Fishes and their habitat. Fish habitats: life zones. Shallow water zone, or continental shelf

Lesson #32. Superclass Pisces. General characteristics, external structure L/R № 6 “External structure and features of fish movement”

Target: formation of students' ideas aboutfeatures external structure associated with living in water; the structure and functions of the limbs, the lateral line organs, the organs of hearing, and balance.

Activities:

Characterize features of the external structure of fish in connection with their habitat.
Master techniques for working with an animal identification guide.

Reveal fitness traits internal structure fish to live in water.
Observe and describe external structure and features of fish movement during laboratory work.

Textbook and notebook:

Konstantinov V.M.. Biology: 7th grade: a textbook for students of general education organizations/V.M. Konstantinov, V.G. Babenko, V.S. Kuchmenko. - M.: Ventana-Graf, 2014

Sumatokhin S.V. Biology: 7th grade: workbook for students of general education organizations / S.V. Sumatokhin. V.S. Kuchmenko. - M.: Ventana-Graf, 2015

During the classes

Checking the studied material ( Ind poll)

Give general characteristics phylum Chordata.

What are the structural features and life processes of the lancelet?

Appearance.

Length.

Origin of name.

The scientist who first described the lancelet.

Skin.

Skeleton.

Location and structure of the neural tube.

The structure of the digestive system.

Processes of nutrition and respiration.

Circulatory system.

Excretory organs.

Reproduction.

- Why is studying lancelet important?

- What is the complexity of the structure of chordates compared to invertebrates?

Learning new material

- Name the classes of Skulls. What do their structures have in common? ( Conversation on Fig. 106 page 136)

In adults, the notochord is replaced by the spine.

Nervous system: brain and spinal cord.

Well developed sense organs.

A special part of the skeleton, the skull, protects the brain.

Heart.

Kidneys.

Active lifestyle.

- (Formulation of the problem) We begin to study a special group of Cranials, the most numerous. It includes about 30 thousand. modern species. These Cranials are divided into two classes - Cartilaginous and Bony. The main criterion for this division is the substance of which the internal skeleton is composed - cartilage or bone.

- What is the name of this group of animals? (Fish)

Fish inhabit various bodies of water on our planet: oceans, seas, rivers, lakes, ponds. The aquatic environment is very vast: 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 led to the emergence of a wide variety of forms: the appearance of many adaptations to specific living conditions (Fig. 111).

- What structure of fish will we study today in class? (External)

And the topic of our lesson... (External structure of fish)

- Let's consider the features of fish adaptation to aquatic environment a habitat. Remember what features the aquatic environment has? (The slave himself with a textbook, natural objects, oral answers, diagrams in a notebook)

(Higher density than air; absence of sharp temperature fluctuations; mobility; low transparency; low oxygen content compared to air).

Laboratory work № 6.

External structure and features of fish movement.

Target. Study the external structure and methods of movement of fish.

Equipment: jar with fish in water, magnifying glass, glass slide, fish scales.

Progress

Examine the fish in a jar of water. Explain the significance of her body shape.

Consider the coloring of the fish's body on the ventral and dorsal sides. If it is different, indicate the reasons for these differences. (in fish, the belly is lighter than the back, from above the back to a certain extent merges with the dark background of the bottom, and from below the light belly is less noticeable against the light background of the water surface).

How are scales located on the body of a fish? What does this mean for the life of fish in water? Using a magnifying glass, examine the structure of an individual scale. (The outside of the fish body is covered with skin, which contains small (like perch) or large (like carp) bone scales. They overlap each other in a tiled manner and tightly cover the body and tail. The scales are constantly growing, and annual rings are formed on them, from which the age of the fish can be determined (Fig. 112, B, C). There are fish and bare-skinned ones without scales (for example, catfish). The scales are painted in silver-gray and black tones. Characteristic of many fish bright color, especially for those that live among coral reefs.

What does fish feel like? (it is slippery and covered with mucus).

Why do you think? . (The body of fish is slippery because it is covered with secretions from mucous glands located in the skin to reduce resistance during movement and protect against bacteria).

Find the parts of the fish's body: head, body, tail. Establish their boundaries (Fig. 112). Explain the importance of smooth transitions of body parts for the life of fish in water. ( streamlined body shape, without sharp transitions).

Find the fish's nostrils, eyes, and lateral line. What is the importance of these organs in the life of a fish? Find out what is special about the structure of the eyes.

Examine the fins of the fish. Which of them are paired, which are unpaired. Observe the action of the fins as the fish moves through the water.

1. Fins

   Unpaired

   Doubles

   Dorsal

   Caudal (serves as the main motor organ - with its help fish move forward)

   Anal

   Pectorals (participate in turning the body in the water, moving up, down and to the sides)

   Ventral (and unpaired ones hold the fish’s body in a normal, upright position)

   Sketch the fish in question. Label the parts of the body in the drawing. Draw a conclusion about the fish’s adaptability to life in water. Draw a picture of the fish's scales, noting the light and dark stripes. What is the age of the fish from which this scale was taken?

Adaptation of fish to the aquatic environment

Aquatic environmental factors

Adaptations to environmental factors

1

Density of water

Streamlined body shape, mucus, tiled arrangement of scales, fins.

2

Transparency

Protective painting; organs of vision - eyes.

3

Solutes, low oxygen content

Gill breathing, sense of smell.

4

Fluidity

Lateral line organs.

5

High pressure at depths

Change in body shape from spindle-shaped to ribbon-shaped and disk-shaped.

6

Strong absorption of sunlight

Various colors and luminous organs in deep-sea fish.

Behind the pelvic fins three openings are visible: anal, genital and urinary. Undigested food remains are expelled through the anus, and through the urinary harmful products vital activity, reproductive products are released through the sexual system: eggs in females and seminal fluid in males.

On the sides of the fish's body arelateral line organs - channels lying in the skin under the scales, at the bottom of which there are sensitive cells that perceive water vibrations. These organs allow the fish to perceive the flow of water flowing around the body and to distinguish objects thanks to the waves that emanate from these objects.

Other sense organs are located on the head. The border between the head and the body is considered to be the posterior edgegill covers (see Fig. 112, A). They cover the gills and constantly move, providing a flow of fresh, oxygen-rich water to the gills. The boundary between the body and tail is conventionally drawn at the level of the anus.

The mouth is visible on the front of the head. With its mouth, the fish grabs food and draws in water necessary for breathing. Located above the mouthnostrils , opening into the olfactory organs, with the help of which fish perceive the odors of substances dissolved in water.

The eyes of fish are quite large. The front side of the outer shell (cornea) is flat. Underneath it is a convex lens (lens), which gives a reduced image of objects on the retina, the cells that perceive light stimulation. Pisces see at close range (myopia) and distinguish colors.

The hearing organs are not visible on the surface of the head: they are located on the sides of the head inside the skull and are calledinner ear . The fish perceives sound waves in water over the entire surface of the body. Located next to the inner earorgan of balance , thanks to which the fish senses the position of its body, moving up and down.

CONCLUSION: Fish are well adapted to life in the aquatic environment. They have a streamlined body shape, fins that provide movement in the water, and sensory organs that allow them to navigate in the water.

Reinforcing the material learned . (Conversation)

By appearance determine the habitats of the fish shown in Figure 111.

Name the features of fish adaptation to life in water.

- Complete any of the sentences

I will always be... I won't... Today I realized... Today I thought...

D/z Paragraph 30, read, answer questions

The littoral zone is a place where there are almost no fish, since it is not yet a “full-fledged” body of water, but the border between the coast and the tidal zone. Therefore, only some fish risk entering the littoral zone. These include, in particular, the mudskipper, which stores water behind its cheeks and can get out even further than the littoral zone, climbing trees and intertwined roots. During high tide, jumpers often sit on tree branches, clinging tightly to them with their fused ventral fins. There are 10-12 species of these fish, which have a head resembling that of a hippopotamus, with bulging frog eyes.

They travel overland in search of earthworms and other living creatures - slider fish, oblong, reaching 15 cm in length. California gillicht gobies live without water in a damp, cool place for several days. Eels can crawl on the ground and outside the littoral zone, moving to other bodies of water if necessary. Some fish, for example, sphinx blennies, can sit in the littoral zone for a short time when thrown out by the tide, waiting for a new wave. Protoptera, lepidosirene and cattail, can live for some time without water in the littoral zone due to the presence of special lungs. Some polyfins can crawl out to the littoral zone and “travel” along it. Juvenile flag-tailed shorebirds prefer to stay in the pools formed by the tide. Only at the border of the littoral zone and the continental shelf is there constant water; there are small fish such as blennies, small catfish, greenfinches, needle fish, some coral fish, as well as lungfish and some cartilaginous ganoid fish.

Shallow water zone, or continental shelf

The shallow water zone, or continental shelf, is the habitat of important commercial fish: sturgeon, sprat, anchovy and many others. Herring, mackerel, tuna and other fish often come here during times of abundance of food. Among small fish temperate waters first place total mass occupied by anchovies, for which predators come: cod, sharks. In this zone, young fish of many species live their childhood. Grunion silverside fish, living in schools in the shallow waters of Mexico and California, breed in the littoral zone, burying their eggs in the sand at the water's edge during high tides. At low tide, the eggs develop in the warm, wet sand. In other species of silverside eggs, the eggs have thread-like appendages with which they are attached to some substrate.

They are found among fish of the continental shelf and sucker fish, in which the fused pelvic fins form a sucker, allowing them to cling to coastal stones even during strong excitement. Many fish that have no particular commercial value also live on the continental shelf: blennies, greenfinches, and cockerels.

In Australia, dangerous fish also live in the continental shelf zone: for example, sand and great white shark. Other sharks found in shallow water include the hammerhead shark, herring shark, and blue shark, but there are also harmless species like the leopard shark and catshark.

Coral Reefs: A Zone of Super-Rich Seas

Coral reefs are an area where all the brightest, strangest and funniest fish are gathered in one heap. Only on one Big barrier reef you can find one and a half thousand species of fish of the most diverse shapes and colors, from clownfish to ragpickers.

Formed Coral reefs many millions of years in small areas warm waters near the Antilles and Sunda Islands, not far from Australia, Africa, Madagascar, Sri Lanka. Tiny skeletons coral polyps gradually layered on top of each other to form coral islands.

The reef zone is home to many planktivorous and herbivorous fish, which attract many predators, and a large proportion of them are cartilaginous fish.

The entire community of animals and plants of coral reefs is divided into several environmental groups. Thus, parrot fish, whose teeth are very similar to an arched beak, which is extremely convenient for biting off pieces of coral and algae, are destructors, that is, destroyers of corals. Among other destructors it is widely known Starfish"crown of thorns"

Let's now talk about the simplest of all types of relationships between fish - predator-prey relationships. There are a lot of predators here on the reefs! This is especially true for sharks. The most common are the so-called reef sharks. There are sand sharks, white sharks, spiny sharks, and herring sharks. There is even a carpet shark, which, like scorpionfish and monkfish, flat and disguised by growths! "Sea Shadows" are always ready to grab a wounded or unwary fish. Of the stingrays there are stingrays, various electric ramps and sawfish. But next to these dangerous fish their harmless relatives, manta rays, swim (as discussed in Chapter 3, they can only harm a person if they accidentally fly into a boat).

There are also bony predators. These include barracudas, moray eels, scorpionfish, anglerfish, and groupers - there is no room to list them! They can send to better world most of their “neighbors” on the reef - except for larger fish.

I did not talk separately about the fauna of the bottom zone, since it is similar in fauna to the reef zone. However, there are also some interesting fish. For example, a common bug from the order Percopsidae. A curious way is how it buries itself in the sand: swimming head first near the bottom, it abruptly goes into reverse and, sticking its tail into the sand, quickly sinks completely into it, working with its fins. There are also many unusual species eels.

Fish are the largest group of vertebrates. It includes about 30 thousand modern species. Fish are divided into two classes - Cartilaginous fish (sharks, rays) and Bony fish (sturgeon, salmon, herring, crucian carp, perch, pike, etc.). The main criterion for this division is the substance of which the internal skeleton of fish consists - cartilage or bone.

Fish inhabit various bodies of water on our planet: oceans, seas, rivers, lakes, ponds. The aquatic environment is very vast: 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 water influenced the appearance of fish and led to the emergence of a wide variety of forms: the emergence of many adaptations to specific living conditions (Fig. 115).

Rice. 115. Fish of various ecological groups: 1.2 - tuna and cod living in the water column (pelagic): 3 - surface flying fish; 4 - bottom flounder

In fish, the laterally compressed body has a streamlined shape. In it you can distinguish the head, body and tail.

The outside of the fish’s body is covered with skin containing small (like perch) or large (like carp) bony scales. They overlap each other in a tiled manner and tightly cover the body and tail. The scales are constantly growing, and annual rings are formed on them, from which the age of the fish can be determined (Fig. 116, B, C). There are fish and bare-skinned ones without scales (for example, catfish). The body of fish is slippery, as it is covered with secretions of mucous glands located in the skin. The scales are painted in silver-gray and black tones. Many fish are characterized by bright colors, especially those that live among coral reefs.

Rice. 116. External structure of the fish: A - general plan of the structure: 1 - nostril; 2 - eye; 3 - mouth; 4 - gill cover; 5 - pectoral fin; 6 - ventral fins; 7 - dorsal fin; 8 - anus; 9 - anal fin; 10 - lateral line; 11 - caudal fin; B - scales with annual rings; B - determining the age of the fish

Fish have limbs - unpaired and paired fins. Unpaired are the dorsal, caudal and anal, or subcaudal. The most important of them is the tail one. It serves as the main motor organ - with its help fish move forward. Paired fins are located on the sides below: the anterior ones are pectoral, the rear ones are abdominal. The pectorals are more mobile, they are involved in turning the body in the water, moving up, down and to the sides. Pelvic and unpaired fins hold the fish's body in a normal, vertical position. Behind the pelvic fins three openings are visible: anal, genital and urinary. Undigested food remains are released through the anal, harmful waste products are released through the urinary, and reproductive products are released through the genitals: eggs in females and seminal fluid in males.

On the sides of the fish's body there are lateral line organs - channels lying in the skin under the scales, at the bottom of which there are sensitive cells that perceive water vibrations. These organs allow the fish to perceive the flow of water flowing around the body and to distinguish objects thanks to the waves that emanate from these objects.

Other sense organs are located on the head. The border between the head and the body is considered to be the posterior edge of the gill covers (see Fig. 116, A). They cover the gills and constantly move, providing a flow of fresh, oxygen-rich water to the gills. The boundary between the body and tail is conventionally drawn at the level of the anus.

The mouth is visible on the front of the head. With its mouth, the fish grabs food and draws in water necessary for breathing. Above the mouth there are nostrils that open into the olfactory organs, with the help of which the fish perceives the odors of substances dissolved in water. The eyes of fish are quite large. The front side of the outer shell (cornea) is flat. Underneath it is a convex lens (lens), which gives a reduced image of objects on the retina, the cells that perceive light stimulation. Pisces see at close range and distinguish colors.

The hearing organs are not visible on the surface of the head: they are located on the sides of the head inside the skull. The fish perceives sound waves in water over the entire surface of the body. These vibrations cause irritation of the nerve endings of the inner ear, and the resulting excitations are transmitted along the auditory nerves to the brain. Next to the inner ear there is an organ of balance, thanks to which the fish senses the position of its body, moving up and down.

Laboratory work No. 6

Subject. External structure and features of fish movement.

Target. Study the external structure and methods of movement of fish.

Equipment: jar with fish in water, magnifying glass, glass slide, fish scales.

Progress

1. Examine the fish in a jar of water. Explain the significance of her body shape.
2. Consider the coloring of the fish's body on the ventral and dorsal sides. If it is different, indicate the reasons for these differences.
3. How are scales located on the body of a fish? What does this mean for the life of fish in water? Using a magnifying glass, examine the structure of an individual scale.
4. Find the parts of the fish's body: head, body, tail. Set their boundaries. Explain the importance of smooth transitions of body parts for the life of fish in water.
5. Find the fish's nostrils, eyes, and lateral line. What is the importance of these organs in the life of a fish? Find out what is special about the structure of the eyes.
6. Examine the fins of the fish. Which of them are paired, which are unpaired. Observe the action of the fins as the fish moves through the water.
7. Sketch the fish in question. Label the parts of the body in the drawing. Draw a conclusion about the fish’s adaptability to life in water. Draw a picture of the fish's scales, noting the light and dark stripes. What is the age of the fish from which this scale was taken?

Fish are well adapted to life in the aquatic environment. They have a streamlined body shape, fins that provide movement in the water, and sensory organs that allow them to navigate in the water.

Exercises based on the material covered

1. By appearance, determine the habitats of the fish shown in Figure 115 (p. 10).
2. What structure do the body covers of fish have and what is their significance in the life of fish?
3. What sensory organs do fish use to navigate in the water?
4. Name the fins of the fish and describe their functions.

Fish are one of the most amazing aquatic animals. What features allowed them to adapt to life in these conditions? From our article you will learn about the external structure of fish and their diversity.

Habitat

It’s not for nothing that they say about confident people: “They feel like a fish in water.” These animals are not able to absorb oxygen from the air. Therefore, this environment is comfortable for them. The only exception is a small group of lungfish. They have both gills and lungs. The latter allow them to survive unfavorable periods of drying out water bodies and lack of oxygen.

Fish live in fresh and salt water. It depends on their type. Thus, gobies feel great even with an increase in salt concentration of 60%, and the carp dies.

Fish are adapted to different temperatures. This indicator is also individual. Californian lucania prefers to live in water with a temperature of + 50. And dalia, which lives in small streams in Chukotka, freezes and thaws along with the water.

Features of the external structure of fish

U cartilaginous fish gill covers and swim bladder are missing. The respiratory organs open outwards with independent openings. The skeleton of cartilaginous fish does not ossify. Ducts of the reproductive, digestive and excretory system open into one hole - the cloaca.

Sharks

The mere mention of these fish becomes scary. Indeed, most sharks lead a predatory lifestyle. Although whale giant shark, which are the most major representatives class, quite harmless. The basis of their diet is planktonic organisms.

The body of sharks has a streamlined shape. The caudal fin is of particular importance for movement. In most species it is variegated. It is also called heterocercal. In this case, the upper blade is much larger than the lower one.

There is a mouth on the elongated crescent-shaped head. It is surrounded by a large number of teeth arranged in several rows. As some of them are erased, with inside others grow up.

Is it true that sharks are fish without scales? It's not like that at all. Although at first glance her skin seems completely bare. Shark scales are called placoid scales. It is the most ancient in origin. In composition, shape and chemical structure, placoid scales resemble teeth. This is a plate with a spike protruding outward. Shark scales have a wide base and a flattened shape. The plates fit so tightly to each other that the skin appears bare. In fact, it protects the body of sharks like iron chain mail.

Placoid scales also perform additional functions. It significantly reduces water resistance, which allows sharks to reach speeds of up to 80 km/h. It also allows for virtually silent movements. This is very important during hunting and attack.

Stingrays

These fish have both a tail and scales. But their appearance is very unusual. Their body is flattened in the dorso-ventral direction. The pectoral fins of fish are fused to the head, resembling wings. It's about about stingrays.

Most of them live in the seas, but inhabitants of fresh water bodies are also known. Depending on their habitat, the color of stingrays varies from yellowish to black. The eyes are located on the upper side of the body. There are also sprinklers here. They represent the first pair of gill slits, which open the arches of the respiratory organs.

The characteristic body shape is interconnected with their bottom-dwelling lifestyle. Stingrays swim due to the wave-like movements of their wide pectoral fins. But they spend most of their time at the bottom. Here they bury themselves in the sand or wait for prey. The diet of these fish consists of small invertebrates, fish or plankton.

Bony fish

This class is much more numerous. Its representatives are more than 20 thousand species. They live in all types of reservoirs: from small rivers to ocean expanses.

These fish have more progressive structural features. These include the presence of a fully ossified skeleton and a swim bladder, which holds the body in the water column. The respiratory organs of bony fishes are protected by gill covers. The latter not only protect them, but also take part in the implementation of respiratory movements.

Fish without scales: is it possible?

The skin of fish contains numerous glands. They perform a protective function. The substances they secrete prevent the penetration of pathogenic microorganisms and reduce water friction during swimming. In some species, mucus contains toxic substances.

The body of bony fishes is also covered with scales, which are derivatives of the skin. It looks like translucent flat plates. The individual scales overlap each other like tiles. With its front edge, each plate goes deep into the skin, and the back one covers the scales of the next row. The growth of these structures is similar to the formation of tree rings. The growth of the plates occurs in the spring and stops in the winter.

Do all fish have scales? Absolutely. But in some it completely covers the body, while in others it is located on the body in separate rows. The latter traditionally includes cartilaginous fish and some bony fish. For example, beluga, sterlet, sturgeon and stellate sturgeon have sharp scales located along the body in several strands.

Features of covers

All features of the external structure of fish allow them to better adapt to life in the aquatic environment. Not only the speed of movement, but also the color of the integument allows them to hide from predators. In many fish it is protective. For example, the dorsal side of the perch is darker than the ventral side. This makes the fish less noticeable against the bottom. The belly of the perch is silver. This makes it invisible against the background of the water surface for prey, which is located below. Transverse stripes provide perch with excellent camouflage among algae thickets.

Other species have variegated and bright colors. It is called warning because its owners are almost always poisonous. Flounder has the ability to change its color depending on conditions environment.

What is the lateral line in fish?

A thin stripe is clearly visible to the naked eye on both sides of the body. It stretches from the gill slits to the base of the tail. This structure is called the lateral line. It consists of receptors called neuromasts. The latter are formed by a group of hair cells.

The lateral line in fish is the organ for sensing vibrations and movements in the environment. With its help, fish determine the direction and speed of the current. A similar structure is found in all larvae and some adult species of amphibians, cephalopods and crustaceans. Fish use it as a landmark in space, which is especially important during hunting.

Unusual species

Despite a large number of common features structures, there are a number of aquatic inhabitants that are in no way similar to representatives of this class. One of them is the blob fish. For most of her life, she has a normal appearance: tail, scales, fins... However, when she rises to the surface of the water, her body begins to swell and turn into a gelatinous creature, similar to a monster with a huge nose.

In the coral ocean reefs you can find body fish. It has the shape of a cube. To that unusual image you can add bright yellow with black dots. So far, scientists cannot explain why, during the process of evolutionary changes, the classic flat shape of the body changed to a cubic one.

Flat head with a vermiform appendage on which the eyes are located blue color, a huge mouth, bright stripes on the skin... Such an organism really exists. It's called frog fish. It was discovered in Indonesian waters not so long ago - in 2009.

And how can we not talk about the stargazer fish! You definitely won't confuse her with anyone. The Stargazer can be recognized by its two bulging eyes and wide mouth, which is located on top of its head. He burrows into the sand, tracking his prey. At first glance, this is an absolutely harmless fish. In fact, its spikes located above dorsal fins, contain toxic substances and are capable of generating small amounts of electric current.

So, the features of the external structure of fish that help them adapt to life in water include:

• Streamlined body shape. It consists of a head, body and tail. In benthic species that lead a sedentary lifestyle, the body is flattened in the dorsoventral direction.
• A large number of glands that secrete mucus.
• Scales that cover the body of a fish completely or form longitudinal stripes.
• In cartilaginous fish, the respiratory organs open outward through gill slits. In bones, they are closed with covers that protect the respiratory organs and are involved in respiratory movements.
• The presence of several types of fins: paired and unpaired. The first group includes abdominal and thoracic. The dorsal, caudal and anal are unpaired. They provide all types of movements, maneuverability and stable position in the water column.

Every self-respecting fisherman knows for sure that there is a huge diversity in the world of fish. In terms of their structure, these living creatures belong to chordates, but the types of fish range from small to large, from marine to river, and so on. In this article we will talk about what types of fish are, where they live and what is typical different types. We hope you find this information useful!

A little about fish

Fish are aquatic vertebrate gnathostomes that breathe through gills. They can live in almost any body of water: salty and fresh, from streams to oceans. As mentioned above, fish belong to the chordate type, since they have an internal skeleton along the axis, the so-called chord.

Waterfowl species worldwide numbered more than 34 million a few years ago. In science there is a special section devoted to the study of fish. It's called ichthyology.

Types of fish

As you know, types of fish are a huge section in ichthyology. Yes, of course, scientists spend a lot of time studying these animals. Pisces are classified as mentioned above, but each fish has its own characteristics.

Physiology and anatomy of fish

All creatures included in the phylum chordate fish are covered with skin and scales (not counting rare cases). The skin consists of two parts: the epidermis and the dermis. The epidermis produces a secretion that allows the skin to be protected. The dermis, the inner skin layer, plays a major role in the formation of scales.

Bony fish, unlike others, have various types scales. The types of fish, or more precisely, whether the fish belongs to one type or another, determine the characteristics of the scaly covering. So, sturgeons have ganoid scales. It is formed from bone plates coated with ganoin. The scales of bony fish living in our time are called elasmoid and are divided into round and serrated. The scales are arranged in such a way that the front plates overlap the rear ones. Not so long ago, scientists found that thanks to the comb surface of the jagged scales, waterfowl have increased hydrodynamic properties.

The coloration of fish has a huge range of colors; moreover, some colors are “warning”, which allows the body to be safe when near a predator. Also, colors can be pale, sandy, or sandy. It all depends on the habitat, the characteristics of the reservoirs. What types of fish, their environment, and colors.

The musculoskeletal system of a fish is its system of tissues and bones. It turns out that they previously had a third pair of gills, but then the organs evolved into jaws. Fish swim directly with the help of paired and unpaired fins. Moreover, thanks to their fins, they perform complex maneuvers.

The fins of bony aquatic animals have bony rays, while primitive ones have cartilaginous rays. Most fish use the caudal fin as their main propulsion mechanism. The spine in fish is formed thanks to individual unfused vertebrae. The process of swimming of fish occurs due to the contraction of muscles that are attached to the spine by tendons.

The musculature of fish has “slow” and “fast” muscles. They have a very developed sense of touch and smell, which helps them to perfectly navigate the environment where they are and avoid unfavorable places. Most chordates have a 2-chambered heart, a circulatory system, and a closed circulatory system. Blood circulates through the gills and body tissues from the heart.

Feeding in these living creatures occurs as follows: fish capture food, holding it with their teeth. Food from the mouth goes to the throat, then to the stomach, where it is processed by enzymes from the gastric juice. Fish have a wide choice of food. They can eat plankton, crumbs, worms, other fry, and some even large representatives of the class. But in general, fish are herbivores, predators and deritophages. What is most interesting is that many are able to change their type of nutrition, for example, at the beginning of life they eat earthworms and plankton, and in adulthood they feed on small or large representatives of the aquatic environment.

Fish have problems with pressure, for example, their pressure may be lower than the pressure of the environment, but due to the fact that these living creatures have a high urea content, this pressure is regulated.

Conclusion

Thus, we can conclude that the types of fish are very diverse, and each of them is characterized by a different structure, size, nutrition, and behavior. They are all different, and fishermen need to know everything about them before catching fish!