Features of the internal structure of amphibians, organ system table. Presentation on the topic "structure and activity of internal organs"

05.01.2015 5144 0

Lesson objectives:Ensure that students learn about the features internal structure and life activities of amphibians; lead students to understand the relationship between the structure of the organ system and the functions performed; improve the ability to work with a textbook, pictures, tables, diagrams, compare, generalize and draw conclusions.

Equipment:Wet preparation “Frog”, tables “Frog”, “Blood circulation patterns of vertebrates”, “Brain of vertebrates”, text “Getting food” (for each desk).

I. Organizational moment

I. Updating knowledge

1.Individual work using cards

Fill in the text with the necessary words instead of the gaps.

Amphibians are... animals whose life is connected with both... and.... On her head there are two bulging eyes, protected... . The frog breathes... air that enters its body through... . The skin of a frog, like that of all amphibians..., is always moist thanks to the liquid mucous secretions of the skin.... Amphibians with... body temperature. The respiratory organs are... and... . Frogs swim in the water. The frog swimming style is called breaststroke. One of the adaptations for swimming is... between the toes.

Compare the body shape of a frog with the body shape of a fish. What are the similarities and differences? Why can a frog live on land, but a fish that ends up on it dies?

How does a frog's skeleton compare to that of a fish? How can the appearance of these features be explained?

2.Solving biological problems.

1)In the temperate zone there are several dozen species of amphibians, and in the tropics there are about 1.5 thousand species. How can this be explained?

2)Why is the frog's skin covered not with water, but with mucus?

3)Green and brown, frogs have a protective body color, tree frogs change their color: on tree leaves they are green, on tree trunks they are brown. How can you explain that fire-bellied toads have brightly colored areas of skin?

4)There was a time when frogs (toads) were placed in vessels with milk and it did not turn sour for a long time. Explain this fact.

5)There is evidence that frogs deprived of cutaneous respiration live about 3-4 days, while frogs deprived of pulmonary respiration live 20-40 days. What conclusions can be drawn based on these data?

3.Quiet survey on the question “Features external structure amphibians in connection with living in two environments” (2 people).

4.Decipher the characteristics of amphibians shown in reference summary. Write a coherent story (see appendix).

I. Learning a new topic

1.Activation of cognitive activity.

A huge part of our knowledge of physiology is obtained from studies on frogs, unpretentious, patient, tenacious creatures. They also contributed to the development of embryology. It is no coincidence that there are monuments to frogs in Paris and Tokyo. These monuments were erected by doctors who conducted thousands of experiments on frogs.

Let's look at how the frog works inside and try to find out how the structural features of the systems internal organs associated with lifestyle.

-What internal organ systems ensure the vital functions of the animal’s body?

The digestive system of amphibians is in many ways similar to the digestive system of fish, having the same type of structure.

3 Consider the structure of the digestive system of a frog and note how it differs from the structure of the digestive system of fish. (§ 47, p. 142).

In addition, you need to take into account that frogs are the first “slobbers” on the planet. In order to easily swallow dry prey on land, a lubricant was required - saliva. Let me remind you that they feed on various invertebrates: ants, spiders, beetles, mollusks, etc. However, saliva does not contain digestive enzymes.

Interesting material about how amphibians get their food (independent acquaintance with the text).

Foraging for food

The frog's eyes are designed so that it can only see moving insects. Most tailless amphibian hunters rely on vision when hunting, but some rely on their nose as an assistant. Having smelled food, clawed and grass frogs, for example, begin to look for it with redoubled force.

But here is the prey in front of your nose. The frog, without hesitation, throws a lasso: its own fleshy tongue. It is attached to the frog inside out: not in the depths of the mouth, but not far from the chin. At its tip, in the middle, there is a deep notch, and it itself is covered with sticky mucus. The tongue jumps out of the mouth with lightning speed. It can reach prey sitting five centimeters from the frog. European cave salamanders have a long, stalked tongue with a clapper at the end. The Italian salamander throws out its tongue in just one fraction of a second, the aga toad leaves its mouth in three hundredths of a second, and the American toad almost twice as fast.

Frogs overtake prey anywhere: in front of them, above them, and can even jump up and fly backwards. They jump with their mouths open.

Not all amphibians use the lasso.

It seems that there is nothing easier than swallowing food: just have time to push it through with your tongue. However, this cannot be done by a frog's tongue. Who does this work? Eyes. From time to time they disappear from the frog’s face, are drawn somewhere inside the head and push another portion of food into the esophagus.

The prey enters the stomach entirely, untouched. The frog has about a hundred teeth, and about twenty more on the roof of the mouth. Don't be so quick to envy. These hundred teeth, every single one, on one jaw, on the upper one. They are directed inside the mouth. The teeth help the frog hold onto its prey, and that’s all. But this is also important. And since there is a need for teeth, when a tooth becomes old, it will fall out and be replaced by a new one. In older frogs, a second and sometimes a third row of replacement teeth can be found in the mouth.

Students formulate the main ideas. After independent work, summarizing the material about digestive system, the teacher notes the main thing:

1.The frog feeds on mobile invertebrates, which it catches with its sticky tongue; The eyes are involved in the act of swallowing.

2.Food in the oral cavity is moistened with saliva - this is an important adaptation for swallowing dry prey in dry conditions.

3.The intestines are differentiated; The duodenum (digestion of food), the small intestine (digestion and absorption), the large intestine (accumulates residues), the rectum and its extension - the cloaca - are noticeably distinguished in it. All this improves the process of food digestion.

What else can surprise a frog? Here's what.

Here sits a grass frog. Watch her for a whole hour - she won’t budge. And you can’t get rid of the feeling that the frog just finished a long-distance cross a second ago. Her throat vibrates so quickly. Up to 140 times per minute. What's the matter? Here's the thing. The frog does not have a chest. You ask: “What is the connection between the chest and the breathing process?” Straight. Let's try to breathe ourselves. Do you feel how your chest expands during inhalation, and how it returns to its place during exhalation? What does this mean? This suggests that the chest is involved in the processes of inhalation and exhalation. The muscles expand the chest cavity, the pressure in it drops - air rushes into the lungs. The chest cavity will contract, the pressure in it will become higher, and air will leave the lungs. This type of pump is called a suction pump. But frogs cannot use such a pump. How do they breathe?

Organized independent work based on material from § 47, fig. 201, chapter " Respiratory system" Students note the following:

1.The respiratory organs of amphibians are the lungs and skin. They breathe with their lungs only on land, and with their skin they breathe both in water and on land. Gas exchange occurs only through moist skin.

2.Amphibian larvae breathe through gills.

3.During the processes of inhalation and exhalation great value has a floor of the oral cavity that can move down and up.

4.The surface of the lungs is small.

The teacher supplements the students’ answers with the following facts:

1.The larger the oral cavity, the more air can fit into it. This is why the frog's flattened head is so wide.

2.The pump used by the frog to absorb air is called a pressure pump.

3.With a dual lifestyle, the frog has absolutely no need for first-class lungs. She is not in danger of dying from lack of oxygen.

To more actively use the new respiratory organ, amphibians acquired a second circle of blood circulation, and an additional partition appeared in the heart - it became three-chambered. The heart of amphibians has two atria and one ventricle. It is not separated by a septum and the two blood streams, arterial and venous, are partially mixed. The heart rate is 40-50 times per minute. The blood runs around her body in 7-11 seconds. The heart is designed in such a way that oxygen-poor blood flows to the lungs and skin; blood richer in oxygen flows to the body and internal organs. The most oxygen-rich blood flows to the brain.

Thus, despite the presence of only one ventricle, the frog has a system for the expedient distribution of blood, enriched in oxygen to varying degrees, between the lungs, internal organs and the brain (Teacher draws attention to the terms:veins, arteries, capillaries, venous blood, arterial blood).

Excretory system, like the respiratory system, is also closely connected with the circulatory system. In amphibians, as in all vertebrates, it consists of a pair of kidneys, ureters and a bladder. The blood brings liquid metabolic products to the kidneys. The resulting urine flows through the ureters into the cloaca, from there into the bladder, and then, after filling, into the cloaca and is removed out.

This is how the frog’s body works harmoniously. This work, which ensures the life of the animal, is under the control of the nervous system. As we see in Fig. 204, it consists of the central nervous system - the brain and spinal cord and the nerves extending from them. The brain has 5 sections: medulla oblongata, middle, cerebellum, intermediate, anterior. The head section of amphibians as a whole is small relative to the size of their body. The cerebellum is especially poorly developed, having the appearance of a small cushion.

-Why do you think?

However, the frog's forebrain is larger. The sense organs - the organs of vision, hearing, and smell - have received new qualitative development. The air environment provided great opportunities for orientation in space.

-Why does the frog feel so cold to the touch?

-Why are frogs, which are very voracious in hot weather? summer days, in winter, can they be kept for laboratory purposes somewhere in a closet or basement, without worrying about their food?

Conclusion:Amphibians are cold-blooded animals. Their body temperature depends on the ambient temperature.

II. Consolidation

ABOUTDescribe the characteristics of the internal structure and metabolism of amphibians in connection with their dual lifestyle.

О During the experiment, it was established that at a temperature of about 0 ° C frogs make jumps of 10-15 cm in length, and at a temperature of about 25 ° C - about 100 cm. Explain the results of the experiment.

Homework

§47, questions after the paragraph, notes in notebooks, terms.

Additional question.Prove that a three-chambered heart is indeed the most suitable for a frog given its amphibious lifestyle and the important role of cutaneous respiration.

Goal: to reveal the structural features and vital functions of internal organ systems in connection with the life of amphibians on land and in water.

Lesson progress

Work in the lesson takes place by first dividing students into 3 groups.

Motivational conversation.

What monuments do you know? What feelings arise when you pass by the monument? To whom are monuments usually erected?

There are frog monuments in Paris and Tokyo. (Presentation). Why were frogs awarded monuments?

Memory:

Warm-up: Fill in the missing words in the text.

Amphibians are:............ animals whose life is connected both with:............ and with:......... .................... On her head there are 2 bulging eyes, protected:................... ......... The frog breathes:...... air, which enters its body through:......... .......... The skin of a frog, like that of all amphibians:................................. ....., always moist, thanks to the liquid mucous secretions of the skin:....................... Amphibians have......... ........................ body temperature. The respiratory organs are:......................... and:................. ............. One of the adaptations for swimming are:................................. ....... between the toes.

Group assignments (oral response).

General characteristics of amphibians, their habitat

The external structure of the frog, a combination of terrestrial and aquatic features.

Skeleton and musculature of frogs.

Learning new material.

Outwardly a little disgusting, some are disgusted. There is a misconception that they cause warts on the skin. Their skin secretes mucus. Previously, in the old days, they were placed in a jar with milk, and the milk for a long time didn't turn sour. Frogs are the first slobberers. To be able to swallow dry prey on land, saliva was required. But this saliva did not contain enzymes. The frog's eyes are designed so that it can see moving insects. Having smelled food, they begin to search for it with renewed vigor. And if the prey is in front of their nose, then the frogs throw out their sticky tongue inside out. The tongue jumps out of the mouth with lightning speed. Frogs' eyes can disappear from their faces. They use their eyes to push food into the esophagus. But this is not at all why frogs were awarded monuments. And why, you will only find out by studying new material.

Independent study of the material (questions in groups) In 5 minutes we will listen to your messages.

Digestive and excretory system (compared to fish)

Respiratory and nervous system, comparative characteristics with the respiratory and nervous system of fish.

Circulatory system and metabolism (compared to fish).

When presenting messages, class students fill out the table:

Organ system

Features of the system structure

Functions

After presenting the messages, the material is summarized and the most important is highlighted (Presentation):

Food in the oral cavity is moistened with saliva - this is an important device for swallowing food on land.
The intestine is differentiated, it contains the duodenum, small intestine, large intestine, and rectum.
The frog's respiratory organs are the lungs and skin. It breathes with its lungs on land, and with its skin both in water and on land. Gas exchange only through wet skin.
Amphibian larvae breathe through gills
The surface of the lungs is small.
The heart has 2 atria and 1 ventricle. It is not divided by a septum and therefore the blood in the ventricle is mixed.
The excretory system, like the respiratory system, is also closely connected with the circulatory system. The excretory system is represented by a pair of kidneys, ureters and a bladder.
Nervous system consists of the brain, spinal cord and nerves. The brain has 5 sections: medulla oblongata, middle, cerebellum, intermediate, anterior. The cerebellum is especially poorly developed. The forebrain is large.
The organs of hearing, vision and smell are well developed.
Amphibians are cold-blooded animals. Their body temperature depends on the environment.

Maybe you can guess why the monument was erected? If not, you will learn about it at the end of the lesson.

Effective consolidation.

Distribute organs into systems:

Muscles
Cloaca
Heart
Lungs
Arteries and veins
Nerve
Spinal cord
Forelimb belt
Stomach
Intestines
Kidneys
Bladder
Hind limb belt
Scull
Brain
duodenum

Biological tasks:

Frogs move by jumping, why can't newts move by jumping?
Frogs are good swimmers, what features allow them to be such?
In frogs, 49% of oxygen comes through the lungs, how does 51% come?
The lungs of toads are better developed than the lungs of frogs, why?
Frogs can open and close their eyes. Why is this possible?
Frogs have a poorly developed cerebellum, what is the reason for this?

6. Unraveling the intrigue.

The monument to frogs was erected by doctors and physiologists. Thousands of experiments have been carried out on frogs. The vast majority of knowledge in physiology was obtained from studies on frogs, very unpretentious and patient creatures.

Summing up, grading.

Homework: paragraph 37. oral answers to questions after the paragraph.

Lesson type: combined.

Pedagogical technology: problem-based learning technology.

Assessment of the pedagogical situation: One of the leading forms of activity for 7th grade students is search activity. Therefore, in lessons for students of this age, the use of such cognitive methods as modeling, analogy, deriving consequences from facts and experiment is justified. These methods are based on the active activity of students. Subject this lesson allows, based on the independent work of students, to determine the content of basic educational units and formulate leading concepts. The search model was chosen as the learning model.

Target: create conditions for students to acquire knowledge about the peculiarities of the organization and operation of the internal organ systems of amphibians.

Tasks:

continue the formation of a system of ideas about the internal structure of vertebrates using the example of fish and amphibians;
create conditions for developing the ability to establish cause-and-effect relationships between the structure and functions of organs;
expand students’ understanding of the possibilities of the modeling method and thought experiment.

Methods: verbal - according to the nature of the predominant means speech activity, and logical - according to the method of obtaining educational information, based on logical operations, visual.

Equipment: media projector, demonstration tables, handouts, presentation.

Lesson progress

Today's lesson continues the study of chordates. The topic of the lesson is “Structure and operation of the internal organ systems of amphibians”,(start showing the presentation using a media projector)

Lesson objectives:

remember the internal structure of amphibians using the example of a frog,
learn to compare the structure of amphibians and fish,
construct a diagram showing the connection of organs in the frog’s body and the dependence of their structure and functions.

Why do you think it is necessary to know the structure of a frog? In what cases can this knowledge be useful in the future in adulthood? ( Suggested answer: for people who choose a profession related to the study of animals). It’s true, and a profession that requires knowledge of the structure and functioning of animal organs is, for example, a doctor, or rather a veterinarian.

Remember the children's poem by Korney Chukovsky about such a doctor? ( Suggested answer: Aibolit)

(Watching a video clip based on the cartoon “Aibolit” using a media projector – 2-3 min.)

Of course, in order to treat animals, you need to know how their body works. Can you imagine how much Aibolit probably knew about the structure and functioning of various animal organs! After all, he treated various animals. Remember who? ( Suggested answer: a fox that was bitten by a wasp, a watchdog whose nose was pecked by a chicken, hippos, ostriches, baby sharks, tiger cubs, camels, etc.)

Remember how Aibolit cured a bunny? ( Suggested answer: his legs were sewn on)

Look what wonderful legs Aibolit sewed on the bunny.

(Demonstration of a drawing of a bunny with human legs. Laughter.)

But is something wrong?…( Suggested answer: These are not bunny legs). Of course this is a joke. Doctor Aibolit should know well which legs to sew on and to whom.

But let’s imagine that a frog came to Aibolit for advice on whether it should exchange its heart for a fish’s, two-chambered one, since it still lives in water. Today let's try to imagine ourselves in the role of Doctor Aibolit, and give the frog sound advice.

So far we, perhaps, cannot solve the problem of whether to change the frog’s heart or not. And therefore I offer you several opinions. The correct ones may be the key to solving the problem.

Let's try to find them.

1. The main organ in any living organism, on which the work of other organs depends, is the intestine.

2. All organs in the body are connected by blood vessels.

3. Animals living in water do not need oxygen.

4. Blood transports substances.

5. The nervous system of vertebrates is represented by the ventral nerve cord.

6. The movement of blood through the vessels is ensured by the work of the heart.

(Correct judgments: 2, 4, 6)

How can correct judgments be connected with each other?( Suggested answer: you can build the following diagram)

Let's simplify the diagram. Its last part contains elements of one of critical systems organs, which one? ( Suggested answer: circulatory) And are functionally connected with this system ( Suggested answer: all other organ systems)

Correction of the original scheme.

The circulatory system is functionally connected to other organ systems. What are these systems? Let's remember their functions.

Working with a table - a guide

These systems are characteristic of fish and frogs. They perform the same functions in fish and amphibians.

But do you think the structure of these systems will be the same and why? ( Suggested answer: differs due to terrestrial lifestyle)

To understand the structure of the internal organs of a frog, we will use the text. Read the text and enter a “+” sign in one of the columns of the table on your handouts, after first comparing the structure of the organ systems of fish and frogs. Independent work of students using handouts.

Handout 1. Structure and activity of internal organ systems

Digestive system consists of the same organs as those of fish. The wide mouth leads into a large oral cavity. Placed at the bottom real language. It can be thrown out of the mouth and is used for catching small insects. Food moistened with saliva in the mouth passes through the esophagus and is exposed to digestive enzymes in the stomach. Next comes the duodenum (the initial part of the intestine). The ducts of the liver, gall bladder and pancreas open into it. The final digestion of food occurs in the small intestine. Nutrients are absorbed by the intestinal walls and distributed by the blood to all organs and tissues of the body. Undigested residues accumulate in the large intestine. Through the expansion of the cloaca, undigested food remains are removed to the outside.

Handout 2. Respiratory system

frogs breathe lungs and skin. Lungs are small elongated sacs with thin elastic walls. The role of a pump during breathing is performed by the oral cavity, the bottom of which sometimes falls and sometimes rises. Gas exchange occurs in the lungs: oxygen enters the capillaries and is distributed by the blood to all organs and tissues, and carbon dioxide is released from the capillaries into the lungs, which is delivered here by the blood from the organs and tissues. The lungs of amphibians are primitive: they have a small surface area of contact between capillaries and air. Therefore, the skin is important in gas exchange. Gas exchange occurs only through moist skin.

Handout 3. Circulatory system

The heart is three-chambered: two atria and one ventricle. Blood from the internal organs collects in large veins and enters the right atrium. The left atrium receives blood from the lungs and is rich in oxygen. When the atria contract, the blood passes into a single ventricle, where it is partially mixed. Mixed blood enters the aorta and is distributed to all organs and tissues of the body. Thus, amphibians have two circles of blood circulation: a small one, passing through the respiratory organs, and a large one, passing through other organs.

Handout 4. Nervous system

The nervous system consists of central and peripheral sections. The forebrain, divided into two hemispheres, is more developed. The diencephalon is almost hidden from above by the hemispheres. Moderately developed midbrain associated with vision. The cerebellum is poorly developed. This explains the monotonous movements and sedentary lifestyle.

(Demonstration of the completed summary table through a media projector. Self-test.)

Comparison of the internal structure of fish and amphibians

Organ system	Signs of a frog	Similarities with fish	Difference from fish
Digestive	The alimentary canal is differentiated (divided into sections).	+
	Available salivary glands and language.		+
	The intestine is lengthened due to an additional section.		+
Respiratory	When breathing, oxygen can enter the capillaries from water.	+
	Gas exchange occurs in the lungs and skin.		+
	Gas exchange occurs between atmospheric air and blood.		+
Blood	The circulatory system is closed, there is a heart.	+
Blood	The structure of the heart ensures the division of blood circulation into two circles.		+
	The nervous system includes the spinal cord, brain, and the nerves that arise from them.	+
	The forebrain is divided into two hemispheres.		+
	The cerebellum is poorly developed.		+

We see that the structure of the internal organs of amphibians has changed compared to fish; there are more differences than similarities. What could this be connected with? ( Suggested answer: transition to ground-air environment) Let's return to our diagram. In the diagram we see the functional dependence of the circulatory system and other organ systems. The transition to a land-air environment contributed to changes in all organ systems and primarily the respiratory system, and therefore the circulatory system- A frog's heart is not like a fish's.

Now our knowledge will be enough to model the frog’s body and understand the principle of organization of its heart in connection with the work performed in the body.

(Construction of a diagram on the board from individual elements, connecting them with each other. Accompanied by a story from the teacher.)

The structure of the amphibian heart allows the blood circulation to be functionally divided into two capillary networks. The first capillary network includes the skin and lungs. It saturates the blood with oxygen. The second capillary network includes all other organs. In it, the blood gives up oxygen, turning into venous. The three-chambered heart of a frog, in addition to its suction (pumping) function, performs a distribution function. Blood coming from the lungs (pulmonary circulation) enters the left atrium. Blood from muscles, internal organs and skin (systemic circulation) enters the right atrium. Further separation of blood flows in the heart is achieved physiologically, due to the work of a single ventricle. In the center of the ventricle the blood is partially mixed. When the ventricle contracts, blood is pushed into the arteries through the spiral valve. This valve sequentially opens the entrance first to the vessel going to the lungs and skin, then to the vessel going to other internal organs, and finally to the vessel going to the brain. This feature allows you to “sort” venous blood to the respiratory organs, and arterial blood to the brain.

That. Thanks to the structure and functioning of the heart, the frog has a system for the appropriate distribution of venous and arterial blood between the lungs, internal organs and the brain.

Let us now consider the question of a two-chamber heart. (Students do it independently.) ( Suggested answer: it will work if you remove the septum between the atria. In this case, venous and arterial blood will mix in the atrium. The same mixed blood will enter the lungs as the brain. Internal organs will receive less oxygen. The animal's activity will decrease).

What advice can we give to the frog? ( Suggested answer: the frog needs to preserve its three-chambered heart)

Let's summarize the lesson. Today in class we studied the structure of the internal organ systems of amphibians using the example of a frog, and compared its body with that of a fish.

At home, I suggest you try to simulate the system of working organs of a frog if it is under water. Think about how you need to change the constructed circuit.

Now let’s check how well you have learned the new material. Execute test task"Wave". If the sign refers to fish, then raise the “wave” above the horizontal line; if it refers to amphibians, then raise it below the line.

1. Occupy an aquatic habitat.

2. They have two circles of blood circulation.

3. The body is covered with moist skin.

4. Venous blood collects in the atrium.

5. Gas exchange occurs in one organ.

6. The intestines are supplied with mixed blood.

Check with comments.

Homework

1) No errors in operation:

Answer the question

The frog's forebrain is better developed than that of fish, which is associated with the behavior of the animal. Using your own observations and sources of additional information, prove this statement by comparing the behavior of fish and amphibians.

2) 1 or 2 errors:

Answer the questions

Can a frog spend its entire life in water without going onto land?

What advice can you give to a frog who wishes to have fish gills?

3) 3 or more errors:

Re-read the text on the handouts.

Try to recall what you read from memory and fill in the tables.