. Thanks to the swim bladder, the body weight of the fish comes into balance with the buoyant force acting on the fish at a certain depth.

Respiratory system located in the pharynx.

The skeletal support of the gill apparatus is provided by four pairs of vertical gill arches, to which the gill plates are attached. They are made up of fringedgill filaments , inside which pass thin-walled blood vessels branching into capillaries. Gas exchange occurs through the walls of the capillaries: the absorption of oxygen from water and the release of carbon dioxide. Water moves between the gill filaments due to the contraction of the muscles of the pharynx and the movement of the gill covers. There are gill rakers on the gill arches. They protect soft tender gills from clogging with food particles.

Circulatory system fish is schematically a vicious circle consisting of vessels. Its main organ is the heart. Ittwo-chamber: comprises atrium And ventricle . The work of the heart ensures blood circulation. Moving through the vessels, the blood carries out gas exchange, the transfer of nutrients and other substances in the body.

The circulatory system of fish includesone circle of blood circulation . From the heart, blood flows to the gills, where it is enriched with oxygen. Oxygenated blood is calledarterial . It spreads throughout the body, gives oxygen to the cells, is saturated with carbon dioxide, that is, it becomesvenous and returns to the heart. In all vertebrates, the vessels that depart from the heart arearteries . The vessels that lead to the heart areveins .

excretory organs filter from the blood and remove water from the body and final products metabolism. The excretory organs are presented in pairs.kidneys along the spine,and ureters . Some fish have bladder.

Extraction from the branched blood vessels of excess fluid, salts, harmful metabolic products occurs in the kidneys. Urine enters the bladder through the ureters and is expelled from it. The urinary canal opens outward through an opening located behind the anal. Through these organs, excess salts, water and metabolic products harmful to the body are removed from the body of the fish.

Metabolism - a set of chemical processes occurring in a living organism . Metabolism is based on two phenomena: the construction and decay of organic substances. Complex organic matter, entering the body with food in the process of digestion turn into less complex. They are absorbed into the blood and carried to the cells of the body, where they form the proteins, fats and carbohydrates necessary for the body. This takes energy, which is released during breathing. At the same time, many substances in the cells decompose into water, carbon dioxide and urea. Thus,metabolism consists of the processes of building and breaking down substances .

The metabolic rate of fish depends on body temperature. Fish are cold-blooded animals with variable body temperature. The body temperature of the fish is close to the ambient temperature and does not exceed it by more than 0.5–1.0 degrees (although in tuna, the difference can be up to 10 degrees).

Nervous system is responsible for the coherence of the work of all systems and organs, the implementation of the body's reactions to environmental changes. Like all vertebrates, in fish it consists of the brain, spinal cord (central nervous system) and nerves extending from them (peripheral nervous system).Brain consists of five departments:front , including visual lobes,middle, intermediate, cerebellum And oblong brain. All active pelagic fish have large optic lobes and cerebellum as they require good vision and fine coordination. The medulla oblongata passes into the spinal cord, which ends in the caudal spine.

ri participation nervous system The body responds to various stimuli. This reaction is calledreflex . In the behavior of fish are manifestedunconditional And conditional reflexes. Unconditioned reflexes are otherwise called innate. All animals belonging to the same species unconditioned reflexes appear the same. Conditioned reflexes produced during the life of each fish. For example, by tapping on the glass of the aquarium every time you feed, you can ensure that the fish will begin to gather near the feeder just to knock.

sense organs fish are well developed. The eyes are adapted to clearly recognize objects on close range to distinguish colors. Through the inner ear - an organ located inside the skull - fish perceive sounds. Odors are recognized through the nostrils. In the oral cavity, in the skin of the antennae, lips, there are organs of taste that determine sweet, sour, salty.

The direction and strength of the water current perceiveslateral line . It is formed by a channel passing inside the body, which communicates with the aquatic environment through holes in the scales. Sensory lateral line cells respond to changes in water pressure and transmit signals to the brain.

Features of reproduction and development of fish

Reproductive organs . Almost all fish separate sexes . For reproduction, special paired organs are used: in males -testicles (milk), vas deferens, in females -ovaries , oviducts. In the testes, male germ cells develop - spermatozoa, in the ovaries - female germ cells - eggs (eggs). For their withdrawal, there is a special genital opening. In some species of fish, males and females differ in color and body shape. Biologists call this phenomenon sexual dimorphism.

Sexual dimorphism is manifested in the external differences of individuals of the opposite sex (based on these differences, they recognize and choose each other). A vivid example of sexual dimorphism is an exceptionally peculiar species of males and females of some deep sea fish – anglers .

Small males, only a few centimeters in size, attach themselves to the body of much larger females. Or rather, they grow, because at the same time their circulatory system becomes an appendage of the female's circulatory system. From this point on, males become incapable of independent existence. They are needed only for the production of offspring.

Reproduction and development of fish. With the maturation of germ cells in fish, the instinct of reproduction is manifested. The reproduction of fish is calledspawning . Readiness for spawning is signaled by the behavior of the fish and mating coloration. Some fish are spawningmigration , moving to places more suitable for the development of their future offspring.Salmon, eels and a number of other fish overcome great distances.

Spawning females lay eggs, which are fertilized by males. Fish lay eggs on clusters of algae, lumps of mucus, bubbles of foam at the surface of the water, in pits at the bottom, etc. Fertilization is external - occurs in the environment.

When the sex cells merge, an egg is formed, which matures in water. The embryo develops inside the egg. The mature embryo of the fish is released from the membranes, enters the water and from that moment is called the larva. Over time, the larva begins to feed independently on microscopic algae, ciliates, and then small crustaceans. In case of survival, it becomes like an adult fish, it is calledfry .

In many species of fish, enormous fecundity serves as an adaptation for survival. so femaleriver perch lays 200-300 thousand eggs, femalecarp 400-600 thousand eggs, and the femalecod up to 10 million. There are fish that do not lay a large number of caviar. However, these fish show concern for offspring. For example,stickleback three-spined lays only 60-70 eggs. In a special way, care for the offspring ofseahorses, sea needles, tilapia . There are also viviparous species of fish. With a live birth, the number of born cubs is reduced to tens and units. Some sharks and rays lay eggs with a well-developed large embryo. These eggs have special devices for attaching to plants.

Growing up, fry pass to "adult" life, enter the feeding period. Having reached puberty, the fish begin to reproduce.

The process of reproduction is very significant for the survival of the species. As a result of evolution, fish have developed suchcomplex behaviors , as spawning migrations (salmon, sturgeon, freshwater eel ), care for offspring (three-spined stickleback, seahorse etc.), mating "dances". All these are adaptations of species to living conditions, survival next to other types of organisms.

Migrations. As we found out, the fish are in the process life cycle the following stages pass: egg, larva, fry, fattening, sexually mature individual. Some fish, for examplesalmon , migrations are necessarily present in the life cycle. The first three stages (they take from 2 to 5 years of life) salmon spend in rivers. Then comes the time of the first migration, and juvenile salmon roll down the rivers into the sea. Here, moving and feeding on a vast area, salmon develop rapidly (foraging) and reach sexual maturity.

After that, salmon begin the second (spawning) migration to their native rivers, where they find their way by the smell of water. Fish rise to the upper reaches of the river and spawn. This ends the cycle of reproduction. Weakened parents drift downstream. Many die, but many survive for subsequent migrations and spawning.Far Eastern salmon (pink salmon) dies after spawning. Fish that migrate from rivers to seas or from seas to rivers are calledcheckpoints . These include many types of herring, salmon, sturgeon. These fish, like salmon, breed in rivers and feed in the sea. Anadromous fish need freedom of movement in rivers. Therefore, their survival requires the creation of special devices to help them bypass hydroelectric dams. Some species of fish have special adaptations in the structure of their bodies that allow them to overcome various obstacles and obstacles on the way to spawning grounds.

Migrations of acne. Lives in the rivers of EuropeEuropean river eel . Eels can reach 2 m in length and 6 kg in weight. River eel refers to anadromous fish. The river eel has a juvenile stage, spawning migration and spawning take place in the sea, and growth and fattening take place in fresh water. Eel can stay for a long time in its main habitats - quiet backwaters of rivers. At the onset of puberty, the eel changes appearance (the diameter of the eyes increases, the back turns from olive green to black, and the abdomen becomes silvery white), rolls into the sea and stops eating. It is known that eel spawning migrations in the Baltic Sea pass through coastal waters, and, starting from the North Sea, their trace has not been studied. In the end, the eel ends up at its spawning site: off the coast of America in the Sargasso Sea. Having spawned at a depth of 300–400 m, the eel dies. The larvae emerging from the eggs (they are calledleptocephali ) are so unlike their parents that they were at one time considered a different kind of fish.

These eel larvae, having appeared in the Sargasso Sea, emerge into the upper layers of the water, are picked up by the currents that arise in the western part of the North Atlantic, and drift for 2.5–3 years to the shores of Europe. During this migration, the body of eels undergoes quite complex transformations. Transparent three-year-old eel fry (glass eels) appear in flocks off the coast of Europe. Next, male eels are fattened in brackish waters. And females enter rivers, migrate upstream, settle in various water bodies and live in fresh water for at least a few years. They feed on small fish, caviar, frogs. With the onset of puberty, it is time to go to their native places.

Not all questions related to the long-term migrations of European eels have been clarified. In addition to the river eel, such migrations are characteristic of some species of gobies and tropical species of catfish.

Caring for offspring in seahorses. exemplary father among fish issea ​​Horse . Widespread in the seas and oceans, skates have a solid body covered with plates of the external skeleton. On the abdomen of the male there is a pocket that opens outwards only with a small opening.

For the entire breeding season, the skates form a permanent pair, which occupies a certain area in the sea thickets. If any stranger encroaches on this territory, the male will drive him away. During spawning, the female places eggs inside the male's brood pouch, which develop there. The tissues of the brood pouch contain a large number of small blood vessels through which the eggs are supplied with oxygen. Spawning usually occurs several times, so small skates can be found in the male's pouch. different ages, and then the grown-up generation leaves the father's bag with an interval of several days.

Sometimes the father's concern does not end there, and fully formed young skates that have already left the bag, in case of danger, can again briefly return under the protection of their father.

Live birth. Some species of fish do not lay eggs, but give birth to cubs that have developed inside the mother's body. In this case, the development of the larva occurs directly in the oviducts of the female due to nutrients available in the caviar. TO viviparous species fish are not only sea ​​giants(sharks, rays), but also very small fish (aquariumguppies, swordsmen ).

The value of fish in nature and human life. Protection and breeding of fish

role in nature. About 70% of the Earth's surface is covered with water, or rather, with aquatic biogeocenoses: stable communities of living organisms that have developed in the process historical development Earth. Each species, as an inhabitant of one or another biogeocenosis, has developed characteristic adaptations to life in communities. Each species plays its own unique role here.

In aquatic biogeocenoses, fish enter into various relationships with other organisms. Considering, for example, food chains aquatic biogeocenoses, one can be convinced that fish eat a large number of animal and plant organisms. But they themselves, in turn, serve as food for many other organisms. Relationships in which different types of animals are interconnected with mutual benefit (symbiosis) are very interesting. How does it happen inamphiprion (clown fish) and anemones.

hydroid polyps that help them camouflage themselves on the bottom. Hydroid polyps, in turn, find a means of transportation in fish.

The value of fish in human life.Fishing one of the oldest forms economic activity of people. Fish for humans is a source of very valuable nutrients, mainly animal proteins and fats, and these products are more easily absorbed by the human body than vegetable ones.

Fish (especially bone ones) are of great practical importance for humans. In addition to food, fish serve as a raw material for obtaining medicine ( fish fat etc.), feed for livestock and poultry (feed meal), fertilizers for fields, industrial fat, glue, leather and other materials used in the food and light industries. There are countries where the well-being of the population directly depends on fishing.

Up to 90% of the mass of fish is caught in the seas and oceans. The main objects of the marine industry arecod, haddock, saffron cod, pollock, herring, herring, sardine, sea bass, flounder, saury, mackerel, tuna . In the rivers of Russia they catch sturgeon, salmon,ram, roach, zander and other fish. Meat, fat, caviar are used for food.

Millions of people are engaged in catching, breeding and processing fish, building ships and making fishing equipment.

Hundreds of thousands of people are fond of fishing and spearfishing, to whom this wonderful sport gives health and relaxation. Even more hobbyists are creating a colorful, quiet world in the glass containers of their aquariums.

Fish protection. Marine fisheries are currently experiencing great difficulties. They are associated with pollution. water resources(due to accidents of oil tankers; pollution caused by the development of minerals; discharges of coastal runoff). In addition, using modern powerful means of fishing, you can completely catch all the fish and thereby not only stop further fishing, but also cause irreparable harm to nature. To prevent this from happening, special measures are taken to protect and reproduce fish.

Ecology says: the most unstable factors for the existence of fish today is the purity of the water, air mode, conservation of species habitats. And offers the basic principles of environmentally friendly activities near water bodies and in water bodies.

The basis of the stability of biogeocenoses is the diversity of species. In order for aquatic biocenoses to always exist, it is necessary to conserve fish species by all means, and first of all, those that are threatened with extinction (due to deteriorating environmental conditions, overfishing or other factors).

Laws on the protection and use of the animal world of the planet are adopted by world organizations. In particular, all fishing enterprises, as well as amateur fishermen, are required to strictly observe the established fishing rules. The laws define the methods and seasons of fishing. The diameter of the meshes of the nets should be such as not to impede the exit of juveniles from them. On the rivers and ponds of Russia, the use of nets is strictly prohibited, as well as the killing of fish by explosions (after all, almost the entire population of this section of the reservoir dies). Much attention should be paid to the installation of treatment facilities that prevent water polluted by sewage from factories and factories from entering rivers, lakes and seas.

Valuable fish. Of special scientific and biological value are rare fish world and Russia. Among them, we note species that are found only in a given habitat (they are calledendemic ). Endemic to Russia is, for example,Kaluga , swimming from the sea to the Amur. Many endemic fish species live in Lake Baikal. These species must be protected as a special natural value.

From an industrial point of view, for example, sturgeon and salmon fish. Their meat and caviar are delicious and nutritious!

The features of individual fish species are valued and used by humans. So, exported from Americagambusia settled to fight mosquitoes. After all, she feeds on their larvae.

Variety of fish

Studying the diversity of fish, ichthyologists distribute them into different groups. So, depending on the attitude to the environment, all fish are divided into marine, freshwater and anadromous.

maritime species are the majoritysharks, rays , many herring and other fish.

TO freshwater include, for example, cyprinids:roach, dace, asp, tench, barbel, bream, bleak, sabrefish, carp, crucian carp, grass carp . In fresh waters, an important factor determining the distribution of fish is the flow of water.Bream lives only in running water. Butcrucians, rotans can live in small ponds and swampy lakes.

To those living both in fresh water and in sea ​​water(i.e.checkpoint ) include sturgeon, salmon,freshwater eel etc. Anadromous fish are usually able to adapt to strong fluctuations in water salinity. In addition, during the life cycle, they need to prepare the body for high energy costs associated, for example, with overcoming currents.

In addition, among fish there arepelagic , i.e. living in the water column (herring, horse mackerel, cod, tuna ), And bottom , i.e. living near the bottom (flounder, catfish ).

There are peaceful fishherbivores types (eg. silver carp ) and very aggressivepredators (pike, perch, catfish ).

Class Cartilaginous fish

Fish with a cartilaginous, non-ossifying skeleton are classified asclass Cartilaginous fish . These fish do not have gill covers. On each side of the body, 5–7 pairs of gill slits separated from each other open freely. Among cartilaginous fish three divisions are distinguished:Sharks, Rays, Chimeras .

Shark Squad. There are over 250 species of sharks. Their sizes are different. For example,midget shark , living in the Gulf of Mexico, does not exceed 20 cm in length and weighs no more than 500 g. Awhale shark has a length of 18–20 m and a mass of about 10 tons. The skin of sharks is rough, covered with scales with numerous teeth. The external structure of the shark reflects all the adaptations to life in the water column: a torpedo-shaped body, a sharp nose, dark above and light below the body color.

Paired pectoral and ventral fins provide the shark with up and down movement. The upper lobe of the caudal fin is usually longer than the lower lobe. Vision is black and white. Sharks have a well-developed sense of smell, with which they search for prey. They live mainly in the seas. Most are active predators. They prey on fish, shrimps, aquatic mammals. The whale shark feeds on plankton.herring sharks - viviparous fish. They are found in the Atlantic and Pacific Oceans in temperate and subtropical waters. Most dangerous to humansbrindle And blunt sharks, hammerhead shark, mako And big white . Sharks are an object of fishing. Shark liver is considered a valuable product, which occupies 20-30% of body weight.

Squad Squad. About 350 species of stingrays are known. These are large fish with a flat diamond-shaped body flattened in the dorsal-ventral direction. On the sides it is formed by expanded pectoral fins. When moving, the fins move in waves.

The sizes of the slopes are different. The smallest slopeDiptera from the Yellow Sea - has a width of 10-15 cm. The largest representative of the detachment -manta - in the span of fins reaches 8 m and has a mass of about 2.5 tons.

On the ventral side of the body of stingrays, a transverse mouth opens with a powerful grater of teeth, as well as five pairs of gill slits. Many have spines (skin teeth) on their scales. They feed on bottom animals: mollusks, worms, crabs, fish.

The tail of the stingrays is extended into a whip. At the end of the tail, stingrays have a spike with a poisonous gland.

Some tropical species stingrays have electric organs. Electrical discharges up to 300 volts are produced, probably for protection purposes. The electrical processes in the muscle tissue of rays have not yet been adequately explained. Stingrays are objects of fishing. Some are dangerous to humans.

The Chimera order is a representative of the subclass Whole-Headed or Solid-Cranial. In chimeras, the jaws are completely fused to the skull; in this they strongly resemble bony fish. The gill slits are covered with a skin fold. There is no cloaca, the anal and urogenital openings are separated from each other. A naked body up to 1.5 m long, gradually thinning, passes into a long tail.

It is believed that chimeras originated from ancient sharks and are a side branch of evolution. Wholeheads have been known since the Upper Devonian; at present, only a detachment of chimeras exists. Of more than a dozen of his families, only 3 have survived to this day; about 30 species living from the shelf to great depths of the oceans. Chimeras feed on marine invertebrates and fish. They have practically no commercial value.

Class Bony fish

Bony fish are a class of aquatic vertebrates. All structural features of fish are determined by the environment in which they live. Long-term adaptation to life in the water has not left a single extra detail that interferes with movement.

Body sizes range from 0.7 - 0.9 cm (Philippine goby ) up to 17 m ( herring king ); blue marlin weighs up to 900 kg. The body shape is usually elongated and streamlined, although some bony fish are flattened in the dorsal-ventral direction or from the sides, or vice versa are spherical. The translational movement in the water is carried out due to the wave-like movements of the body. Some fish at the same time "help" themselves with a caudal fin. Paired lateral, as well as dorsal and anal fins serve as stabilizer rudders. In some fish, individual fins have been transformed into suckers or copulatory organs.

Outside, the body of bony fish is covered with scales: placoid (teeth laid "in the parquet"),ganoid (rhombic plates with a spike),cycloid (thin plates with a smooth edge) orctenoid (plates with spines), periodically changing as the animal grows. Annual rings on it allow you to judge the age of the fish.

In many fish, mucous glands are well developed on the skin, their secretions reduce the resistance to the oncoming flow of water. In some deep-sea fish, luminous organs develop on the skin, which serve to identify their species, consolidate the flock, lure prey, and scare away predators. The most complex of these organs are similar to a searchlight: they have luminous elements (such as phosphorescent bacteria), a mirror reflector, a diaphragm or lens, and an insulating black or red coating.

The color of the fish is very diverse. Usually, fish have a bluish or greenish back (the color of the water) and silvery sides and belly (hardly visible against the background of a light "sky"). Many camouflage fish are covered with stripes and spots. The inhabitants of coral reefs, on the contrary, amaze with a riot of colors.

Variety of bony fish

Bony fish include most types of fish. They are subdivided into bone-cartilaginous, lungfish, lobe-finned and bony.

The bone-cartilaginous, or sturgeon, fish includebeluga, sterlet, Russian sturgeon . They have a bone-cartilaginous skeleton with a well-developed chord, there are gill covers, a swim bladder. Along the body of sturgeon there are 5 rows of bone plates, between which are small bone plates. The head, like that of sharks, has an elongated snout. Near the mouth, located on the underside of the head, there are antennae. The caudal fin is unequal.

Sturgeons: beluga (1), Siberian sturgeon (2), sterlet (3), stellate sturgeon (4), common shovelnose (5), paddlefish (6).

Sturgeons are migratory fish of the northern hemisphere. They live up to 50–100 years or more. These fish are widely known for their special tasty meat and black caviar. A typical representative of sturgeons -Russian sturgeon , a common inhabitant of the Volga-Caspian and Black Sea basins. Spends most of the time at sea, spawning in rivers. The sturgeon feeds mainly annelids and shellfish. For the winter, it lies in deep holes, most often in the mouths of rivers. Currently, the number of sturgeons is small.

Lungfish - a small (only 6 species) ancient group of fish. Among themAustralian horntooth, African And south american flake . In lungfish, the notochord is preserved throughout life, the vertebral bodies do not develop, which indicates their antiquity. Unpaired fins have a feathery structure characteristic of the subclass. The upper jaw is fused to the skull. Along with gills, these fish have lungs that have developed from the swim bladder. Some lungfish, rising to the surface, can swallow atmospheric air. The elongated body can reach a length of 2 m. These fish can wait out a long drought by burrowing into the silt. The structure of the heart has also changed: the atrium is divided incomplete septum on the left and right halves. The right half receives blood from the gills, and the left half receives blood from the lungs.

Dipnoi: cattail (barramunda) (7), lepidosirenus (8), large protopter (mamba) (9).

lungfish - freshwater fish living in stagnant or drying up water bodies.

Australian horntooth (more than 1 m long) lives in rivers heavily overgrown with plants. In summer, when the reservoirs become shallow, breaking up into a chain of pits - barrels with rotting water, it completely switches to breathing atmospheric air. Having exposed the snout above the water, it throws out the “exhausted” air with force and at the same time makes a groaning-grunting sound that spreads far around the neighborhood. Horntooth feeds on mollusks, crustaceans, worms, insect larvae.

Other representatives of the lungfish -African flake (up to 2 m long) and South American flake (up to 1 m long) during the drying up of reservoirs they are buried in silt and hibernate.

Loop-finned fish- an ancient group of fish. Until the first half of the XX century. they were considered an extinct branch of vertebrates, once widespread both in fresh water bodies and in the seas. Crossopterans are close to lungfish. Their skeleton was mostly cartilaginous. The notochord was absent in adult fish. The fins of the crossopterans were similar to the fins of the horntooth, the swim bladder turned into a paired lung, and the nostrils communicated with the oropharynx. Currently, one modern representative is known -coelacanth , a descendant of marine crossopterans.

Coelacanth - big fish(up to 180 cm long). Her body is covered with massive scales, and her fins (especially paired ones) look like fleshy lobes. Coelacanths live at the bottom, at a depth of up to 400 m (possibly deeper), in the southwestern part of the Indian Ocean. They feed on fish.

Bony fish - the most numerous group modern fish(about 96% of all species). Their skeleton is ossified, the notochord develops only in embryos, and the scales are bony. They usually have a swim bladder. Bony fish include such valuable commercial species astuna, halibut, salmon, herring, pike and others. Common to our riverscarp And bream - Same bony fish. These fish live in almost all water bodies of the Earth.

Herrings: Atlantic herring (10), Japanese anchovy (11), European sprat (sprat) (12), sardinella (13).

This group includes fishherring detachments (herring, sardines, anchovies , two types of which are called hamsa),salmonids (noble salmon , or salmon, chum salmon, pink salmon, chinook salmon, sockeye salmon, whitefish, grayling, smelt ), cyprinids (chub, roach, bream, ide, dace, asp, carp, crucian carp ), catfish (catfish ), cod-like (cod, saffron cod, haddock, blue whiting, pollock, burbot ), flatfishes (flounder, halibut ). There are more than 40 units in total.

OGE in biology is not included in the list of mandatory ones, but is chosen by students quite often. According to experts, most of the subjects pass the exam in this subject quite successfully, therefore the glory of a relatively easy one has stuck to the subject. Also, a number of 9th grade graduates plan to enter medical schools. Biology is also chosen upon admission to the 10th grade with a certain bias.At the stage of the 9th grade, there is not much material covered, it is quite accessible for understanding and mastering.

In 2018, the minimum threshold was 13 points - in other words, 13 tasks are required to pass the exam for a minimum mark. Maximum - 32 points for an "excellent" rating.
The structure of the biology exam is similar to the rest of the exams:

  • The first part is designed to check the level of knowledge of factual data, laws, terms. These are ordinary test tasks where you need to find the correct answer from the proposed ones, establish correspondence, sequence - the answers are displayed in the answer sheet.
  • The second part is a few tasks that require a detailed answer. It is necessary to solve the problem and describe in detail the course of conclusions.
According to the level of complexity, all tasks are divided into three levels of complexity, which allows you to qualitatively assess the student's preparation and the compliance of his knowledge with the norms and standards of the program: basic, advanced and high.

The first step is to decide on the goal to be achieved. Based on the goal, you can create detailed plan preparation. Without a plan, the process of repetition and study of information will be sketchy, unsystematic, and the result will not be the highest. Familiarization with will allow you to create a plan according to which the preparation will be carried out. It is very important to organize yourself so as not to deviate from the plan, to practice regularly. The best thing is to combine independent work, attentiveness in the classroom and consultation with a teacher or tutor.
I will solve the OGE in biology - this is additional opportunity assess the level of knowledge, consolidate the theory, get used to working with test tasks different types and difficulty levels.
Is it possible to prepare from scratch?
Yes. It takes time, self-discipline and the opportunity to consult with a professional. In this case, it is recommended to hire a tutor and regularly complete assignments online.
It is recommended to start preparation at the beginning of the 9th grade in order to repeat the material for previous years:

  • General biology;
  • Anatomy;
  • Botany;
  • Ecology;
  • Zoology.
Considering the peculiarities of your knowledge, allocate time to repeat all of the listed courses.
The advantages of preparing with online testing: the ability to assess and consolidate knowledge, save time, the ability to immediately calculate points for correct answers, you can use the resource at any time, regardless of where you are.

Very soon, every ninth grade will take exams. They affect not only the matriculation certificate, but also whether the student will enter the tenth grade or go to college. Biology tests at the OGE are simply necessary for future doctors who plan to receive a diploma of a junior medical officer. No wonder most students consider biology the most difficult school discipline. There are many anatomical terms, as well as chemical and biological bases.

Features of the exam in biology

This exam has two parts. The first of them contains twenty-eight tasks, and among which 22 relate to basic level difficulties. The answers to the OGE in biology in the tests in this part should be in the form of a single number, which corresponds to the number of the correct statement.

Another 6 tasks are related to elevated level difficulties. Among them, in two you need to choose and write down three correct answers out of six.

After this stage, proceed to the most difficult stage, namely the second part. It contains four tasks for which you need to give not one letter, but a detailed answer. The OGE in biology will be checked by experts who act in accordance with the main assessment criteria.

How are assignments evaluated?

There is a special table that translates the number of points scored into a five-point system:

  • from 13 to 25 are translated into "3";
  • from 26 to 36 means "4";
  • over 37 - "5".

Converting grades to points

Point conversion scale

For the first twenty-two tasks, each correct answer is worth one point. If this is completely wrong, then the result will be "0". With the correct completion of tasks from 23 to 27, “2” points are given for each correct choice.

Task 28 can even be rated "3". For the next four questions, the score will depend on how complete the answer is disclosed and how correctly it is done.

The maximum number of points that can be scored for the OGE tests in biology is "46". You have three hours to complete this task.

Where is the best place to prepare?

The well-known portal "Dunno" will allow you to go through the buildings in biology online.

Site Dunno

Here you can also download assignments in PDF format and print them out to try to cope with the OGE with a pen. This will help you lose any nerves and feel confident in the exam itself.

Download assignments on the Dunno site

The Yandex OGE website has huge amount tasks and options that need to be solved in the same period of time as a real exam.

Yandex OGE

This will help you train yourself to feel and plan time.

Here, students also have the opportunity to download tests.

Download biology tests

The demonstration version of the OGE in Biology is designed to enable any exam participant and the general public to get an idea of ​​the structure of the future examination work, the number and form of tasks, as well as their level of complexity.

The given criteria for evaluating the performance of tasks with a detailed answer, included in this option, will allow you to get an idea of ​​​​the requirements for the completeness and correctness of writing a detailed answer.

Demo version of the OGE in Biology 2018 (Grade 9)

Changes in KIM OGE 2018 in biology compared to 2017 no

Total tasks - 32; of them by type of tasks: with a short answer - 28; with a detailed answer - 4; by level of difficulty: B - 22; P - 7; AT 3.

Maximum score – 46.

The total time to complete the work is 180 minutes.

Since there are no changes, the demo version of the OGE 2017 is relevant for preparation.

Demo version of the OGE in biology 2017

Additional materials and equipment

Scroll additional materials and equipment, the use of which is allowed at the OGE, approved by order of the Ministry of Education and Science of Russia. It is allowed to use a ruler and a non-programmable calculator in the biology exam.

The examination paper consists of two parts, including 32 tasks.

Part 1 contains 28 short answer tasks, part 2 contains 4 long answer tasks.

Answers to tasks 1-22 are written as a single digit, which corresponds to the number of the correct answer. Write this figure in the answer field in the text of the work, and then transfer it to the answer sheet No. 1.

Answers to tasks 23–28 are written as a sequence of numbers. Write this sequence of numbers in the answer field in the text of the work, and then transfer it to the answer form No. 1.

For tasks 29–32, a detailed answer should be given. Tasks are performed on the answer sheet No. 2.

The system for assessing the performance of individual tasks and the examination work of the OGE in biology as a whole

For the correct execution of each of the tasks 1–22, 1 point is given, in the other case - 0 points.

For the correct execution of each of the tasks 23–27, 2 points are awarded.

For answers to tasks 23 and 24, 1 point is given if the answer contains any two numbers presented in the answer standard, and 0 points in all other cases.

If the examinee indicates more characters in the answer than in the correct answer, then 1 point is reduced for each extra character (up to 0 points inclusive). For the answer to tasks 25 and 27, 1 point is given if one mistake is made, and 0 points if two or more mistakes are made.

For the answer to task 26, 1 point is given if any two positions of the answer do not contain the same character that is presented in the answer standard. If there are more errors, then 0 points are given.

For the complete correct completion of task 28, 3 points are awarded; 2 points if any one position of the answer does not contain the same character that is presented in the standard answer; 1 point is given if any two positions of the answer contain characters other than those presented in the answer standard, and 0 points in all other cases.

Tasks 29-32 are evaluated depending on the completeness and correctness of the answer.

Maximum primary score for the performance of all work - 46