CLASS CARTILAGE FISH. Cartilaginous sharks are a modern group of fish, including no more than 700 species of animals. Their skeleton remains cartilaginous for life. The skin is covered with a kind of scales, reminiscent in structure of teeth covered with enamel. There are no gill covers, like in bony fishes, and the gill slits open outwards with independent openings. The paired fins are located horizontally, the caudal fin has two unequal blades, of which the upper one is the larger one. The shoulder girdle of the limbs is represented by a solid cartilaginous arch, covering the body from the sides and below. There is no swim bladder. Representatives of the class are marine inhabitants: sharks and stingrays. Arctic shark
The largest - giant (up to 15 m) and whale (up to 20 m) feed on small planktonic organisms, filtering water through their gills; they pose no danger. Other sharks eat fish; often, accompanying ships, they pick up garbage. Giant shark CLASS CARTILAGE FISH. Sharks
In our country, in the Black and Sea of Japan, the dogfish shark (up to 1 m in length) is hunted. All sharks are marine inhabitants; only a few representatives enter fresh waters in the tropics. KATRAN (SEA DOG, SPY SHARK.
CLASS CARTILAGE FISH. Stingrays Stingrays do not look like sharks: their body is flattened in the dorsoventral direction. These are usually bottom-dwelling fish. Their gill slits have moved to the ventral side, so they take in water for breathing through splashes so as not to clog their gills with sand.
CLASS CARTILAGE FISH. Stingrays Stingrays feed on bottom organisms and fish. In many places they are hunted and considered very tasty. Stingrays have a long (about 35 cm) needle at the top of the tail base, often serrated, with a groove that secretes poison. Injections from tropical stingrays sometimes lead to death. A large, up to 2.5 m long, stingray (sea cat) lives in the Black Sea; there are stingrays also off the coast of Southern Primorye. In the tropics, in South and Central America, stingrays also live in rivers.
Electric stingrays have electrical organs on the sides of their bodies - modified muscles that generate a discharge of up to 220 V. With an electric shock, the stingray kills prey, usually small fish, and can stun the person who touches it. They live in warm waters, reaching the Mediterranean Sea. Electric stingray CLASS CARTILAGE FISH. Stingrays
Some stingrays have switched to living in the water column, feeding on small fish. These are eagle rays, mobulas and manta rays (sea devils). Manta rays are the largest rays, their body width reaches 7 m, and their weight is 2 tons. Manta ray
CLASS BONE FISH. SUBCLASS Ray-finned. Pikefish wikipedia Bony fish are characterized by the fact that their skeleton becomes partially or completely bony. This class includes a number of large groups of fish, distinguished by the characteristic organizational features already described above. Pike
SUBCLASS CARTILAGE-BONEY FISH This is a small ancient group of fish (including the well-known sturgeons - beluga, sturgeon, sterlet), which have a number of common organizational features with cartilaginous fish. Their tail fin, like that of sharks, is unequally bladed. The fins are arranged horizontally. Scales in the form of large bone plaques. The basis of the axial skeleton is the lifelong notochord, covered with a thick sheath. beluga
SUBCLASS LUNGPISHES Most of the skeleton in modern representatives remains cartilaginous throughout their lives; The notochord is preserved, and the spinal column is represented by the rudiments of the vertebrae. A characteristic feature of lungfishes is the presence, in addition to gills, of pulmonary respiration. One or two bladders that open on the abdominal side of the esophagus function as pulmonary respiratory organs. Lungfishes live in drying up reservoirs of Africa, Australia and South America. During the hot season of the year, they dig a hole at the bottom of the reservoir, climb into it and breathe atmospheric air until the water dries completely. After this, the animal forms a mud cocoon, becomes dehydrated, and hibernates. When water appears in the reservoir again, the fish “wakes up.” sporeclub.ru An ancient and unique group of freshwater fish.
SUBCLASS CLOSE-FISHES Loose-finned fishes are an ancient group of fish. The only species that has survived to this day, Latumeria, was found only in the Comoros area. These animals avoid illuminated areas. Lozenge-finned birds are predators; their mouths are armed with sharp teeth. Body length in adults reaches cm, weight kg. The vertebrae are rudimentary, and the notochord remains throughout life. The skull remains largely cartilaginous throughout life. The fins are fleshy, similar to blades, their skeleton has a general structural plan with the limbs of terrestrial vertebrates. 4. Coelacanth, or coelacanth. video.com.ua/index.php?showtopic=18448&pid=246609&mode=threaded&start=
Repeat the general characteristics and classification of the type Chordata.
Study the aromorphoses of the superclass Pisces. Write it down in your notebook.
Study the structure of fish. Complete the notes in your notebook.
Write down and learn the modern classification of fish.
Consider wet preparations of different types of fish.
Under a microscope, examine the two main types of scales of bony fish.
Study the external and internal structure of bony fish using the example of the River Perch (dissection of the fish).
In the album, complete 6 drawings, indicated in the printed manual, which are stored in the laboratory assistant department of biology and ecology, V (red tick). In the electronic manual, all the drawings necessary for drawing are presented at the end of the entire material.
In your notebook, draw and fill out Table 1:
Table 1. Distinctive features of fish organization
classes Cartilaginous fish and Bony fish
|
Class Cartilaginous fish |
Class Bony fish |
|
|
Ordinary representatives | ||
|
Features of the external structure | ||
|
Features of the internal structure | ||
|
Features of reproduction | ||
|
Ecological features |
In your notebook, draw and fill out Table 2:
Table 2. Variety of cartilaginous and bony fish
Know the answers to Control questions Topics:
General characteristics of the type Chordata.
Classification of the phylum Chordata.
Features of the organization of bony fish.
Systematic position, lifestyle, body structure, reproduction, significance in nature and for humans of the river perch.
Distinctive features of the organization of fish of the classes Cartilaginous fish and Bony fish.
General characteristics of fish In modern taxonomy of chordates Fish
(Pisces) are a superclass that includes two classes:
Phylum Chordata
Subphylum Vertebrata
Superclass Pisces
Class Cartilaginous fish (Chondrichthyes).
About 600 species. Class Bony fishes (Osteichthyes). More than 20 thousand species.Fish superclass(aromorphoses are major evolutionary changes leading to a general complication of the structure and organization of the organism):
1. Replacement of the chord with a cartilaginous, then bone spine.
2. Active search and capture of food (appearance of jaws).
3. Formation of the skull, which protects the brain.
4. The appearance of paired limbs - fins.
5. Developed brain and sense organs. The leading part of the brain is the midbrain (the so-called ichthyopsid type of brain).
6. Three semicircular canals appear in the inner ear, lying in mutually perpendicular planes, which ensures better coordination of movements.
7. One circle of blood circulation. The heart is two-chambered. There is venous blood in the heart. In lungfishes, the formation of a second, (pulmonary) circulation is planned.
8. Olfactory sacs are paired. Each of them opens outward with an independent nasal passage (paired nostrils).
9. Respiratory organs - gills.
10. The digestive tract is differentiated: the stomach is separated, the intestines are divided into thin and thick sections.
11. Differentiation of the digestive gland into the pancreas and liver.
12. Formation of trunk kidneys (the so-called mesonephric kidney).
13. Protective, mainly bone formations - scales - appear in the skin.
General characteristics of fish
Topic: “Class of bony fish. The diversity and significance of bony fishes"
The lesson was held in grade 7A, teacher - Gataullina R.I.
The purpose of the lesson:
Tasks: 1. Educational:
consolidate knowledge about the external and internal structure of fish
reveal the diversity of fish, the features of their adaptation to life in various conditions of the aquatic environment,
determine the importance of fish in nature and human economic activity,
basic measures for the protection of fish, to continue the formation of a scientific worldview based on the generalization of knowledge about the structural features of fish.
Educational:
work with the classification of the type of chordates,
learn to recognize studied fish,
be able to compare the structural features of fish,
be able to work with a textbook,
Educational:
show the influence of the environment and the functioning of fish organs on their structure,
reveal the relative nature of fitness,
show the human influence on fish numbers.
Equipment: tables, presentations, natural representatives of bony fish orders, drawings, envelopes with classification tasks.
Lesson type: lesson on systematization and assimilation of new knowledge with elements of methods for developing critical thinking
During the classes:
Epigraph for the lesson:
“Others got it from nature
Instinct is prophetically blind -
They smell it, hear the water...”
F.I. Tyutchev
1.Teacher’s opening speech (topic, purpose)
Hello guys. The topic of our lesson: “ Class bony fish. The diversity and significance of bony fishes", whose purpose is - systematize knowledge about the structure of bony fishes in connection with their habitat and identify the reasons for the diversity and importance of bony fishes.
Let's continue our acquaintance with the amazing world of fish-inhabitants of the water element, remember their structural features, way of life, learn about the great diversity and importance of fish in nature and for humans.
In people's minds, water is a fairy-tale element, where various fairy-tale creatures live, many of which are fish. For many peoples, fish is a symbol of abundance and fertility. In Japan and China, carp is a symbol of perseverance and courage, as carp is able to swim against the current. In Russian fairy tales we meet fish - pike, tench, bream, crucian carp. Pushkin's goldfish had a supernatural gift. In the Republic of Tatarstan, in the city of Tetyushi, there is a monument to the beluga, which was caught in 1921 in the Volga River.
Today we will take a trip to the kingdom of the goldfish, but in order to discover its secrets, we must remember the features of its structure, way of life, etc.
Repetition.
1.1. Let’s conduct a survey using the “CUIZ-CUIZ-TRADE” structure
1.2.Choose the correct judgments (self-test using the TIME-PEA-SEA structure)
1. All fish have a streamlined body shape.
2. The body of most fish is covered with scales. (+)
3. The skin of fish has glands that secrete mucus. (+)
4. There are fish that retain their notochord throughout their lives. (+)
5. The circulatory system of fish is not closed.
6. The heart of fish consists of two sections: the atrium and the ventricle. (+)
7. All fish have a swim bladder.
8. The excretory organs of fish are the kidneys. (+)
9. The body of a fish consists of three sections: head, body and tail. (+)
10. Pisces cannot turn their heads, but their eyes are mobile. (+)
11. Cold water has more dissolved oxygen than warm water, so the discharge of warm water (thermal pollution) can cause fish to die. (+)
When going to the kingdom of the Goldfish, you need to gain strength. Let’s plunge into the underwater world of a goldfish and imagine ourselves as any fish (using the “CONERS” structure).
Relaxation (30 seconds) (listen to the sound of the ocean and imagine themselves as some kind of fish). What kind of fish did you imagine yourself to be? (answers: shark, catfish, crucian carp, perch.)
2. Studying a new topic.
If you could imagine yourself with such a variety of fish, then most likely you already know many types of fish. Bony fish(lat. Osteichthyes) - a class of fish that have paired limbs (fins). The mouth of these fish is formed by grasping jaws with teeth, the gills are located on the gill arches with internal skeletal support, the nostrils are paired. They have a completely or partially ossified skeleton. As many as 96% of fish belong to this class. The body shape is very diverse: elongated, circular, torpedo-shaped, flattened, leaf-shaped, snake-shaped. Indeed, the class of bony fishes is very rich in its diversity, there are more than 36 orders, but today in the lesson we will get acquainted with 5 main orders.
Having repeated the classification, remembering the features of the external and internal structure, the lifestyle of bony fish, our main task at this stage is to find out how such a motley variety of fish was formed and what are they needed for? Let us display the goal and expected result of our work.
Sketch the skeleton of the fish: the head is our goal at this stage, the processes of the vertebrae are the orders and their features, and the tail is the conclusion or result.
Let’s imagine ourselves as participants in the “Young Ichthyologist” seminar. Your task: use material from the textbook, additional literature, natural objects of units, fill out a work card together with your group for the unit that you must characterize, draw the header of the table in a notebook to study other units at home. Work in groups (5 minutes). After the time has passed, we will hear one of the group representatives give a report on the table.
Exercise: Study the information, look at the pictures. Fill in the appropriate line in the table
Units
Living conditions
Features of the external structure
Representatives
Salmonidae
Herring
Carp-like,
Sturgeon
Perciformes
We summed up the results of the seminar.
Let's return to our goal: to identify the reason for the diversity of fish in nature. Each team cites a special feature that is characteristic only of representatives of the order they described (Herrings - a symmetrically laterally compressed body - allows maneuvering from predators and a silver-blue color; Perciformes - a characteristic feature is that their swim bladder loses connection with the intestines and exists independently, which allows them to swim quickly, moving calmly through the thickness, for example, in this order the swordfish, which reaches a speed of 120 km/h, a characteristic feature of salmonids is the presence of an adipose fin located on the dorsal side in front of the caudal fin, carp-shaped teeth absent, herbivorous, but there are pharyngeal teeth used for grinding food, sturgeon - flexible osteocartilaginous skeleton - great mobility, but there is external support - bone plaques, the long end of the caudal fin helps the fish stay on the bottom)
Let’s fill in the “fish bone” together and the conclusion: such a variety of fish is the result of living in different conditions, methods of obtaining food, i.e. adaptability to a specific habitat, which allows them to adapt to the aquatic environment as much as possible.
Conclusion: the diversity of living conditions determines the richness of this group in species and their extreme diversity.
But fitness is relative, if you change the conditions, for example, release a crucian crucian into the sea, where the water is salty, and it is adapted to fresh water, then its body will die, or any sturgeon is released into a stagnant body of water instead of a flowing one suitable for it, it will die. The saying “Where you were born is where you come in handy” fits here.
In order to understand the meaning of fish in the broad sense of the word, I asked Ksenia Polyakova to prepare in advance for the lesson on this topic (a story based on a presentation about the meaning of fish)
Let us highlight several important points in the meaning of fish in order to understand why it is necessary to protect and protect fish by filling out the diagram. Sketch the fish and use arrows to indicate the values. Demonstration of vitamin D (fish oil for normal calcium metabolism in the body of a growing child)
Now you know several orders of bony fish and their representatives. Remember what species of fish live, come to spawn, or their path runs along the Volga and what orders they are from?
Perch (perch-like), carp (carp-like), sprat (herring-like), sterlet (sturgeon), etc.
Well done! Many species of fish are found on the Volga, but how many of them were found here a few years ago? Even more, but consumerism and irrational attitudes towards fish have led to their reduction. You don’t have to look far for an example. I will show you two types of perch: one from the Volga River, and the other from a pond in one of the regions of our republic. What is their difference? (on the Volga specimen we see black formations, that is, the fish is sick with some kind of fungus or other disease) Reason: the water on the Volga River is polluted and its inhabitants suffer from this.
3. Fastening.
To consolidate what we have learned, we will create a “FREYER MODEL”, where the key concept will be bony fish (the model contains mandatory characteristics, optional characteristics, examples, counterexamples)
So we visited the goldfish and found out that not everything is in order in its kingdom, since man interferes in the life of the fish and often his activities are negative.
1. Fish are aquatic animals, the external and internal structure of which has maximally adapted them to life in the aquatic environment
2. All adaptations are the result of a long evolution of an animal with its environment
3. Mastering the aquatic habitat, the fish adapted to its various conditions (lighting, temperature, salinity, vegetation, density, etc.)
4. Over the long historical path of their development, together with other inhabitants of the water, fish have become an integral part of nature
5.Fish are widely used in human life as a source of vitamins, microelements, livestock feed, human food, etc.
6. Humanity must understand what a responsible role it has - to take care of the water resources of nature and its inhabitants
4. Results. Give ratings based on the number of fish.
5. Reflection.
Here are two fish, choose which one you like by raising your hands (one is smiling (the goal was achieved), sad (the goal of the lesson was not achieved).
5. Homework: read the paragraph, fill the table to the end, 3 people make a crossword puzzle
Biology lesson in 7th grade.
Topic: “Diversity of fish”
Target : show the diversity of fish, the features of their adaptation to life in a variety of aquatic environments. Determine the characteristics of the main classification groups of fish.
Cognitive aspect:
- to form initial knowledge of fish classification;
- determine the characteristic and general characteristics of the classes Cartilaginous and Bony fish.
Developmental aspect:
- developing the ability to independently find solutions to a given educational problem;
- development of search mental activity of students.
Educational aspect:
- fostering tolerance and respect for the opinions of others when working together in small groups;
- education for general biological culture.
Equipment: multimedia projector, screen, presentation
Lesson type: learning new material.
During the classes:
- Organizing time
I don't go. And I don't fly.
Try to catch up.
I can be golden
Well, look into a fairy tale!!
Who is this riddle about? (about fish)
Today we will continue our study of the Pisces Superclass.
Repetition of the studied material on the following questions:
- What body shape do fish have? Is it possible to determine at what depth a fish lives by the shape of a fish’s body?
- What is their body covered with? Why are scales called the passport and medical record of fish?
- Why do fish need fins?
- What do they need a swim bladder for? Do all fish have a swim bladder?
- What is a lateral line?
- Is the circulatory system closed or open? Do you have a heart? Which?
- How is the brain protected? Where is the spinal one located?
- Learning a new topic:
So, fish have all the characteristics of vertebrates. But if there are no more than 18 thousand species of mammals, birds, amphibians and reptiles taken together, then the number of fish species exceeds 22 thousand.
A problem arises – how not to get lost in such a variety of fish? Howdistinguish fish from each other? By what signs?
Fish are aquatic animals, their habitat conditions, food, and external features are different. Taking this into account, scientists have proposed a special taxonomy. What does the science of taxonomy study? What else do we need to study to learn more about fish?
Lesson topic.
The superclass of fish consists of two classes: cartilaginous and bony fish. Let's try to draw up a “Classification of Fish” diagram.
SUPERCLASS FISH | ||||||||
CLASS CARTILAGE FISH | CLASS BONE FISH | |||||||
Characteristic features: | SUBCLASS BONE | SUBCLASS OSEOCARTONGAL | SUBCLASS DIPNOI | SUBCLASS Lomonaceous |
||||
Representatives: Sharks, rays, mantles | ||||||||
- Fill out the table. Group work
task for group No. 1 Osteocartilaginous
2. Discuss in a group and highlight the characteristic features of osteochondral, or sturgeon, fish and find them in the proposed printed material.
task for group No. 2 Lungfish
2. Discuss in a group and highlight the characteristic features of lungfish and find them in the proposed printed material.
3. Write down the selected characteristics in the table.
4. Present your work at the board. Pay special attention and when answering, point out clearly visible external distinctive features.
task for group No. 3 Lobe-finned fish
2. Discuss in a group and highlight the characteristic features of lobe-finned fish and find them in the proposed printed material.
3. Paste the selected signs onto the sheet.
3. Write down the selected characteristics in the table.
4. Present your work at the board. Pay special attention and when answering, point out clearly visible external distinctive features.
task for group No. 4 Bony fish
2. Discuss in a group and highlight the characteristic features of Bony fish and find them in the proposed printed material.
3. Write down the selected characteristics in the table.
4. Present your work at the board. Pay special attention and when answering, point out clearly visible external distinctive features.
- Checking the table:
SUPERCLASS FISH | ||||||||
CLASS CARTILAGE FISH | CLASS BONE FISH | |||||||
Characteristic features: scales are placoid, have tooth-like projections, 5-7 pairs of gill slits, no gill covers, no swim bladder, cartilaginous skeleton, preserved throughout life | SUBCLASS OSEOCARTONGAL | SUBCLASS BONE | SUBCLASS DIPNOI | SUBCLASS Lomonaceous |
||||
There are gill covers, along the body there are 5 rows of large bone plates, with small ones between them. The skeleton - osteochondral. notochord - is preserved throughout life. There is a floating bubble | The scales are small, bony, the skeleton is bony, most have a swim bladder. | The bone scales are large and have lungs. Formed from the swim bladder, the notochord is preserved and the vertebral bodies do not develop. | The fins (especially the paired ones!!!) look like fleshy blades covered with scales. The skeleton is mainly cartilaginous, there is a notochord, the swim bladder is poorly developed |
|||||
Representatives: Sharks, rays, mantles | Representatives: sturgeon, beluga, sterlet, stellate sturgeon | Representatives: herring, sardines, chum salmon, pink salmon, roach, bream, carp | Representatives: australian cattail, | Representatives: Coelacanth |
||||
- IV. Fixing the material:(for the correct answer - 1 point)
Exercise No. 1 Find the extra ones in the row:
- Bream, gudgeon, roach, carp, sturgeon
- Herring , giant shark, manta ray, stingray.
- Herring, sardine, bream, shark .
Exercise No. 2 Choose the correct judgments:
1) in sharks and rays - a cartilaginous skeleton;
2) all cartilaginous fish breathe with gills covered by gill covers;
3) In lungfishes, the notochord remains throughout life. The vertebral bodies do not develop.
4) A representative of lungfish is the Australian cattail.
5) Coelacanth - a representative of Cartilaginous fish.
Reflection results:
rating “5” - 6 points
rating “4” - 5 points.
rating “3” - 4 points
V. Conclusions. Lesson summary.
Homework:
prepare a report and presentation on commercial fish
No one knows how many individual fish live on the globe. Another thing is individual species, i.e. groups, of organisms similar in appearance, internal structure, behavior and life activity, widespread in a certain area and capable of producing fertile offspring when crossed with each other.
All or almost all species of living fish are named and described in detail; experts count about 20 thousand species of fish - more than animals, birds, reptiles and amphibians combined. If we take into account fossil species, the diversity of fish will seem even more amazing.
Each type of fish, as well as all other animals and plants, received a Latin name consisting of two words, for example: - golden sea bass literally means “beautiful, magnificent”, hence the name of the city “Sevastopol”; “tappiz” means “sea”, hence “ultramarine”, “submarine”, “marinist”, the name “Marina”. So the Latin name can be translated as “beauty of the sea.”
It should be noted that folk names of plants or animals are sometimes double, for example, “brown hare” and “white hare”, “goshawk” and “sparrowhawk”. The Latin nomenclature allows specialists from all countries to accurately understand each other.
If scientists used only the popular names of fish, confusion would be inevitable. After all, even in one country, any widespread fish usually has several names. Thus, the fast predator of our large rivers is called “sheresper”, and “asp”, and “horse”, and “whiteness”. About 400 species of fish, bearing more than a thousand local names, are common in the country's inland waters.
In addition, many foreign, deep-sea or rare fish do not have popular names at all. When such fish begin to be caught, bred or kept in aquariums, they become familiar to wide circles and the Latin name is often used as a Russian word (Argentina, grenadier, blue whiting, notothenia, gambusia, platie, guppies, gourami, macropod, etc.).
It must be emphasized that both scientists and practitioners do not arbitrarily divide the world of plants or animals into any number of species. For example, species (as well as, for example, chemical elements) exist in reality, and not in human imagination. Species existed before the appearance of man on earth. Their reality is clearly visible from the following example.
On the island of New Guinea, scientists have described 138 species of birds. The native population recognizes 137 New Guinea birds. Consequently, with the exception of one controversial case, visiting naturalists and local hunters independently came to exactly the same conclusions regarding the diversity of birds on the island.
Unlike chemical elements, species on earth gradually replace each other, but so slowly that a correctly made description of them will not become outdated for many centuries. True, scientists often make amendments to the existing taxonomy, but not because species disappear or appear, but in order to eliminate previously made inaccuracies or in the event of the discovery of new species previously unknown to science.
Close, related species are grouped into genera. For example, fishermen distinguish several types of mullet: mullet, singil, sharpnose, and pilengas. These species are also recognized by scientific taxonomy. They all belong to the same genus.
Far Eastern salmon, similar in anatomy and lifestyle - chum salmon, pink salmon, sockeye salmon, chinook salmon, coho salmon and masu salmon - all belong to the same genus. Or, say, bream and bluegill.
In turn, related genera are reduced into families. For example, river perch, ruffe, pike perch are genera (each of them includes two species) belonging to the same perch family.
Families are grouped into orders, orders into classes, and classes into types.
Among vertebrate animals, the following classes are well known: mammals (or animals), birds, reptiles (reptiles), amphibians (amphibians).
And all other vertebrates - lampreys, sharks, stingrays, sturgeon, herring, flounder, etc. - are often classified by non-experts as fish. In fact, lampreys differ from fish (and all other vertebrates) in many fundamental features. Thus, lampreys have no jaws at all, and the mouth is a round sucker, lined with horny teeth along the edges.
The lamprey's skeleton consists of cartilage, the mucous skin is devoid of scales, there are no paired fins, the respiratory organs are sacs that open outwards with separate round holes, and inside are connected to a special tube lying under the esophagus.
But the fish themselves do not “fit” into one class. Most experts rightly believe that cartilaginous fish - sharks, rays, chimeras - are so unique that they constitute a special class.
The distinctive features of cartilaginous fish are as follows. The skeleton is completely cartilaginous, including the skull and jaws, which have a very simple structure: each consists of one large cartilage. The mouth is located on the underside of the head, quite far from the end of the snout, which is usually extended forward in the form of a sharp outgrowth.
The olfactory pits (“nostrils”) lie on the underside of the head, and not on the top, as in bony fishes. Gill slits, usually in the number of five pairs, are located on the sides of sharks, and on the ventral side of rays, and are not covered by gill covers; Chimeras have leathery gill covers. The skin of sharks is covered with numerous sharp teeth, while that of stingrays is bare or with large, scattered spines. All cartilaginous fish lack a swim bladder.
Many sharks are viviparous; the female gives birth to several dozen large young. Other sharks, rays and chimeras lay eggs that are protected by a strong shell and contain a lot of nutritious yolk.
Among bony fishes, the group of lungfishes is very interesting. Their main distinguishing feature is the presence of lungs located under the digestive tract, i.e., on the ventral side of the body (in other bony fish, the swim bladder, sometimes reminiscent of a lung in structure and function, lies above the digestive tract, i.e., closer to the back) . The “nostrils” of lungfish are connected to the oral cavity; This feature separates lungfishes from most bony fishes, but brings them closer to terrestrial vertebrates.
Lungfish differ from other fish in the structure of their scales, teeth, circulatory system, and brain. Several species of modern lungfish are common in Australia, Africa, and South America. These are rather large, sedentary inhabitants of stagnant, often drying up reservoirs, swimming and crawling among dense aquatic thickets. The paired fins of lungfishes resemble a herringbone or brush in their skeletal structure. This feature is shared with lungfish by the so-called lobe-finned fish, which are generally very similar in many respects.
Coelacanths were considered completely extinct, but in 1938, a living representative of this group, a coelacanth, was caught off the coast of Africa. Then we managed to find several more copies. The fascinating story of their capture and study is outlined by the famous ichthyologist J. Smith in the book “Old Quadruped”.
All other bony fish are included in the ray-finned class. The rays of their pectoral fin diverge radially (fan-shaped) from the base approximately in the same way as slightly splayed fingers on a human hand. This type of pectoral fin structure provides the fish with high maneuverability and agility.
The vast majority of modern species, genera, families and orders belong to ray-finned fish. The main orders are sturgeon-like, herring-like, carp-like, mullet-like, perch-like, cod-like, and flounder-like.
The systematics and diversity of fish (and biological systematics in general) may seem unnecessarily complex and cumbersome. But without it it would be impossible to study, describe and identify species. In the modern system of fish, each species finds a justified, legitimized place - like a book in a library with an exemplary catalog or like a soldier in a military unit consisting of platoons, companies, battalions, regiments and divisions.
For example, in almost all seas there are small sharks with sharp spines in their dorsal fins. Its local names are katran, nokotnitsa, prickly, dog; its Latin name indicates the genus and species. This shark belongs to a family that, together with several other families, belongs to an order belonging to the class of cartilaginous fishes, which also includes other sharks, rays and chimeras.
