Features of fish reproduction presentation. river eel

Questions. 1. Name the main parts of the fish skeleton. What function do they perform? 2. What organs make up the musculoskeletal, respiratory, circulatory, and central nervous systems of fish? 3. List the characteristic features of the internal structure of fish. 3. Explain the importance of the swim bladder in the life of bony fish.

Reproductive organs. Fish are usually dioecious animals. The reproductive organs of females are the ovaries (see Fig. 119), in which eggs - eggs - mature. The reproductive organs of males are the testes (milt). Sperm mature in them. Fish are usually dioecious animals. The reproductive organs of females are the ovaries (see Fig. 119), in which eggs - eggs - mature. The reproductive organs of males are the testes (milt). Sperm mature in them.

Fish reproduction. Females spawn eggs into the water. Males pour seminal fluid containing sperm onto the eggs. After fertilization, that is, the fusion of a sperm with an egg, fish fry develop from the fertilized egg. Females spawn eggs into the water. Males pour seminal fluid containing sperm onto the eggs. After fertilization, that is, the fusion of a sperm with an egg, fish fry develop from the fertilized egg.

Fish reproduction. Most often, fish spawn eggs in the water and subsequently do not take care of the offspring. With this method of reproduction, there are a lot of eggs - hundreds, thousands, hundreds of thousands, even millions, since many of them die: some are eaten by predators. Most often, fish spawn eggs into the water and subsequently do not take care of the offspring. With this method of reproduction, there are a lot of eggs - hundreds, thousands, hundreds of thousands, even millions, since many of them die: some are eaten by predators,

Fish reproduction. However, among fish there are those who take care of their offspring. They lay eggs in depressions on the bottom (salmon), build nests (sticleback), carry eggs in their mouths (tilapia) (Fig. 122) or on their bodies (pipefish, seahorse). And there are also viviparous fish. Among cartilaginous fish, most sharks give birth to baby sharks. However, among fish there are those who take care of their offspring. They lay eggs in depressions on the bottom (salmon), build nests (sticleback), carry eggs in their mouths (tilapia) (Fig. 122) or on their bodies (pipefish, seahorse). And there are also viviparous fish. Among cartilaginous fish, most sharks give birth to baby sharks.

Fish reproduction. Of course, when caring for the offspring, the number of eggs laid by one female and cubs born is reduced to tens and units. In caring for offspring, complex forms of fish behavior are manifested. For example, a male stickleback jealously guards its nest from predators, and a tropical catfish, carrying eggs in its mouth, subsequently hides its offspring there if it is in danger. Of course, when caring for the offspring, the number of eggs laid by one female and cubs born is reduced to tens and units. In caring for offspring, complex forms of fish behavior are manifested. For example, a male stickleback jealously guards its nest from predators, and a tropical catfish, carrying eggs in its mouth, subsequently hides its offspring there if it is in danger.

Migrations. As you know, fish constantly move in the water alone and in groups. Many fish move long distances. Such movements of animals are called migrations. As you know, fish constantly move in the water alone and in groups. Many fish move long distances. Such movements of animals are called migrations. There are feeding migrations. Thus, herrings move in the ocean following the plankton that serves them as food, and sharks follow the herrings and hunt them. Migration associated with reproduction is interesting. There are feeding migrations. Thus, herrings move in the ocean following the plankton that serves them as food, and sharks follow the herrings and hunt them. Migration associated with reproduction is interesting.

Migrations. The fact is that places with abundant food are often not suitable for fish to reproduce, since eggs must be laid in clean water, rich in oxygen, heated by the sun's rays. The fact is that places with abundant food are often not suitable for fish to reproduce, since eggs must be laid in clean water, rich in oxygen, heated by the sun's rays.

Migrations. So the fish move, covering hundreds and even thousands of kilometers, from feeding grounds to spawning (reproduction) places. This is what salmon do in the Far East, northern Europe, or sturgeon in the Caspian Sea. For such migrations, these fish are called migratory. So the fish move, covering hundreds and even thousands of kilometers, from feeding grounds to spawning (reproduction) places. This is what salmon do in the Far East, northern Europe, or sturgeon in the Caspian Sea. For such migrations, these fish are called migratory.

Migrations. Adult individuals of Far Eastern pink salmon (Fig. 123) are doomed to death after spawning. Their instinct to leave behind offspring is so strong that on the way they do not eat anything and come to the spawning grounds exhausted from hunger strike, lay eggs, fertilize them and die. Adult individuals of the Far Eastern pink salmon (Fig. 123) are doomed to death after spawning. Their instinct to leave behind offspring is so strong that they do not eat anything on the way and come to the spawning grounds exhausted from hunger strike, lay eggs, fertilize them and die

Conclusions. Fish are dioecious animals. They reproduce in water: females lay eggs, males secrete seminal fluid onto the eggs. Most fish lay many eggs and leave them unattended after fertilization. Many eggs die. Fish that care for their offspring have few eggs, but most of them successfully develop into fry. Fish are dioecious animals. They reproduce in water: females lay eggs, males secrete seminal fluid onto the eggs. Most fish lay many eggs and leave them unattended after fertilization. Many eggs die. Fish that care for their offspring have few eggs, but most of them successfully develop into fry.

Subject:"Reproduction and development of fish."

The purpose of the lesson: show the features of reproduction and development of fish, reveal various forms of caring for offspring as an adaptation to the survival of the species.

Equipment: wet preparation “Development of fish”, table “internal structure of fish”, video film “Reproduction and development of fish”

During the classes

Teacher:

Zoology is interesting to study
It is useful for everyone to learn something new.
Children need to know a lot
After all, that’s why she’s precious about knowledge.

Indeed, zoology is a very fascinating science; in every lesson you discover the animal world anew.

You have already become acquainted with insects, mollusks, and fish. We will continue to study the latter.

Today our lesson is not quite ordinary, we are going fishing. The bite depends on the bait and the fishing location. Let's split up, some will prepare the bait, and others will place the fish.

Bait - individual task:

1. Write down the logical chain of structure of the digestive system of fish and prove that there is a relationship between its structure and functions.
2. What is the difference between the circulatory system of arthropods and vertebrates? What kind of blood - arterial or venous - enters the heart of fish?

(Two students complete individual tasks at the blackboard, the teacher divides the class into three groups, who will get to the top of the mountain faster.)

The one who solves the riddle will be the first to set off:

It doesn't fly, doesn't sing, but pecks.
(Fish)

Questions for the class:

1. Why can't a fish turn its head?
2. Name the 5 sections of the brain.
3. Name the organs of the excretory system of fish.
4. Name an animal that maintains a notochord throughout its life.
5. Name the sections of the skeleton.
6. Which part of the fish's brain is most well developed and why?
7. There's just a little bit left to the top. What internal organ systems did we remember?

(The teacher opens the systems on the board: SDS, excretory, nervous.)

Teacher: So, we found a place to fish. Look around! How beautiful it is, and there are a lot of fish. Is the bait ready? (Checking individual assignments.)

Teacher: Now all that’s left to do is catch a fish.

There is a pond in front of you. To catch a fish you need to answer a number of questions. Who will be the first to dare to cast a fishing rod?

1. Why is fish slippery and difficult to hold in your hands?
2. What is the meaning of the lateral line?
3. According to what physical formula do fish easily submerge in water and float to the surface?
4. Why are fish gills bright red? How can this knowledge be useful to you in practice?
5. What does the gill apparatus consist of?
6. Gills are an element of which system?

We repeated the respiratory system. (The teacher opens the respiratory system on the board.)

Teacher: caught fish, remembered the features of the internal and external structure, generalized knowledge about body systems. You currently know the central nervous system, excretory, nervous, digestive, and circulatory systems.

Today in the lesson we will get acquainted with the reproductive system, find out what organs are part of it, when and how the reproduction and development of fish occurs.

Lesson topic: “Reproduction and development of fish.”

Warning task: During the explanation, write down the organs of the reproductive system of fish in your notebook.

Teacher's story

The continuation of life of any living organism is based on the process of reproduction, i.e. reproducing one's own kind.

Most fish are dioecious animals, although there are also hermaphrodites among them (some sea bass and crucian carp).

The genital organs of bony fish are paired, located under the kidneys, on the sides of the swim bladder.

The reproductive organs of females are the ovaries, in which the reproductive gametes mature - eggs (eggs), which are released through the oviducts.

The reproductive organs of males are the testes, spermatozoa and biologically active substances mature in them, this liquid is called milk, and is excreted through the vas deferens. All these organs make up the reproductive system of fish.

So, based on the notes in your notebook, name the genital organs of females and males.

The time of onset of sexual maturity varies among different fish species. Using text No. 1 (Annex 1) handouts, name these age limits.

During reproduction, the appearance of fish changes. ( Rice. 164) What is this process called in biology? (Answer: sexual demorphism.)

The breeding season of fish, i.e. The spawning of reproductive products followed by fertilization is called spawning. Some species travel thousands of kilometers to their spawning grounds, a movement called migration.

Analyze a fragment of the film.

Explain:

A) why most salmon die during migration;
b) What does the term migratory fish mean?

The spawning site has been determined. Females of different species lay different amounts of eggs. For example, sunfish up to 300 million eggs, sea bass up to 1.5 million eggs, pike from 200 thousand to 1 million eggs, salmon from 2 to 14 thousand eggs, catfish up to 200 eggs. ( It is better to show an illustrated folding book.)

Despite the fact that the fish is an aquatic inhabitant, it can lay eggs not only in the water, but also in the most unexpected places. (Video “Reproduction and development of fish.”)

So, the eggs are laid out, the male pours milk on them. External fertilization occurs.

Caviar → ? → ? → Adult Fish.

What stages must a fertilized egg go through in order to turn into an adult fish? Using wet preparations for group work, write down the missing links in the logical chain in your notebook. (ABOUT student's answer: Caviar → Larva → Fry → Adult Fish.)

Compare the development of fish and insects. What are the similarities and what are the differences?
(Student answer: the development of fish is the same as that of insects with complete transformation.)

How does a fry differ from a larva? Find the answer in the handout ( text No. 2, Appendix 1).(Student answer: in nutrition.)

But not all fish are characterized by spawning; some are viviparous. Try to guess who it is:

I am an eternal wanderer and villain,
I don't sleep even for a minute
I click my teeth in the water,
I'm looking for prey here!
(Shark)

The shark takes pride of place in the gallery.

So, we got acquainted with the reproduction and development of fish.

Wherever you can find fish - in the seas, ponds, rivers. So Emelya from the Russian folk tale “At the Command of the Pike” once went to the river for water, scooped up a bucket, and there was a pike. Emelya contrived and grabbed her. Suddenly the pike says to him in a human voice: “Emelya, let me go into the water, to the little children, they are waiting for me - they won’t wait. And I’ll still be useful to you.”

I wonder if the pike told the truth? Can fish take care of their offspring? Scientists who have studied this problem say yes. Science knows of some species of fish that care for their young. During our conversation, fill out the table. (Appendix 2)

Tells about the behavior of stickleback... ( Student message.)

Try to figure out what other fish take care of their offspring.

There is no thread in it and there is no eyelet,
There are no fins among the abdomen;
Needle from year to year
Everything is sewing
Sea water.
She sews leisurely - what's the hurry?
After all, the sea still cannot be sewn together!
(Pipefish)

In the sea, in the thickets playfully
The flame of the fire curls -
The waters are blowing their mane
A restive skate.

He sees any hole,
Keeps a watchful eye on the prey,
Don't yawn, silly crustacean:
One jump from the enemy!
(Sea Horse)

They are also presented in our gallery, but the sea needles here are barely noticeable, once again proving the need for camouflage coloring. The eggs are brooded in a brood pouch on the belly.

But there are representatives who carry eggs in the stomach.

He lies at the bottom for hours
Moves his mustache in his sleep,
Under the driftwood under the bridge,
A mustachioed man lives in the river...
(Som)

The South American catfish carries eggs in the stomach; the bitterling, with the help of a long ovipositor, lays eggs in the mantle cavity of the mollusks.

Guys, let's find out if the amount of eggs laid and care for the offspring are related? Pay attention to the diagram. (Student answer: the number of eggs is inversely proportional to the care of the offspring.)

Thus, you have learned a lot about the reproduction and development of fish.

I propose, armed with knowledge, to go on a long journey - in the footsteps of the eel.

We need a captain who, using a map, will guide us along the eel's path.

We safely reached our destination.

What is the name of the path that we took after the eel? (Migration)

Why did the eel need to swim 5,000 km to the Sargasso Sea? (Spawning)

Define the concept of spawning.

What are the names of fish that go to spawn from rivers to seas and from seas to rivers? (Passing)

Name the representatives of passing fish.

Given that the eel spawns up to several million eggs, conclude whether it takes care of its offspring? (No)

So, during today’s lesson, we reviewed all the organ systems of fish, got acquainted with a new system - the reproductive system, found out the methods of fish reproduction, determined the stages of development and explained one of the reasons for migration.

Homework

1. § 33. Self-test. ( Appendix 4)
2. Creative message “Where and how can you apply knowledge about fish reproduction in practice.”
3. Which fish that live in the rivers of the Oryol region migrate, find out how, when and where they spawn.

Lesson topic: Reproduction and development of fish.

Lesson objectives: to show the features of reproduction and development of fish, to reveal various forms

Caring for offspring as an adaptation to the survival of the species

Develop the ability to analyze information,

Broaden the horizons of students and cultivate a caring attitude towards nature.

Lesson type: lesson on learning new material, combined

Method: problematic

Equipment: presentation “Reproduction and development of fish”

During the classes

Ι Org. moment

Hello everybody! The topic of our lesson is “Reproduction and development of fish.” Today you will get acquainted with the process of fish reproduction, the behavior of fish during spawning, ways of caring for the offspring of fish, we will analyze information and draw conclusions, and during the lesson you will expand your horizons and learn a lot of interesting things about fish.

II. Activation of cognitive activity.

Slide EEL

Among freshwater fish, the most amazing, both in appearance and in other features, is the river eel, a fish widely distributed in the rivers of Western Europe and the rivers of the Baltic Sea basin. At first impression, the eel looks like a snake. It has an elongated cylindrical body, reaching 1-1.5 m in females (males are smaller), and the entire rear half of this serpentine body falls on the tail, completely imperceptibly merging with the body and only laterally flattened at the end. The pectoral fins of the eel are small, there are no pelvic fins, and all paired fins are fused together and form one continuous fringe, which begins on the back, goes around the tail and continues on the ventral side to the anus. Eels swim quite briskly, bending their bodies like a snake and hunting for various small animals, and on occasion eating fish eggs.

Since ancient times, fishermen, and after them scientists, have noticed that in the rivers where eels live, one cannot find either eggs laid by eels or juveniles smaller than 20-25 cm. At the level of his era, Aristotle believed that eels develop from earthworms. The Russian ichthyologist L.P. Sabaneev heard an opinion about the spontaneous generation of eels from silt back in the 19th century from Narva fishermen. Suggestions have been made about the live birth of eels, although no one has seen pregnant females among them. And only at the turn of the ΧΙΧ and ΧΧ centuries the mystery was resolved.

Do you know the answer to this riddle?

III. Studying a new topic.

I think that we will find the answer to this riddle while studying our topic “Reproduction and development of fish.”

Fish are dioecious animals. In the body of females, in the ovaries, eggs develop. In the body of males, in the testes, sperm mature. The reproductive products of the fish are swept into the water, where fertilization occurs. Let's consider reproduction in river perch.

(presentation fragment of perch development)

Such fertilization occurring outside the female’s body is called external. Many fish have pronounced sexual dimorphism (when the female and the male differ in body shape, color, and size).

Slide Pink salmon and male before spawning

The appearance of the males changes beyond recognition: a hump forms on the back, large teeth appear on the jaws, the muzzle lengthens, and a large hook grows at the end of it. After spawning, adult individuals die, because while they were swimming to the spawning grounds they did not eat and were exhausted.

What do you think this is connected with?(search for a mating partner)

Slide Pike perch and pike perch

This is a well-known pike perch fish to all of us. The boys must have caught pike perch more than once. There is a legend among fishermen that pike perch are monogamous and form pairs long before spawning. From love, the color of the male acquires a blue tint. After spawning, the male takes care of the future offspring: he protects the eggs, moves his fins over them, saturating the water with oxygen and clearing it of silt.

The spawning of reproductive products by fish followed by fertilization of eggs, a special complex behavior during the breeding season is called spawning

The behavior of fish during the breeding season is instinctive, i.e. They are based on various unconditioned reflexes. Most fish lay eggs under strictly defined environmental conditions, specific to each species and much less variable than those under which fish usually live outside the breeding season. To lay eggs (spawn), fish gather in places with a certain temperature and depth of water, salinity, aeration, flow speed, mechanical composition of the soil, vegetation near the shore or at the bottom of the reservoir. All these factors are of great importance.

Developing eggs and larvae, especially in the early stages of development, are usually much more sensitive to environmental factors than adult individuals, therefore spawning at strictly defined values ​​of these factors contributes to their better survival.

Suitable places for spawning are called spawning ground . Pollution of the water and bottom leads to the impossibility of spawning or the death of fertilized eggs.

But in nature there are species of fish in which fertilization is internal and they lay not eggs, but large eggs containing a large amount of yolk and covered with a strong horny shell. Such an egg has the appearance of a quadrangular pillow, from the corners of which long twisted strands extend, with which the egg is secured to the algae and hangs until a relatively large baby hatches from it.

Slide Whale Shark Capsule

Slide Herring shark

Many sharks give birth to fully developed young

So, guys, what main ideas can be identified from the information you listened to?

1. Fish are dioecious animals.

2. Fertilization is external and occurs in water.

3. Sexual dimorphism is associated with living conditions, care of offspring, search

Mating partner.

4 During the breeding season, fish have complex behavior.

Fish migrations

As you know, fish constantly move in the water alone and in groups. Many fish move long distances. Such movements of animals are called migrations.

There are feed migration. So herrings move in the ocean following the plankton that serves them as food, and sharks follow the herrings and hunt them.

Migration associated with reproduction is interesting. The fact is that places with abundant food are not suitable for reproduction, because... eggs must be laid in clean water, rich in oxygen, heated by the sun's rays. So the fish move, covering hundreds and thousands of kilometers from their feeding grounds to their spawning grounds. Such fish are called passable

Semi-passable - (roach) from the Volga into branches in shallow waters.

Impassable - where they live and lay eggs.

Now please answer me why fishermen and scientists have not encountered their eggs in the rivers where eels live?

In 1922, scientists were able to determine the spawning sites of the eel. It turned out that eels ready to reproduce, having lived in the rivers for about 10 years, go to the Atlantic Ocean and do not return back. In the ocean, they make a long journey to the Sargasov Sea and spawn there at great depths. The larvae emerging from the eggs live in the open ocean for about 3 years and passively, carried away by the Gulf Stream, drift to the shores of Europe. Near the mouths of rivers, apparently under the influence of lower salinity of water, the larvae turn into small eels, and in this form they enter the rivers.

Almost all of our river fish go upstream to spawn and look for suitable places to breed; Such places - spawning grounds - are very diverse. Some need to lay eggs among plants (cyprinids), others look for deep and fast-flowing places in the riverbed itself (sterlet), others lay eggs among pebbles and stones in fast and shallow channels (salmonids).

Caring for offspring

Please look at the table. Analyze it, what kind of information is contained in the table?

The number of eggs laid by different fish varies. Why? What does this depend on?

This depends on how strongly the instinct of caring for offspring is developed in the species.

Caring for the offspring of some fish is limited only to the selection of a place for laying eggs. Then the laid eggs are left to the mercy of the fish, and only the extraordinary fertility of the fish saves their offspring from complete extermination. (Record-breaking Moon-fish)

Slide (moon fish)

There are, however, species in which care for the offspring goes a little further. To lay eggs, various species of salmon and trout dig holes at the bottom and then cover the fertilized eggs with sand or small pebbles. Thus, their caviar is exposed to less danger, and therefore the number of eggs is 2-8 thousand. Their eggs are larger and richer in nutrients (red chum salmon caviar)

In the table it was noted that the stickleback lays 100 eggs, the Aryan catfish - 3-10 eggs. How do they take care of their offspring? Does anyone know or your guess?

Slide Stickleback

An even more curious concern for the offspring is manifested in the stickleback. They do not leave their eggs to fate. Sticklebacks are very small fish, 4-9 cm, armed with sharp spines on their backs (a modification of the dorsal fin), which protect them from predators. The male builds a real nest from grass and algae, gluing it together with mucus, and then drives the female, ready to lay eggs, into it. Each female lays only a few eggs in the nest. A caring father not only crows the nest with eggs, but also refreshes the water in it, driving it into the nest with quick movements of his fins ( meaning?) , then for several more days it protects the fry that have hatched from the eggs until they are able to swim independently. Despite the fact that female sticklebacks lay 60-70 eggs, they develop in very large numbers, because they themselves have no commercial value and are not food for other animals (why? – needles)

Slide Tilapia and Aryan catfish

Tilapia fish hatch eggs in their mouths.

The Aryan catfish lives in the Atlantic Ocean, 30 cm, active at night when it hunts crabs, shrimp, and fish. They breed in the summer. When the eggs are laid, the male takes them into his mouth, where they incubate. During this period he cannot eat. The hatched fry remain close to their father, and in case of danger they hide in their father’s mouth.

Slide Siamese cockerel

Male Siamese bettas are bred in captivity for artificially organized fights. In the wild, males fight with rivals over territory. The male takes care of the offspring. he blows out air bubbles from which he builds a nest. Before fertilization, the male appears before the female in all its glory: fins spread out like a fan, shimmering with bright colors. Gill covers protruding in the form of a collar complement the image of a pompous dandy. Afterwards, he begins to build a nest, choosing for this a less illuminated area of ​​​​the water surface. When the male finishes construction, the fish begin to circle in a mating dance, which is accompanied by the release of eggs by the female and milk by the male. Fertilized eggs fall to the bottom, and the male hurries to collect them with his mouth, but does not eat them, but places them in the foam of the nest. On the second or third day, the larvae hatch from the eggs and hang in the foam with their tails down. The male takes care of them until they begin independent life.

Slide Seahorse.

Lives in the Black Sea. With their tail they cling to algae and in this position look out for prey - small crustaceans. They are protected from predators by a strong shell covered with hooks. The way they reproduce is interesting. The female attaches the eggs to the belly of the male, here the eggs are inseminated, and then a sac is formed around it from the overhanging fold of skin, in which the eggs are incubated until hatching.

And in conclusion, let us draw a conclusion.

They reproduce by viviparity, ovoviviparity, and in most cases they spawn

They have a developed instinct for caring for their offspring.

Consolidation.

1) explain the concepts: spawning, spawning ground, migratory fish.

2) What is migration and what is its role in the life of fish?

3) How does fish development occur?

Scheme Reproduction and development of fish

Crossword solution.

D/s: Prepare reports about fish.

Preview:

egg Males at this time emit milk. Motile sperm swim up to the eggs and sperm penetrate them

The fertilized egg begins to divide and a multicellular embryo is formed.

The embryo grows and soon leaves the egg shell, turning into a larva. The larva feeds and grows and becomes similar to an adult fish. She is called a fry. It grows relatively quickly: after about 2 months its body is 2 cm long, and after a year the young perch grows up to 10 cm.

Pink salmon sexual dimorphism (female and male)

The male pike perch turns blue from love

Whale shark egg capsule. Consists of keratin.

Viviparous herring shark

The larvae emerging from the eggs live in the open ocean for about 3 years and passively, carried away by the Gulf Stream, drift to the shores of Europe. Near the mouths of rivers, apparently under the influence of lower salinity of water, the larvae turn into small eels, and in this form they enter the rivers.

Sunfish up to 300 million eggs Eggs float freely in the thickness or on the surface of the water Cod, eel Sturgeon Pike perch, carp Perch Silver carp Catfish Pike 10 million eggs up to 1.5 million up to 1 million up to 900 thousand over 500 thousand Over 450 thousand over 200 thousand etc. Sticky eggs that are glued to plants or on the ground Chum salmon Pink salmon Stickleback Aryan catfish 3-4 thousand 1-2 thousand 100 eggs 10-3 eggs, etc. Caviar in holes filled with pebbles? ? Stingrays, sharks Single eggs in capsules Careful protection of offspring

The sunfish lays up to 300 million eggs and weighs about 700 kg

The three-spined stickleback's caring father not only does not leave the nest with eggs, but also refreshes the water in it.

Tilapia hatches eggs in its mouth

The Aryan catfish lives in the Atlantic Ocean. 30 cm. The male carries the eggs in his mouth. During this period he does not eat. In case of danger, the hatched fry hide in their father's mouth.

The male Siamese cockerel blows out air bubbles and builds a nest from them.

Seahorse eggs develop in a leathery fold on the male's abdomen.

2 N 3 E 4 R E 6 S 7 T 5 L U A P T U S H O K G O B U S H A K O N K O M I K I L I P I YA

Biology lesson with presentation. Reproduction and development of fish, grade 8.

2. Circulatory system of fish:
A) closed
B) open

3. Blood from fish brings to the organs:
A) nutrients
B) oxygen
B) nutrients and oxygen

2. Frontal survey.
List the digestive organs of fish.
What does the nervous system of fish consist of?
What organs belong to the circulatory system?
How do fish breathe?
What internal organ systems did we remember? Today in the lesson we will get acquainted with the reproductive system, find out what organs are part of it, when and how the reproduction and development of fish occurs.
III. Learning a new topic
In females, in the body cavity there is a large ovary in which egg cells (eggs) develop, in males - milk. Sperm mature in them. When the reproductive cells mature, the reproductive instinct appears in fish. His spawning Slide No. 3
Spawning- Complex instinctive behavior of fish during the breeding season. (Vocabulary work)
During spawning, fish instinctively look for places more favorable for the development of their offspring. Some species of fish rush from the sea to rivers, while others, on the contrary, leave rivers for the sea - these are the so-called migratory fish. Slide No. 4
They travel long distances to spawn. In the Far East, the movement of some salmon (chum salmon, pink salmon) during spawning presents an interesting spectacle: huge schools of fish move upstream, overcoming all obstacles. At rapids, fish jump out of the water, and in shallow places they literally crawl along the bottom, exposing their backs to the air. In the upper reaches of rivers, fish lay eggs and, completely exhausted, slide downstream. Many of them die in the process. Migratory fish that live permanently in the sea and enter rivers to reproduce also include sturgeon, salmon and some other fish. Slide No. 5
Eels, which have a long, serpentine body, live in fresh water bodies, and to reproduce they leave the rivers of Europe and North America to the Atlantic Ocean. Slide No. 6
This movement of fish is called migration. Writing in a notebook.
Many fish breed in the shallow waters of their reservoirs. Slide No. 7
We will study the reproduction and development of fish using the example of river perch. Perches, like most fish, are dioecious. Some time before spawning, the color of the perches becomes especially bright. They gather in flocks in creeks, oxbow lakes and other places that are shallow and without a current. Slide No. 8
The spawning process must be facilitated by certain conditions:
1. The water should warm up to 8-15 degrees Celsius
2. Absence of current at all or presence, but weak current.
3. The presence of aquatic vegetation, which makes these places ideal for fish spawning
4. Appropriate oxygen balance. Slide 9
Females spawn eggs glued together in the form of ribbons onto aquatic plants. Males emit milk at this time. Motile sperm swim up to the eggs and penetrate them. Slide No. 10
Development. Egg-----embryo-----larva-----fry-----adult fish
Writing in a notebook
Fizminutka Exercise to mobilize attention.
I.p. - standing, arms along the body.
1 - right hand on the belt, 2 - left hand on the belt,
3 - right hand on the shoulder, 4 - left hand on the shoulder,
5 – right hand up, 6 – left hand up,
7-8 - clapping hands above the head,
9 - put your left hand on your shoulder, 10 - put your right hand on your shoulder,
11 - left hand on the belt, 12 - right hand on the belt,
13-14 - clapping hands on thighs.
Repeat 4-6 times. Tempo - 1 time slow, 2-3 times - medium, 4-5 - fast, 6 - slow
The female lays more than 300,000 eggs.
-What is the reason for laying so many eggs? Perch eggs often die from drying out reservoirs, and larvae and fry die from enemies. Only due to the fact that during spawning a female perch spawns up to 300 thousand eggs, some of the offspring survive to adulthood. The number of eggs in fish of other species may be even greater. Than that of river perch. For example, cod hatches up to 10 million, sunfish up to 300 million. Those species of fish that are characterized by caring for their offspring. They usually lay a small number of eggs. But most of their eggs, larvae and fry do not die. For example, the male three-spined stickleback builds a muff-shaped nest from algae and guards the eggs laid in the nest by the females. With its spines spread out, the male will violently attack the fish. When approaching the nest, it cleans it of debris, repairs it, and with the movement of its pectoral fins drives fresh water there. For several days he guards the fry and does not allow them to disperse far from the nest, thus preserving the young offspring. Slide No. 11
The male seahorse does not build a nest, but carries the eggs in a special pouch on his belly. Slide No. 12
Even more amazing is the care for the offspring of the African freshwater fish tilapia: the male carries the eggs in the mouth, and even the fry hide in the father’s mouth in case of danger.
Slide No. 13
Among the fish there are also viviparous species. These include aquarium fish - guppies, swordtails, as well as some types of sharks and sea bass. Slide No. 14 In all viviparous fish, fertilization is internal; the embryo develops inside the female’s body. During this period, he can receive the necessary substances either directly from the mother’s body (as in some sharks), or from substances contained in the eggs (tooth carps). At the end of the development of the embryo, fry emerge from the female’s body and are capable of independent existence. As a rule, viviparous fish give birth to a small number of fry.
IV. Consolidation
1) Explain the concepts: spawning, migratory fish.
2) What is migration, and what is its role in the life of fish?
3) How does fish development occur? Slide No. 15
Conclusion: (students) So, during today’s lesson, we reviewed the organ systems of fish, got acquainted with a new system - the reproductive system, found out the methods of fish reproduction, determined the stages of development and explained one of the reasons for migration.
V. Homework pp. 77-79

Presentation on the topic: Reproduction and development of fish

Fill in the blanks in the text Fish are animals and have gonads. In males they are called milt, and in females -. The eggs mature in the ovaries, and the eggs mature in the testes. Fertilization in most fish. After fertilization, the egg develops and develops from it. dioecious testes ovaries eggs spermatozoa external larva fry

Several months Several months larva -> fry -> adult without fins" title="Stages of fish development in water several days in water several days Egg + sperm = embryo -> Several months Several months larva -> fry -> adult without fins" class="link_thumb"> 15 !} Stages of fish development in water several days in water several days Egg + sperm = embryo -> Several months Several months larva -> fry -> adult without fins Several months Several months larva -> fry -> adult without fins"> Several months Several months larva -> fry -> adult without fins"> Several months Several months larva -> fry -> adult without fins" title=" Stages of fish development in water several days in water several days Egg + sperm = embryo -> Several months Several months larva -> fry -> adult without fins"> title="Stages of fish development in water several days in water several days Egg + sperm = embryo -> Several months Several months larva -> fry -> adult without fins"> !}

Why do fish lay different numbers of eggs? What does this depend on? Moon fish300 million eggs Eggs float freely in the water Cod, eel10 million eggs Sticky eggs. which Pike, carp 1 million eggs are glued to the ground or Perch 900 thousand eggs to plants Chum salmon 3-4 thousand eggs Caviar in pits, Pink salmon 1-2 thousand eggs covered with pebbles Stickleback 100 eggs Catfish- 10-3 eggs

Choose the letter that corresponds to the correct answer and write it in order1. The egg of a fish is fertilization O 2. Testes are a shark D 3. Fusion of a sperm with an egg pink salmon T 4. Instinctive behavior of fish during the breeding season egg cell O 5. Movements of fish migration O 6. Viviparous stickleback fish E 7. A fish that builds a spawning nest 8. Salmon fish, which after spawning is doomed to death

Solving biological problems Most fish lay a huge number of eggs. Cod 7 million, pike 1 million. There are fish that lay hundreds or dozens of eggs. What kind of fish are these and how could they survive in nature? The freshwater fish bitterling lives in rivers where bivalves live. How can such a phenomenon be explained? Some species of fish travel thousands of kilometers from seas to rivers to their spawning grounds. At the same time, they lose a lot of weight and die after spawning. What makes chum salmon and pink salmon living in the Pacific Ocean go to spawn in small rivers on the coast of the Far East? Some fish species build nests during spawning, into which eggs are then placed. Males place fertilized eggs in nests, guard them, and return fallen larvae to nests. During this time they do not eat anything. However, as soon as the juveniles spread out and begin to live independently, the males are ready to eat them. How can such a phenomenon be explained?

Spawning, caring for offspring, external fertilization, dioecious animals, migration, migratory fish, ovaries, sperm, testes, eggs, sexual dimorphism Make up a logically connected story using terms (work in pairs). Determine the order of use of terms when compiling a story about the reproduction and development of fish.