Fish are the oldest vertebrate chordates that inhabit exclusively aquatic habitats, both salt and fresh water. Compared to air, water is a denser habitat.

In the outer and internal structure Fish have adaptations for life in water:

1. Body shape is streamlined. The wedge-shaped head smoothly passes into the body, and the body into the tail.

2. The body is covered with scales. Each scale with its anterior end is immersed in the skin, and with its posterior end it rests on the scale of the next row, like a tile. Thus, the scale is protective cover, which does not interfere with the movement of fish. Outside, the scales are covered with mucus, which reduces friction during movement and protects against fungal and bacterial diseases.

3. Fish have fins. Paired fins (pectoral and ventral) and unpaired fins(dorsal, anal, tail) provide stability and movement in the water.

4. A special outgrowth of the esophagus helps fish to stay in the water column - swimming bladder. It is filled with air. By changing the volume of the swim bladder, fish change their specific gravity (buoyancy), i.e. become lighter or heavier than water. As a result, they can stay at different depths for a long time.

5. The respiratory organs of fish are gills, which absorb oxygen from the water.

6. The sense organs are adapted to life in water. The eyes have a flat cornea and a spherical lens - this allows the fish to see only close objects. The olfactory organs open outward through the nostrils. The sense of smell in fish is well developed, especially in predators. The organ of hearing consists only of the inner ear. Fish have a specific sense organ - the lateral line.

It has the appearance of tubules stretching along the entire body of the fish. Sensory cells are located at the bottom of the tubules. The lateral line of the fish perceive all movements of the water. Due to this, they react to the movement of objects around them, to various obstacles, to the speed and direction of currents.

Thus, due to the peculiarities of the external and internal structure, fish are perfectly adapted to life in the water.

What factors contribute to the onset of diabetes? Explain preventive measures for this disease.

Diseases do not develop on their own. For their appearance, a combination of predisposing factors, the so-called risk factors, is required. Knowledge about the factors in the development of diabetes helps to recognize the disease in a timely manner, and in some cases even prevent it.

Risk factors for diabetes are divided into two groups: absolute and relative.

The group of absolute risk of diabetes mellitus includes factors associated with heredity. This is a genetic predisposition to diabetes, but it does not give a 100% prognosis and a guaranteed undesirable outcome. For the development of the disease, a certain influence of circumstances is necessary, environment, manifested in relative risk factors.

Relative factors in the development of diabetes include obesity, metabolic disorders, and a number of concomitant diseases and conditions: atherosclerosis, coronary heart disease, hypertension, chronic pancreatitis, stress, neuropathy, strokes, heart attacks, varicose veins veins, vascular damage, edema, tumors, endocrine diseases, long-term use of glucocorticosteroids, old age, pregnancy with a fetus weighing more than 4 kg, and many, many other diseases.

Diabetes - This is a condition characterized by high blood sugar levels. The modern classification of diabetes mellitus, adopted World Organization health care (WHO), distinguishes several of its types: 1st, in which the production of insulin by pancreatic b-cells is reduced; and the 2nd type is the most common, in which the sensitivity of body tissues to insulin decreases, even with its normal production.

Symptoms: thirst, frequent urination, weakness, complaints of itchy skin, weight change.

The amazing variety of shapes and sizes of fish is explained by the long history of their development and high adaptability to the conditions of existence.

The first fish appeared several hundred million years ago. Now existing fish bear little resemblance to their ancestors, but there is a certain similarity in the shape of the body and fins, although the body of many primitive fish was covered with a strong bony shell, and highly developed pectoral fins resembled wings.

ancient fish became extinct, leaving their traces only in the form of fossils. From these fossils, we make guesses, assumptions about the ancestors of our fish.

It is even more difficult to talk about the ancestors of fish that left no traces. There were also fish that had no bones, no scales, no shells. Similar fish still exist. These are lampreys. They are called fish, although, in the words of the famous scientist L. S. Berg, they differ from fish, like lizards from birds. Lampreys do not have bones, they have one nasal opening, the intestines look like a simple straight tube, the mouth is in the form of a round sucker. In the past millennia, there were many lampreys and related fish, but they are gradually dying out, giving way to more adapted ones.

Sharks are also fish ancient origin. Their ancestors lived more than 360 million years ago. The internal skeleton of sharks is cartilaginous, but there are solid formations in the form of spikes (teeth) on the body. In sturgeons, the body structure is more perfect - there are five rows of bone bugs on the body, there are bones in the head section.

According to the numerous fossils of ancient fish, one can trace how the structure of their body developed and changed. However, it cannot be assumed that one group of fish directly converted to another. It would be a gross mistake to say that sturgeons originated from sharks, and teleosts from sturgeons. We must not forget that, in addition to the named fish, there were a huge number of others, which, unable to adapt to the conditions of the nature surrounding them, died out.

modern fish also adapt to natural conditions, and in the process of this, slowly, sometimes imperceptibly, their lifestyle and body structure change.

An amazing example of high adaptability to environmental conditions is represented by lungfish. Ordinary fish breathe with gills, which consist of gill arches with gill rakers and gill filaments attached to them. Lungfish, on the other hand, can breathe with both gills and “lungs” - peculiarly arranged swimming ones and hibernates. In such a dry nest, it was possible to transport protopterus from Africa to Europe.

Lepidosiren inhabits swampy water bodies South America. When reservoirs are left without water during a drought lasting from August to September, lepidosiren, like protopterus, burrows into silt, falls into a stupor, and its life is supported by bubbles. The bubble-lung of lungfish is replete with folds and partitions with many blood vessels. It resembles an amphibian lung.

How to explain this structure of the respiratory apparatus in lungfish? These fish live in shallow water bodies, which dry out for quite a long time and become so poor in oxygen that breathing with gills becomes impossible. Then the inhabitants of these reservoirs - lungfish - switch to breathing with the lungs, swallowing the outside air. When the reservoir completely dries up, they burrow into the silt and experience drought there.

There are very few lungfish left: one genus in Africa (protopterus), another in America (lepidosiren) and a third in Australia (neoceratod, or scaly).

Protopterus inhabits fresh water bodies of Central Africa and has a length of up to 2 meters. During the dry period, it burrows into the silt, forming a chamber (“cocoon”) of clay around itself, content with an insignificant amount of air penetrating here. Lepidosiren- big fish reaching 1 meter in length.

The Australian flake is somewhat larger than the lepidosiren, lives in quiet rivers, heavily overgrown with aquatic vegetation. When the water level is low (dry weather) time) the grass begins to rot in the river, the oxygen in the water almost disappears, then the flake plant switches to breathing atmospheric air.

All listed lungfish are consumed by the local population for food.

Each biological feature has some significance in the life of the fish. What kind of appendages and adaptations do fish have for protection, intimidation, attack! A wonderful device has a small bitter fish. By the time of reproduction, a long tube grows in the female bitterling, through which she lays eggs in the cavity of a bivalve shell, where the eggs will develop. This is similar to the habits of a cuckoo, throwing its eggs into other people's nests. It is not so easy to get mustard caviar from hard and sharp shells. And the bitter man, having dumped his care on others, hurries to put away his cunning device and again walks in the free space.

In flying fish, capable of rising above the water and flying over fairly long distances, sometimes up to 100 meters, the pectoral fins have become like wings. Frightened fish jump out of the water, spread their fins-wings and rush over the sea. But an air walk can end very sadly: birds of prey often attack the little birds.

Flies in temperate and tropical parts Atlantic Ocean and in the Mediterranean. Their size is up to 50 centimeters V.

Longfins living in tropical seas are even more adapted to flying; one species is also found in the Mediterranean Sea. Longfins are similar to herring: the head is sharp, the body is oblong, the size is 25-30 centimeters. The pectoral fins are very long. Longfins have huge swim bladders (the length of the bladder is more than half the length of the body). This device helps the fish stay in the air. Longfins can fly over distances exceeding 250 meters. When flying, the fins of longfins, apparently, do not wave, but act as a parachute. The flight of a fish is similar to the flight of a paper dove, which is often launched by children.

Jumping fish are also wonderful. If in flying fish the pectoral fins are adapted for flying, then in jumpers they are adapted for jumping. Small jumping fish (their length is not more than 15 centimeters), living in coastal waters mainly indian ocean, can leave water for quite a long time and get their own food (mainly insects), jumping on land and even climbing trees.

The pectoral fins of jumpers are like strong paws. In addition, the jumpers have another feature: the eyes placed on the head outgrowths are mobile and can see in the water and in the air. During a land journey, the fish tightly covers the gill covers and thus protects the gills from drying out.

No less interesting is the creeper, or climbing perch. This is a small (up to 20 centimeters) fish that lives in the fresh waters of India. main feature its consists in the fact that it can crawl away on land to a long distance from water.

Creepers have a special supra-gill apparatus, which the fish uses when breathing air in cases where there is not enough oxygen in the water or when it moves overland from one reservoir to another.

aquarium fish macropods, fighting fish and others also have a similar supragillary apparatus.

Some fish have luminous organs that allow them to quickly find food in the dark depths of the seas. Luminous organs, a kind of headlights, in some fish are located near the eyes, in others - at the tips of the long processes of the head, and in others, the eyes themselves emit light. An amazing property - the eyes both illuminate and see! There are fish emitting light whole body.

In tropical seas, and occasionally in the waters of the Far Eastern Primorye, one can find interesting sticky fish. Why such a name? Because this fish is able to stick, stick to other objects. There is a large suction cup on the head, with the help of which the stick sticks to the fish.

Not only does the sticky use free transport, the fish also receive a “free” lunch, eating the remnants of the table of their drivers. The driver, of course, is not very pleasant to travel with such a “rider” (the length of the stick reaches 60 centimeters), but it is not so easy to get rid of it either: the fish sticks tightly.

Shore dwellers use this ability to trap turtles. A cord is tied to the tail and the fish is put on the turtle. The sticky stick quickly sticks to the turtle, and the fisherman lifts the stuck stick together with the prey into the boat.

In the fresh waters of the basins of the tropical Indian and Pacific Oceans live small fish archers. The Germans call it even more successful - "Schützenfish", which means a shooter-fish. The archer, swimming near the shore, notices an insect sitting on the coastal or water grass, draws water into his mouth and lets a stream into his "trading" animal. How not to call a archer a shooter?

Some fish have electrical organs. Known American electric catfish. The electric stingray lives in the tropical parts of the oceans. Its electric shocks can knock a grown man off his feet; small aquatic animals often die from the blows of this stingray. Electric Stingray- I rather large animal: up to 1.5 meters in length and up to 1 meter wide.

Strong electric shocks capable of inflicting and electric eel reaching 2 meters in length. A German book depicts frenzied horses attacking electric eels in the water, although there is no small part of the artist's imagination here.

All of the above and many other features of fish have been developed over thousands of years as necessary means of adaptation to life in the aquatic environment.

It is not always so easy to explain why one or another device is needed. Why, for example, does a carp need a strong serrated fin ray, if it helps to entangle the fish in the net! Why are such long tails wide mouth and whistle? Undoubtedly, this has its own biological meaning, but not all the mysteries of nature have been solved by us. We have given a very small number of curious examples, but they all convince of the expediency of various adaptations of animals.

In flounder, both eyes are on one side of a flat body - on the one that is opposite to the bottom of the reservoir. But they will be born, come out of eggs, flounders with a different arrangement of eyes - one on each side. In larvae and fry of flounder, the body is still cylindrical, and not flat, like in adult fish. The fish lies on the bottom, grows there, and its eye from the bottom side gradually passes to the upper side, on which both eyes eventually end up. Surprising but understandable.

The development and transformation of the eel is also surprising, but less understood. The eel, before acquiring its characteristic serpentine form, undergoes several transformations. At first it looks like a worm, then it takes the form of a tree leaf and, finally, the usual shape of a cylinder.

In an adult eel, the gill slits are very small and tightly covered. The feasibility of this device is that it is tightly covered. the gills dry much more slowly, and with moistened gills, the eel can remain alive for a long time without water. There is even a rather plausible belief among the people that the eel crawls through the fields.

Many fish are changing before our eyes. The offspring of large crucian carp (weighing up to 3-4 kilograms), transplanted from the lake into a small pond with little food, does not grow well, and adult fish look like “dwarfs”. This means that the adaptability of fish is closely related to high variability.

I, Pravdin "The story of the life of fish"

Section 1. Adaptations for swimming.

There are many difficulties in swimming. For example, in order not to drown, a person must constantly move, or at least make an effort. But how does the most common river pike hang in the water and not sink? Conduct an experiment: take a thin, light stick and hold it in the air. Not difficult? And try to spend in the water. It's more difficult, right? And the fish always move in the water, and nothing! These are the questions that will be answered in this section.
The first question is why fish don't drown. Yes, because they have a swim bladder - a modified lung filled with gas, fat or some other filler that provides buoyancy to the body of the fish. It is located under the spine, supporting it as the heaviest element of the body. Cartilaginous animals do not have this bubble, so sharks and chimeras are forced to move most of the time. Only a few sharks have primitive bladder substitutes. Previously, it was believed that sharks would not be able to breathe if they stopped, but this is not the case - sharks are not averse to lying on the bottom of the grotto and, which is not excluded, even sleep (although it is possible that only exhausted or sick individuals "rest" in the grottoes). Only stingrays do not care about the absence of a swim bladder - they, lazy, love to lie on the bottom. As for the teleosts, only a few species do not have a swim bladder, including bladderless perches of the scorpion family, all representatives of the flounder and fused gills. The swim bladder may consist of several chambers (cyprinids).

The second issue is light movement in the water. Try to take a board or a flat plate floating on the water, put it on the water and try, without changing the position, to "push" it into the water. She will wag, and only then will succumb. Therefore, to solve this issue, nature gave the fish a streamlined shape, that is, the body became pointed from the head, voluminous towards the middle and tapering towards the tail. But the problem was not completely solved: water is an incompressible medium. But the fish overcame this too: they began to swim in waves, pushing the water first with their heads, then with their bodies, and then with their tails. The discarded water flows down the sides of the fish, pushing the fish forward. And those fish that do not have this shape - scorpion fish, angler, carpet shark, stingray, flounder, etc. - and do not need it: they are bottom fish. Sitting on the bottom all your life, you can do without streamlining. If you need to move, then the stingray, for example, swims, making wave-like movements with its fins (see illustrations).
Let us dwell on the question of the integument of fish. There are four main types of fish scales and many secondary ones, as well as various spikes and spines. The placoid scale resembles a plate with a tooth; cartilaginous are covered with such scales. Ganoid scales, diamond-shaped and covered with a special substance - ganoin - is a sign of some primitive

ray-finned, including shellfish. Bone plates up to 10 cm in diameter - bugs - form 5 longitudinal rows on the skin of the sturgeon, this is all that remains of its scales (yes, it doesn’t have scales - it doesn’t even have teeth, only fry have weak teeth). Small plates and individual scales scattered over the body can be ignored. Ctenoid scales differ from cycloid scales only in that ctenoid scales have a serrated outer edge, and cycloid ones are smooth. These two types are common among most ray-finned animals (including the most primitive ones, such as the cycloid-covered amia). For the ancient lobe-finned, cosmoid scales were characteristic, consisting of four layers: surface enamel-like, the second - spongy-bone, the third - bone-spongy and the lower - dense bone. It has been preserved in coelacanths; in modern dipnoes, two layers have disappeared. Many fish have spines. Pointed bone plates cover the catfish with prickly armor. Some fish have poisonous thorns (about these fish in the second part of the chapter "Dangerous Fish"). A kind of "brush" of spikes on the back and a lot of spikes covering the head are signs of the ancient stetacanthus shark (more details -).
The limbs of fish that help when swimming are fins. Bony fish have spiny teeth on their backs. dorsal, and after it - a soft dorsal fin. Sometimes there is only one dorsal fin. Near the gill covers on both sides are the pectoral fins. At the beginning of the belly, bony fish have paired ventral fins. Near the urinary and anal openings is the anal fin. The "tail" of a fish is the caudal fin. In cartilaginous fish (sharks), everything is almost the same, only some deviations, but we will not consider them. Modern lampreys and hagfishes have a dorsal prefin and a caudal prefin.
Now let's talk about what helps fish live in the underwater world.

Section 2. Mimicry of fish.

Mimicry - the ability to merge with the background, to be invisible. In this section, I will talk about fish mimicry.

rag-picker

In the first (or one of the first) places in terms of mimicry are fish of the stickleback order - Sea Horses and needles. Skates can change color depending on the algae on which they "sat down". Algae is yellow, dry - and the seahorse is yellow, algae is green - the seaweed is green, algae is red, brown - and the seaweed is red or brown. Sea needles do not know how to change color, but they can, swimming in green algae (the needles themselves are green), imitate them so deftly that you cannot distinguish them from algae. And one skate - a rag-picker - will be saved even without hide and seek in algae. It looks like it's all torn, tattered. If he swims, it is not difficult to mistake him for a rag or a piece of seaweed. Rag-pickers are most diverse off the coast of Australia.
The flounders are no worse at hiding. They are flattened laterally, and have both eyes on the side opposite the sand on which they lie. They are better at camouflage than skates, taking on almost any color. On the sand they are sandy, on a gray stone they are gray. They even tried to put flounder on a chessboard. And she became a black and white box!
I talked about the mimicry of scorpionfish and carpet sharks a little earlier. Many fish (such as the Sargassum clown coralfish) camouflage themselves like sea ​​needles, under the surrounding algae or corals.
The mimicry of stingrays is very "cunning". They do not change color, do not imitate algae. They, lying on the bottom, simply cover themselves with a layer of sand! That's the whole disguise.

Section 3. Feelings: sixth, seventh...

If you have an aquarium at home, you can conduct a simple experiment. Make a "swimming cap" for each fish, which is worn on the fish's head (with cutouts for the eyes, mouth, gills and fins). Dip your finger in the water. Did the fish run away? And now put on them "hats" and again dip in

finger water. You will certainly be surprised by the abnormal reaction of the fish, who were not at all afraid of an unfamiliar object and even allowed themselves to be touched. It's all about the "sixth sense" of fish, the SIDELINE system (seismosensory system, or seismosensory sense). The system of channels, called the "lateral line", runs through the entire body of the fish as a series of scales, different from the cover of the whole body, and allows you to perceive all the movements of the water. The "cap" blocks the organs of the lateral line of the head, and the fish does not feel the approach of a foreign object. It is the existence of the lateral line that explains why schools of fish instantly change direction as a whole, and no fish moves slower than the rest. The lateral line is present in all bony and cartilaginous fish, with rare exceptions (brachidanio from the carp family), and also - inherited from fish ancestors - in aquatic amphibians.
But the organs of the lateral line seemed not enough to sharks! And they had a "seventh sense". In the skin of any shark, you can find several pouches lined inside, called ampoules of Lorenzini. They open with canals on the head and underside of the sharks' snout. Ampoules of Lorenzini are sensitive to electric fields, they seem to "scan" the bottom of the reservoir and can detect any Living being, even hidden in a secluded place. It is in order to "scan" as much of the bottom as possible with the help of ampoules that the hammerhead fish has such a head shape. In addition, the ampullae of Lorenzini allow sharks to navigate by the Earth's magnetic field. Of course, stingrays, descendants of sharks, also have ampoules of Lorenzini.

Section 4. Polar fish, or these amazing nototheniids

Fish that live in some unusual conditions often have unusual adaptations to them. As an example, I will consider amazing fish suborder notothenia (perch-like detachment), living not just anywhere, but in ANTARCTICA.
In the seas of the icy continent there are 90 species of nototenidae. Their adaptation to an unfriendly environment began when the mainland of Antarctica became such, separating from Australia and South America. Theoretically, a fish can survive when the blood is one degree colder than the freezing point. But there is ice in the Antarctic, and it penetrated through the covers into the blood of the fish and caused the body fluids to freeze even when hypothermia was even 0.1 degrees. Therefore, in the blood of notothenia fish, special substances called ANTIFREEZES began to be produced, which provide more low point freezing - they simply do not allow ice crystals to grow. Antifreezes are found in all body fluids, except eye fluid and urine, in almost all Nototheniaceae. Due to this, they freeze at water temperature (at different types) from -1.9 to -2.2 degrees Celsius, while ordinary fish - at -0.8 degrees. (Water temperatures in, say, McMurdo Bay near Antarctica are -1.4 to (rarely) -2.15 degrees.)
The kidneys of nototheniids are arranged in a special way - they excrete exclusively waste from the body, while leaving antifreeze "on duty". Thanks to this, fish save energy - after all, it is less common to develop new "substances-saviors".
In addition, there are many more amazing adaptations among the Notothenians. Here, for example, in some species the spine is hollow, and in the subcutaneous layer and small deposits among the muscle fibers there are special fats - triglycerides. This contributes to buoyancy, which becomes almost neutral (i.e. the specific gravity of the fish is equal to the specific gravity of water, and the fish in its environment is actually weightless).

Section 5. Tilapia, or some like it hot.

At the end of the chapter, let's fast forward from ice waters Antarctica to the hot springs of Africa and look at the fish that managed to adapt to these difficult conditions. You can spot fish while swimming in such a spring - a sudden slight tickle probably means that a flock of tiny tilapias are interested in you.

During its existence, the water of many African lakes was so saturated with alkalis that fish simply could not live there. The tilapias of lakes Natron and Magadi had to go into the hot waters of drinking lakes in order to survive. There they have adapted so much that they die in a cool fresh water. However, if heavy rainfall makes the water of the lakes more desalinated for a while, the number of tilapia increases, the fry literally swarm at the border of the source and the lake itself. In 1962, for example, thanks to the rains, tilapia filled the lake so much that lovers of our fish, pink pelicans, even tried to nest on it. However, she went again black line"- either there was not enough oxygen in the water, or the amount of alkalis increased again, but one way or another, all the fish in the lake died. Is it necessary to explain that the nesting of pelicans did not arise there?
Only one species of tilapia, Tilapia grahami, has adapted to life in hot springs. However, there are SIX HUNDRED other varieties of these African fish. Some of them are very interesting. So, Mozambican tilapia is bred in artificial ponds. However, the main "dignity" of tilapia for a zoologist is that it bears eggs IN THE MOUTH!

Fish - inhabitants of the aquatic environment

Fish live in water, water has a significant density and it is more difficult to move in it than in air.

What kind of fish should be in order to survive in the aquatic environment?

Fish are characterized by:

• Buoyancy
• streamlining
• Slip
• Infection protection
• Orientation in the environment

Buoyancy

1. Spindle-shaped body
2. The body is laterally compressed, streamlined
3. Fins

Streamline and glide:

Tiled scales

germicidal mucus

Fish movement speed

The fastest fish sailfish.She swims faster than a cheetah runs.

The speed of a sailboat fish is 109 km/h (for a cheetah it is 100 km/h)

Merlin - 92 km / h

Fish - wahoo - 77.6 km / h

Trout - 32 km / h faster than pike.

Madder - 19 km/h faster

Pike - 21 km/h

Karas - 13 km / h

And did you know that…

The silvery-white color of fish and the luster of scales largely depend on the presence of guanine in the skin (an amino acid, a breakdown product of proteins). The color changes depending on the living conditions, age, and health of the fish.

Most fish have a silvery color and at the same time the abdomen is light and the back is dark. Why?

Protection from predators - dark back and light abdomen

Sense organs of fish

Vision

The eyes of fish can only see at close range due to the spherical lens close to the flat cornea, which is an adaptation for vision in the aquatic environment. Usually the eyes of the fish are “set” for vision at 1 m, but due to the contraction of smooth muscle fibers, the lens can be pulled back, which achieves visibility at a distance of up to 10-12 m.

2) German ichthyologists (scientists who study fish) have found that fish distinguish colors well, incl. and red.

Flounder bypasses red, light green, blue and yellow nets. But the fish probably does not see gray, dark green and blue nets.

Smell and taste

1) The taste organs of fish are located in the mouth, on the lips, on the scalp, body, on the antennae and on the fins. They determine, first of all, the taste of water.

2) The organs of smell are paired sacs in the front of the skull. Outward they open with nostrils. The sense of smell in fish is 3-5 times finer than in dogs.

The presence of vital substances of fish can be established at a distance of 20 km. Salmon catches the smell of the native river from a distance of 800 km from its mouth

Lateral line

1) A special organ runs along the sides of the fish - the lateral line. It serves as an organ of balance and for orientation in space.

Hearing

Scientist Karl Frisch studied not only vision, but also hearing of fish. He noticed that his blind fish for experiments always surfaced when they heard the whistle. Pisces hear very well. Their ear is called the inner ear and is located inside the skull.

Norwegian scientists have found that some species of fish are able to distinguish sound vibrations from 16 to 0.1 Hz. This is 1000 times greater than the sensitivity of the human ear. It is this ability that helps fish to navigate well in muddy water and at great depths.

Many fish make sounds.

Sciens purr, grunt, squeak. When a flock of sciens swims at a depth of 10-12m, lowing is heard

Marine midshipman - hisses and croaks

Tropical flounders make the sounds of a harp, bell ringing

Talk like fish

Dark carp - Khryap-khryap

Light croaker - try-try-try

Guinea cock - track-track-track or ao-ao-xrr-xrr-ao-ao-hrr-hrr

River catfish - oink-oink-oink

Sea carp - quack-quack-quack

Sprats - u-u-u-u-u-u

Cod - chirp-chirp-chirp (quietly)

Herring - whisper softly (tsh - tsh-tsh)

Open lesson in biology in grade 7

Topic: “Superclass Pisces. Adaptations of fish to the aquatic environment

Purpose: To reveal the features of the internal and external structure fish in connection with the habitat, show the diversity of fish, determine the importance of fish in nature and human activities, indicate necessary measures for the protection of fish resources.

Methodological goal: the use of ICT - as one of the ways to form creative thinking and develop the interest of students, expand experience research activities, on the basis of previously acquired knowledge, the development of information and communication competencies.

Lesson type: combined.

Type of lesson: a lesson in the formation and systematization of knowledge.

Lesson Objectives:

Tutorials: to form knowledge about the general characteristics of fish, the features of the external structure of fish in connection with the aquatic habitat.

Developing: develop the ability to observe, establish cause-and-effect relationships, continue the formation of skills to work with a textbook: find answers to questions in the text, use text and drawings to perform independent work.

Educational: education of diligence, independence and respect when working in pairs and groups.

Tasks: 1) To acquaint students with the structural features of fish.

2) Continue the formation of the ability to observe the living

Organisms, work with the text of the textbook, perceive

Educational information through multimedia presentation and video.

Equipment: computer, multimedia projector,

Lesson plan:

Organizing time

Calling Interest

Goal setting.

Exploring a new topic

Operational-cognitive

Reflection

During the classes

Teacher activity

Student activities

1. Organizational.

2 minutes

Greets students, checks the readiness of the workplace for the lesson, creates a favorable relaxed atmosphere.

Divides into groups

Greet teachers, check the availability of didactic materials

to work for a job.

Divided into groups

2. Call of Interest

3 min

Black box game

1. There is evidence that these animals were bred back in Ancient Egypt over four thousand years ago. In Mesopotamia they were kept in ponds.

Kept in Ancient Rome and Greece.

In Europe, they first appeared only in the 17th century.

They first came to Russia from China as a gift to Tsar Alexei Mikhailovich. The king ordered them to be planted in crystal bowls.

IN good conditions content can live up to 50 years.

fairy tale character fulfilling wishes.

2. There is such a zodiac sign

Teacher: - So who will we meet today at the lesson?

Students provide answers after each question.

Pupils: - a goldfish.

And set the topic of the lesson.

3. Goal setting

Purpose: to activate cognitive interest in the topic under study.

1) Let's get acquainted with the structural features of fish.

2) Let's continue the formation of the skills to observe living organisms, work with the text of the textbook, perceive

1) Study the structural features of fish.

2) They will work with the text of the textbook, perceive

learning information through a multimedia presentation.

4. Learning a new topic.

Operational-cognitive.

Purpose: using various forms and methods of work to form knowledge about the external and internal structure of fish

15 minutes

Guys today we will get acquainted with the most ancient vertebrates. Superclass of fish. This is the most numerous class of chordates. There are about 20 thousand species. The section of Zoology that studies fish is called Ichthyology.

Stage I - Challenge (motivation).

Teacher: Sometimes they say about a person: "Feels like a fish in water." How do you understand this expression?

Teacher: Why do fish feel good in the water?

Teacher: What is the adaptability of fish to the aquatic environment? We will learn this during today's lesson.

Stage II - content.

What Features of the aquatic habitat can we name:

1 task. Watch video fragment.

With the help of the textbook and additional text, using the Fishbone technique, describe the adaptation of fish to life in the aquatic environment.

listen

Estimated responses of students (it means he is well, comfortable, everything works out for him).

(It is adapted to life in water).

The children write the topic of the lesson in a notebook.

The high density of water makes active movement difficult.

Light penetrates the water only to a small depth.

Limited amount of oxygen.

Water is a solvent (salts, gases).

Thermal conductivity ( temperature regime softer than on land).

Transparency. Fluidity.

Conclusion : the adaptability of fish to life in water is manifested in the streamlined shape of the body, smoothly passing organs of the body, patronizing coloration, features of integument (scales, mucus), sensory organs (lateral line), organs of locomotion (fins).

- What is the body shape of a fish and how is it adapted to its environment?

Teacher addition.Man arranges for his movement in the water, sharpening the noses of his boats and ships, and during construction submarines gives them a spindle-shaped, streamlined shape of a fish body). The shape of the body can be various spherical (hedgehog fish), flat (stingray, flounder), serpentine (eels, moray eels).

What are the features of the integument of the body of a fish?

What is the significance of the mucous film on the surface of the fish?

Teacher addition. This mucus film helps to reduce friction when swimming, and due to its bactericidal properties, it prevents bacteria from penetrating the skin, because. fish skin is permeable to water and some substances dissolved in it (hormone of fear

WHAT IS THE “FEAR SUBSTANCE”
In 1941 Nobel Laureate Karl von Frisch, studying the behavior of fish, found that when a pike grabs a minnow, some substance enters the water from the wounds on its skin, which causes a fear reaction in other minnows: they first rush in all directions, and then huddle together in a dense flock and stop feeding for a while.

In modern scientific literature instead of the phrase “substance of fear”, you can often find the term “anxiety pheromone”. In general, pheromones are such substances that, being released into the external environment by one individual, cause some specific behavioral reaction in other individuals.

In fish, alarm pheromone is stored in special cells located in the very top layer skin. They are very numerous and in some fish can occupy more than 25% of the total volume of the skin. These cells have no connection with external environment, so that their contents can get into the water only in one case - if the skin of the fish receives some kind of damage.
IN most alarm pheromone cells are concentrated on the front of the fish's body, including the head. The farther back, to the tail part of the body, the fewer cells with pheromone.

What are the color features of the fish?

Bottom fish and fish of grassy and coral thickets often have a bright spotted or striped coloration (the so-called “dissected” coloring masks the contours of the head). Fish can change their color depending on the color of the substrate.

What is a sideline and what is its significance?

Drawing up a common Fishbone at the blackboard .

The fish swims in the water quickly and nimbly; she easily cuts through the water due to the fact that her body has a streamlined shape (in the form of a spindle), more or less compressed from the sides.

Reduced water friction

The body of the fish is mostly covered with hard and dense scales that sit in the folds of the skin (How are our nails? , and the free ends lean on each other, like tiles on a roof. The scales expand with the growth of the fish, and in the light we can see concentric lines resembling growth rings on tree sections. From the growths of concentric stripes, one can determine the age of the scales, and at the same time the age of the fish itself. Additionally, the scales are covered with mucus.

Body coloration. In fish, the back is dark, and the abdomen is light. The dark color of the back makes them hardly noticeable against the background of the bottom when viewed from above, the brilliant silvery color of the sides and abdomen makes the fish invisible against the background of a light sky or sun glare when viewed from below.

Coloring makes the fish hardly noticeable against the background of the habitat.

Lateral line. With the help of it, fish navigate in water flows, perceive the approach and removal of prey, a predator or a partner in a flock, and avoid collisions with underwater obstacles.

PHYS. MINUTE

Purpose: to maintain health.

3 min

Do exercises.

12 min

What other adaptations do fish have for life in the water?

To do this, you will work in small groups. Do you have on your tables additional material. You must read the text material, answer the questions and indicate the structural features of the fish in the picture.

Distribute the task to each group:

"1. Read the text.

2. Look at the drawing.

3. Answer the questions.

4. Indicate the structural features of the fish in the figure.

Group 1. Organs of movement of fish.

2. How do they work?

Group 2 Respiratory system of fish.

Group 3. Sense organs of fish.

1. What sense organs does a fish have?

2. Why are sense organs needed?

Students organize the search and exchange of ideas through dialogue.Work is being done to complete the drawing.

4. Reflective-evaluative.

Purpose: to determine the level of knowledge gained in the lesson.

7 min

Mission "Fishing"

1. What departments does the body of a fish consist of?

2. With the help of what organ does the fish perceive the flow of water?

3. What structural features of a fish help it overcome water resistance?

4. Does the fish have a passport?

5. Where is the substance of fear found in fish?

6. Why do many fish have a light belly and a dark back?

7. What is the name of the section of zoology that studies fish?

8. Why do flounder and stingray have a flat body shape?

9. Why can't fish breathe on land?

10. What sense organs do fish have?

11. Which fish fins are paired? Which fish fins are not paired?

12. What fins do fish use for oars?

Each team chooses a fish and answers questions.

3 min

There is a drawing of a fish on the board. The teacher offers to evaluate today's lesson, what new things have you learned, etc.

1. Today I learned…

2. It was interesting...

3. It was hard...

4. I learned...

5. I was surprised ...

6. I wanted ...

On multi-colored stickers, children write what they liked most in the lesson, what they learned new and stick them on the fish in the form of scales.

5. Homework.

Describe the internal structure of a fish.

Compose a crossword.

write down homework in a diary.

Group 1. The musculoskeletal system of fish.

1. What organs are the organs of fish movement?

2. How do they work?

3. What groups can they be divided into?

Fin - This is a special body necessary for coordinating and controlling the process of movement of fish in the water. Each fin consists of a thin leathery membrane, which, whenwhen the fin is extended, it stretches between the bony fin rays and thereby increases the very surface of the fin.

The number of fins in different species can be different, and the fins themselves can be paired and unpaired.

In river perch, unpaired fins are located on the back (there are 2 of them - large and small), on the tail (large two-lobed caudal fin) and on the underside of the body (the so-called anal fin).

Paired are the pectoral fins (this is the front pair of limbs), as well as the ventral fins (the rear pair of limbs).

tail fin plays important role in the process of moving forward, paired ones are necessary for turning, stopping and maintaining balance, dorsal and anal help the perch to maintain balance during movement and during sharp turns.

Group 2Respiratory system of fish.

Read the text. Consider the drawing. Answer the questions.

Indicate the structural features of the fish in the picture.

1. What organs make up respiratory system fish?

2. What is the structure of the gills?

3. How does fish breathe? Why can't fish breathe on land?

The main respiratory organ of fish is the gills. The oblique base of the gill is the gill arch.

Gas exchange occurs in the gill filaments, which have many capillaries.

Gill rakers "filter" the incoming water.

The gills have 3-4 gill arches. On each arc there are on one side bright redgill filaments , and on the other hand, gill rakers . Outside gills coveredgill covers . Between the arcs are visiblegill slits, that lead to the throat. From the pharynx, captured by the mouth, water washes the gills. When the fish presses the gill covers, water flows through the mouth to the gill slits. Oxygen dissolved in water enters the blood. When a fish lifts its gill covers, water is forced out through the gill slits. Carbon dioxide is released from the blood into the water.

Fish cannot be on land because the gill plates stick together and air does not enter the gill slits.

Group 3.Sense organs of fish.

Read the text. Consider the drawing. Answer the questions.

Indicate the structural features of the fish in the picture.

1. What organs make up nervous system fish?

2. What sensory organs does a fish have?

3. Why do we need sense organs?

The fish has sense organs that allow fish to navigate well in the environment.

1. Vision - eyes - distinguishes the shape and color of objects

2. Hearing - the inner ear - hears the steps of a person walking along the shore, the ringing of a bell, a shot.

3. Smell - nostrils

4. Touch - tendrils.

5. Taste - sensitive cells - all over the surface of the body.

6. Lateral line - a line along the entire body - perceives the direction and strength of the water current. Thanks to the lateral line, even a blinded fish does not run into obstacles and is able to catch moving prey.

On the sides of the body in scales, a lateral line is visible - a kind of organfeelings in fish. It is a channel that lies in the skin and has many receptors that perceive the pressure and force of the flow of water, electromagnetic fields living organisms, as well as stationary objects due to wavesdeparting from them. Therefore, in muddy water and even in complete darkness, the fish are perfectly oriented and do not stumble upon underwater objects. In addition to the lateral line organ, fish have sensory organs located on the head. In front of the head is a mouth with which the fish captures food and draws in the water necessary for breathing. Located above the mouthnostrils - the organ of smell, with the help of which the fish perceives the smells of substances dissolved in water. On the sides of the head are the eyes, rather large with a flat surface - the cornea. The lens is hidden behind it. Fish seeat close range and distinguish colors well. Ears are not visible on the surface of the fish's head, but this does not mean thatfish don't hear. They have an inner ear in their skull that allows them to hear sounds. Nearby is an organ of balance, thanks to which the fish feels the position of its body and does not roll over.