Germ disc the accumulation of germinal cells on the animal pole of meroblastic eggs, having a mug. Gradually grieved at the edges, Z. The disk throws all the egg, and in the middle of the disk, the nucleus organs occurs, why Z. Disk, in contrast to a layer of flat cells (vitelocytes), is soon consisting of several cell layers.
Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron. - S.-PB.: Brockhauses-Efron. 1890-1907 .
Watch what is a "germ disk" in other dictionaries:
germ disc - Embryology of animals The embryonic disk - in mammals at the stage of gastruption, an orderly located cell mass remaining after the formation of the hypovest. Epiblast is formed from it ... General Embryology: Terminology Dictionary
Great Medical Dictionary
The same thing that Blastodysk ... Great Soviet Encyclopedia
- (Sin. Embrystick knot) Embubline at the rate of formation of the cavity of blastocysts before it is flattered into the embryonic disk (in the embryos of mammals and a person) ... Great Medical Dictionary
See germs ... Great Medical Dictionary
See germs ... Great Medical Dictionary
See germs ... Medical encyclopedia
- (Discus Embryonicus, LNE; Sin.: Blastodisk, discombustulus, germ shield, embryonic disc) Blastula, having a round plate, located in the area of \u200b\u200ban animal pole of the egg; peculiar to mollusks, shark and kostysty ... ... Medical encyclopedia
When describing the reproduction bodies, it has already been said that only yolk is formed in the ovary, which is an egg itself, while all other parts of the eggs are only its shells, gradually layering on the egg, as it is advanced after fertilization.
Egg structure. It is possible to directly familiarize yourself with the structure of the egg by opening a raw egg, complementing the picture that opens with the inspection of the longitudinal cut through the egg, welded by screwing, in which the protein and yolk solidified during cooking are retained.
To open the raw egg, it is necessary to put it horizontally and, clinging the tap of the scissors to the longitudinal line between the stupid and sharp end, carefully with the help of a tweezer, remove it in pieces until it turns out a sufficiently large "window". Next, in this window, remove suggestion shells and expose protein under them. Through the squirrel layer then will be shone in the center of the yolk ..
The yolk is separated from the protein with a thin film - the yellow shell (therefore, when the contents of the raw egg are produced in the pan in the manufacture of the scrambled eggs, the yolk falls in the form of a solid soft bag). On the side of the yolk, which is addressed to the top is small (about 3 mm in diameter), a light spot - a rings, or a germ disc; This is the place where the formation of the embryo begins.
Whatever s side of we put an egg, his germ disk will always be upwards: it depends on the fact that the opposite part of the yolk is much harder to the one where the germ disk is located, and with every position, the egg is always rotated down. What, however, supports yolk in the center of the egg, not allowing him to be pressed to the shell and not preventing his rotation around the horizontal axis?
If the internal contents of the egg are sufficiently naked from the shell and from the subsecuting shells, then it can be seen that the protein does not constitute a completely homogeneous mass. Around the yolk is more dense than under the shell, and from two opposite sides facing the stupid and acute ends of the egg, forms elastic twisted codes. These codes are the so-called grades or chalases - and hold the yolk in the middle of the eggs, without interfering with it at the same time turn around the axis (the chalase can be considered on the egg, pouring in a saucer).
Thanks to all these devices, the embryonic disk during the accident is always in the very advantageous position - it lies in the part of the yolk, which is currently closer to the body of the zeal, that is, to the heat source heating the egg.
The protein only fills the entire space between the yolk and the shell entirely on the fresh egg. As soon as the demolished egg cools, the protein in it is slightly compressed and in the dull end of the egg departs from the shell, fascinating and dressed his leathery film - an inner sheet of a two-layer suction shell; The other, the outer leaflet of the sublip shell remains tightly adjacent to the shell. Thus, on the stupid end of the egg between the two layers of the subseposition shell, an empty space is obtained, called an air chamber or a ombo. The longer the egg is, the more the protein swells due to the loss of water evaporated through the egg shell, and the air chamber increases it. Since the aircraft is clearly visible when the egg is viewed, it is easily able to determine the freshness of the eggs.
The solid shell of the egg, giving it a characteristic shape and enhancing it from damage during accidenting, consists mainly of calcium carbonate. For the formation of a chicken shell needs calcium salts, and it gets them together with food, walking small grains, found in the soil, particles of plaster, sink sinks, fragments of egg shell, etc. (eggshell should be given in finely angry Do not teach the bird to smear pending eggs). Fencing the egg from external damage, the shell should, however, be permeable for air (why?), And, considering the surface of the egg in the magnifier, you can see the many fine holes of the hastie small holes, or pores, become well visible after immersing the shell in diluted Colored ink). On the thick end of the egg (i.e., where the air chamber is formed) these holes are almost twice as much as on thin.
Egg chicken at the beginning of incubation
Although the shell is very fragile on a broken or exhausted egg and breaks even with a small nage, however, when it clothes the egg with a solid cover and it is not broken, the same shell is a very durable spherical arch capable of withstanding considerable pressure (try crushing the egg With an intact shell, squeezing it in a fist with all his strength). Therefore, the bird can sit on eggs, not crushing them (remember the leather sheath of eggs from the reptiles, who do not have to go off their offspring, and imagine what would have happened in the nest, if the bird shell had the same).
Only the demolished egg is covered on top of the shell still a thin film - a suprupny shell. This film passes through itself gases, but prevents the penetration of liquids and microbes into the egg. The suprautic shell is easily erased when washing and wiping eggs. Then the microbes easily penetrate through the pores of the shell and the egg is premature. It is necessary to strive to contain smoking rooms in purity so that the eggs do not need washing and wiping, then they will continue to remain in a fresh form longer.
Development of the embryo. The development of the embryo begins from the moment of fertilization of the egg - from the moment when the egg (yolk!) It comes out of the ovary and falls into the ovage. While the egg passes on the ovage and dresses with shells, (and it lasts hours of 15-20), a previously mentioned germ disk is formed in the yolk, so the egg demolished by chicken already concludes a germ that formed two layers of cells.
However, as soon as the egg was demolished and from the temperature of + 40 ° C to our usual temperature conditions, the development of the embryo is suspended, and in order for the egg to give chicken, it is necessary to put it under the zeal, i.e. again subjected to prolonged heating to + 40 ° C .
The old ideas that the embryonic disk of the egg at a conventional temperature (era of incubation) preserves vitality about 3-4 weeks - incorrect. A number of researchers have established that the storage of eggs is outside the conditions of incubation, both in artificial and in natural conditions, leads to the death of the embryos. Thus, when storing the eggs of home chickens for 20 days, the output was from 3.2, up to 25%, and for 25 days it fell to zero. The wildly ordinary gaga in the storage of eggs for 5 days, the death of the embryos fell to 40%, and within 8 days - up to 90%. In the sparrow birds, the storage of eggs outside the incubation for even a shorter time causes an even greater percentage of embryos death.
The zoom can be covered and warm up with its body about 15 eggs. Such a number of eggs and put under the zeal in the warm season. In the early conclusion of the chickens, when there is still little heat, it is recommended to put no more than a dozen eggs - otherwise the eggs lying around the edges will not fit the chicken body. In the first days of the development of the embryo, blood vessels begins to move away. On the 3rd day of reaching the embryo, it has some signs of lower vertebrates and is a coat of 6-7 mm in the form of a semicolon, lying left side on the surface of the yolk bag. At this time, the embryo is scheduled for several pairs of gill cracks, in which, however, there is no trace of the gills themselves and which in the future they will overeat. Only the first pair of gill cracks appeals subsequently in the auditory passage and in this form remains in an adult bird. The limbs at this time are represented only by the meetings.
On the 5th day, the embryo is already about 1 cm long and becomes clear when the egg is considered on the light of the lamp in a dark room. It is usually at this time and there is an inspection of eggs from under the ingredients, in order to separate the eggs remaining non-secretive (so-called fat) or for some reason have lost their vitality, from eggs with germs that will give chickens.
Until the 6th day of reaching, the future chicken is still no significant from the embryo of the reptile (lizard), which takes place the same level of development. The characteristic signs of the bird - the mouth of the beak, the presence of the neck, the differences between the first and second pair of limbs - are produced from him during the 6th and 7th day, when the embryo reaches a value of 16-17 mm, and on the 8th day Bird features become already quite clearly pronounced. Prior to this - on the 4th and 5th day of reaching - and the front and hind limbs at the embryo have the appearance of the paws, and the characteristic features of the birds are not noticeable on them - they are formed in the following days.
In the future, by the end of the second and during the third week of reaching, the embryo does not change its external form, but continues to grow at the expense of nutrient reserves available in the egg and gradually fills the entire inner cavity of the egg. The checker bag decreases, and finally, the last residues are closed inside the chicken body. By the end of the third week - on the 20th or on the 21st day - chicken exhibits the beak in the air chamber and inhales the air into the air, and then with the help of a solid tubercle on the top of the beak (find this "egg tooth" at chicken!) Out out of the egg.
During development in the egg, the embryo is not lighter, but through the so-called primary bladder or allantois. Allantois is formed from the rear of the intestine of the embryo, and the renal isolation; Then he processes around the embryo and the yolk bag, bearing to the subseposition shell. In the walls of Allantois, vessels, departing from the aorta, and through the pores of the shell makes the exchange of gases.
Chicken embryo at a later stage of incubation (14 mm size)
Incubation. The role of the zooms during the accidenting is reduced to the long and uniform heating of eggs to the temperature at which the embryo is developed; If we can easily maintain around the eggs the same permanent temperature in +39 or + 40 ° C, then we can do without the nasal. This is based on the use of incubators - devices of various devices, in the general features of the box, in which the desired temperature is artificially maintained. The source of heat for the indoor incubator can be - depending on the device of the incubator - either the electric current, heating the bottom and wall of the incubator, or in the tank of hot water.
In broad sizes, the withdrawal of chickens using incubators is used in large commodity farms. First, the use of incubators allows to remove chickens (for marketing them to the market) before the time when the chickens themselves are sitting on the eggs; In case of needing, with the help of incubators, all eggs obtained in the farm can be addressed to chickens, and finally the use of incubators makes it possible to use all chickens for egg socks (the chicken sitting on the eggs does not carry).
Now we have a thick poultry farm network, which contain several thousand nuclei chuckles, and the conclusion of the chickens is made exclusively by artificial incubation, and modern industrial incubators (various types) can be accommodated simultaneously to several tens of thousands of eggs.
The possibility of obtaining chickens without zepers by uniform heating eggs was known in China and in Egypt before the start of our era. In Europe, the invention of incubators already applies to a new time. Indoor type incubators appeared only at the end of the last century, and large incubators used on the poultry farms were first designed in the US in about 1915.
Chickens. Chickens leave eggs already dressed in yellow down and immediately become on their feet; From the first day of life, they can follow the mother and take their feed on their own. Such birds are called broods, in contrast to chicks, which from eggs are naked and helpless chicks (pigeons, crows, daws, etc.) appear from eggs. The chicken-zeper for a long time leads chickens, helps them, find food, protects against dangers and warms under the wing, as their own plumage is not enough to protect them from the cold (so chickens need to be protected from cold and dampness!).
When raising the chickens derived in the incubator, you have to arrange special heating in the form of boxes in which they have the ability to warm themselves as under the wings of the zeal. Such heels, or artificial uterus (brooms), like incubators, are heated by a reservoir filled with hot water, and in large farms - electric shock.
On the site of future contour feathers at the chickens in the first days of their life only small penets appear. From these primaries, feathers are rapidly developing (trace the order, in which they develop, - which groups earlier and what late!), And by the end of the fourth week, the chicken is covered with back feathers. After 6 weeks after the release of the egg chicken is already all dressed in feathers. From this age, his initial flying feathers are gradually starting to fall out, replacing new, which are somewhat different from their own form: the chicketer shutters are sharpening, and new, real fly feathers have rounded ends. Flying feathers are replaced in the correct sequence and fall around 2 weeks after another.
This gives us the possibility of flying feathers to determine the age of the younger chicken. The last chicken feather (at the very end of the wing) falls from a young bird when she will reach the age of six months. By 10 months (and at the early breeds before), young chickens and cocks achieve full maturity.
Literature: Yakhontov A. A. Zoology for Teacher: Chordovy / Ed. A. V. Mikheev. - 2nd ed. - M.: Enlightenment, 1985. - 448 p., Il.
Reproductive organs. In birds, as in other vertebrates, the breeding authorities serve in males - the seeds, in females - ovaries (see Fig. 165). They are in the body cavity. Boboven forms Paired Tsemenniki are located in the sacrum area. By the time of reproduction, their dimensions increase a thousand times. From the seeds, the seeds opened in Cloaca.
The females develop only one - left - ovary. It is located at the top of the left kidney. Reduction (the disappearance of the organ due to the loss of the function) of the right ovary is associated with the laying of large eggs covered with a rigid shell. Through a narrow pelvis, it is possible to promote only one egg.
Fig. 166. Egg structure: 1 - protein; 2 - yolk; 3 - air chamber; 4 - imprisonment shell; 5 - Halaza; 6 - shell
Egg development. Eggs in birds are large, rich in yolk. Ripened eggs falls into the ovage. In the upper part there is fertilization. The walls of the eggs are reduced, pushing the egg (fertilized egg) towards the clock. When moving, it is covered with egg shells, which are formed from the highlights of the glands of the eggs of the egg. Initially, the egg is covered with protein, then two fibrous (superal) and then shell shells.
The egg falls into a clock and postponed out. The formation of eggs in the eggs in birds of different species takes from 12 to 48 hours.
Eggs of birds are large, contain many nutrients and water in protein and yolk (Fig. 166). By the time of the laying of eggs on top of the yolk, a germ disk is noticeable - the result of crushing (division) of the fertilized egg. An yolk suspended on flagella - Halaza is located in the center of the egg. The lower part of the yolk is heavier, therefore, when the egg is turned over, the embryonic disk is always located on top, in the best conditions for heating when acted.
Outside the egg is protected by a limestone shell, in which there are numerous microscopic pores. Through them there is gas exchanges between developing germs and an external environment. The lime of the shell is partly used on the formation of a skeleton of a developing embryo. On top of the limestone shell, the egg has a thin nozzles, which protects it from penetration of microbes. Eggs shell at openly nesting birds has a protective color. The shell of the eggs of dumplogs and mornah is light or pure white.
Development of the embryo. The embryo in the egg develops very quickly at high temperatures (37-38 ° C) and a certain humidity. These conditions provide a bird based on the masonry. The auster regularly turns the eggs, changes the density of reaching: with an excessive high air temperature, the bird is raised in the nest, cools the masonry, periodically wasting the plumage, and protects it from sunlight his own shadow.
Fig. 167. Development of chicken: 1 - embryo; 2 - yolk; 3 - protein; 4 - air chamber; 5 - germ shells
The development of the embryo is well studied at homemade chicken (Fig. 167). On the second-third day, the chicken embryo is laid blood and nervous systems, eye bubbles are well noticeable. At the beginning of development, the forelimbs of the embryo are similar to the rear, there is a long tail, gummy gaps are noticeable in the cervical department. This suggests that the ancestors of the birds had a gills. On the fifth and sixth day, the embryo acquires bird features. By the end of the development of the chick, fills the entire inner cavity of the egg.
When hatching the chick, the chickness breaks up (parchment) shell, encourages the beak to the air chamber and begins to breathe. With the help of an egg tooth (a tubercle on the cluster), the chickpes chickpeas and selected from it.
Fig. 168. Paths of broken (1) and chicks (2) birds
Brood and nesting birds
Chickens, ducks, geese, swans of chicks hatch out eggs covered with thick octoch, with open eyes. After drying, in a few hours, they leave the nests and follow their parents. Birds with such type of development are called broods (Fig. 168, 1). Paths of brood birds are able to eat independently, but first need protection from enemies and heating by parents.
In pattering birds, pigeons, woodwood, parrots of chicks are hatched helplessly, with eyes closed. Their body is covered with rare poch or naked. They are helpless, need feeding, heating and protecting parents. Birds with such type of development are called chicks or nests. Parents feed such chicks for a long time in nests, they recover them after departure from the nest until young people acquire independence.
As a rule, nesting birds lay down fewer eggs than broods.
The laying of eggs and the care of parents for the offspring in the birds reached perfection, providing the same high efficiency of reproduction as the smallest lacking and fading with milk in mammals.
Exercises on the material passed
- Tell us about the features of the structure of bird breeding organs, noting the flight related features.
- What are the main stages of the formation of the egg before it is postponed?
- How does the chick of chick develop?
- What brood chicks differ from the nests? Give examples using Figure 168.
Equipment:
1. Each student (or on the desk): one raw and one boiled chicken egg, a cup of Petri (saucer), vacuine needle, magnifier, tweezers, watercolor paints, brush, scales with multiple, weak hydrochloric or acetic acid, test tube with gas trap tube, lime water in a cup, tripod.
2. For a demonstration, a 10% aqueous solution of chicken protein in a glass cup, an electric stove, a children's toy Vanka-stand, table (model) "Bird egg structure".
DURING THE CLASSES
1. Organizing time.
2. Activation of cognitive activity.
Setting a problematic issue. What appeared before - an egg or chicken?
Excursion in history.
Over the endless plain of the coal tribal period, the hot sun was shining ... under his incessant heat here and there they began to save the swamps, as if some unknown hand was expanding the sands ... Missed trouble emanating from the scorching sun and drying the swamps, forced amphibians to build another shell On eggs, protecting them from drying out ... And the one who thinks about the offspring thinks about the future ...
Approximately so, in a romantic-dramatic style, describes the occurrence of an egg with an additional shell by the author of the book "Long Way of Life" T. Jnikol. However, an egg with an additional shell is not amphibious, and reptiles.
In connection with what arose an additional shell on the egg? ( Climate change, need to protect against drying.)
What problems arose from the embryo in connection with the occurrence of a dense shell? ( The problem with breathing, metabolism.)
3. Setting the goals and objectives of the lesson.
Examine the structure of chicken egg as a spacecraft model.
4. Studying a new material.
The teacher invites students to discuss the problems of the cosmonaut, which is in a spacecraft in an near-earth orbit. Then proposes to hold a parallel between the cosmonaut and the developing embryo in the chicken egg. After discussion, a comparative table is recorded in the notebook.
comparison table
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Problem |
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cosmonaut |
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reliable Metal Ship Casing |
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food reserve or shipping by her ship from the ground |
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apparatus for water production or its stock |
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4. Air for breathing |
oxygen Development Apparatus or Live Plants |
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5. Waste: |
A) disposal; b) garbage containers |
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After that, the teacher proposes to study the structure of the chicken egg in order to fill the passes in the table.
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Questions, explanations and actions of the teacher Answers |
Conclusions and action of students |
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Determine the weight of the egg. Reference: the smallest egg is weighing 0.2 g, at the humming bumblebee. The most largest African ostrich is 1.6 kg. In extinct in the XV century. Related ostrums of Madagascar epiorons, the volume of eggs reached 8-10 liters. |
Weighed. Record weight in the notebook. |
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Shape egg |
Take the boiled egg. |
You need to tighten the egg on the table. Boiled spinning faster. |
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Consider its shape. Find stupid and sharp ends. In which literary work is described by war, which has been broken because of the various attitudes of people to the acute and stupid ends of the chicken egg? |
Sketch in a notebook appearance eggs. Ellipsoid form (rounded). "Travel Gullyer" Jonathan Swift. War of "Points" with "Tupuffes". |
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Why does an egg have a rounded form? |
After discussion, they come to the conclusion that the round the form gives the egg strength, which is important at the moment when the birds are based on eggs. 1. A boiled egg with force is compressed in hand (if the shell did not have cracks, it will endure compressions). 2. A textbook is put on the boiled egg (several textbooks). Knowing the weight of each book, determine the overall load that the egg shell is capable of withstanding. |
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Egg in Egg |
Why is an embryonic disc is always on the surface of the yolk? |
Open the egg using the prepar needle, expanding the hole to 1-2 cm. Pull the egg on the saucer so that the yolk is not rarely. Find the disk on the surface of the yolk. |
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As a tip, a children's toy Vanka-stand is demonstrated. |
The toy is weighted at the bottom, i.e. She is shifted by the center of gravity. So, the yolk is also displaced the center of gravity. |
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What is the importance of the embryo disc on the surface of the yolk? |
The embryo during the accident is located closer to the body body, where a more favorable temperature mode is created. |
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What egg structures make it possible to hold the yolk in the same position in the center of the egg? |
Find protein rods - chalases. It is found out that they hold the yolk in the center. |
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Clean the boiled egg, remove the yolk from it. Determine the shape, painting, sizes and weight of the yolk. |
Determine all the parameters and write this information to the notebook. |
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Spend on raw yolk preparation needle. What happened? What is covered with yolk outside? What function does this film perform? |
The yolk is covered outside the yolk shell, which gives the yolk shape. |
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What function does the yolk in the chicken egg perform? |
Yolk is a supply of nutrients for developing embryo. |
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Consider a protein of raw and boiled egg. |
Conduct observations. Raw - translucent, boiled - opaque, white (therefore - protein). |
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What is the protein function in the egg? |
Protein contains a stock of water. |
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Chemical composition of the shell |
To clarify the chemical composition of the shell, the teacher proposes to do the following experience: the shell pieces are placed in a tube with a solution of hydrochloric acid, closed with a plug with a gas-conductive tube. The end of the tube is placed in a cup with lime water. The teacher informs the class that the shell in birds is lime, consists of a substance close in composition to calcium carbonate, and proposes to record the reaction equation. |
Students observe the separation of gas bubbles from the shell. When the gas passes through the lime solution, the latter is purulent. Conclusion that carbon dioxide is distinguished from the shell. Record in the notebook Equation: |
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Pores in the shell |
Take into the hands of half the shell from the broken raw egg, carefully remove the film that lifts the shell from the inside, and set it aside until. |
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Look through the shell into light. What do you see? |
Consider the shell and conclude that the shell has pores located in groups. |
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In which part of the regulator pore more? What are the pores in the shell? |
Take the conclusion that the pores in the shell are needed for gas exchange. |
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Substormal shell |
Take a suction shell in the hands. Try to stretch it. Describe it. Why do I need this structure of the egg? |
Learn the object, describe, draw a conclusion: The subsepted shell serves as a filter for cleaning air penetrating into the egg. |
After studying the egg, the teacher invites students to fill the gaps in the comparative table composed at the beginning of the lesson.
The graph of paragraph 5 - "Waste" remains blank.
The teacher gives a brief explanation of the name of the chicken egg - amniotic. He reports that in the developing embryo, three germinal shells are formed - Amnion, Chorion and Allantois. The function of these shells is to provide independent development of the embryo in the egg. A developing embryo stores toxic substances (in particular, nitrogen exchange products) in Allantois. Now we can not observe Allantois in the egg, because the uncomfortable egg and the development of the embryo does not occur before us.
5. Conclusion. Conclusions by lesson.
1. Previously, the chicken appeared an egg - he was "presented" to the birds of reptiles.
2. The appearance of an amniotic egg was the most important step in the evolution of terrestrial animals, since it eliminated the dependence of the developing embryo from the presence of water and climate change.
3. A chicken egg can be compared with the spacecraft model, since it provides embryos with everything necessary: \u200b\u200bwater (protein), food (yolk), oxygen (pores in the shell) and at the same time removes or isolates the exchange products - carbon dioxide (pores in the shell), Urea (Allantois) and delays the penetration of bacteria (suction shell, film on the shell).
Attachment 1
In Dakar, the capital of Senegal, the building of the theater was designed, inside which there should not have been any column, none, even decorative, supports - the entire building should have been a huge, empty, thin reinforced concrete shell, based on a special foundation. When all calculations were completed, it turned out that the designed structure clearly lacks strength. Meanwhile, the natural egg shell, resembling the future of the theater building, withstood (in proportion to its size) appropriate loads. What is the matter? It was necessary to undergo a thorough study by an ordinary chicken egg. It was established that its strength is explained by a thin and elastic film-membrane, due to which the limestone shell is a pre-voltage design. This discovery, builders decided to take advantage of the structure of the theater building, only the membrane was, of course, was not made from the "chicken" material, but from the armotcement.
Appendix 2.
Spare protein contained in chicken egg yolk - viteline. This is phosphoproproteid, i.e. A complex protein containing phosphoric acid in its composition. In addition, the yolk contains iron, vitamins (especially many A, D, E). It is believed that the brighter the yolks are painted - the better the egg, since in this case the chicken has eaten naturally, namely green grass containing in addition to chlorophyll and pigments of the group of carotenoids. In the digestive tract, chruts chlorophyl is destroyed, and carotenoids, as more stable, ultimately accumulate in chicken yolk.
All minerals in chicken egg are in an easily digestible form.
1 - Halaza; 2 - shell; 3 - air chamber; 4 - outer suction shell; 5 - liquid protein; 6 - dense protein; 7 - germs; 8 - light yolk; 9 - Dark yolk.
Scheme of submicroscopic structure of chicken egg shell:
1 - Cuticula; 2 - outer layer; 3 - sponge layer; 4 - puffy layer; 5 - nipples; 6 - prompt film.
Appendix 3.
Chicken Egg - ovalbumin. This is a globular protein, each molecule which represents a compact ball laid in a certain way. While the ovalbumin is in the egg at room temperature, the molecules in the egg yolk are entangled like pasta. When the protein is knocked down or heated, the molecules are spread and begin to stronger each other stronger and become visible in aqueous solution, and the protein becomes tougher.
Literature
Lithinetsky I.B.Bionics: manual for teachers. - M.: Enlightenment, 1976.
Mikhailov K.E.What is an egg and how it lives // Biology, 1999, No. 3.
Nikolov T.Long path of life. - M.: Mir, 1986.
Skurikhin I.M., Nechaev A.P.All about food in terms of chemist. - M.: Higher School, 1991.
Walker J.Physical fireworks: (Questions and answers in physics). - M.: Mir, 1989.
The egg is protected from external influence by the shells or the oval shape shell, the combination of protein and yolk, of which the embryo or some animals are formed. We always see these components when we use eggs into food in any form. But there are other components, without which the birth of a new life is impossible. They can not always be noticed by the naked eye. And even if they are visible, we do not attach importance to them, since they absolutely do not affect the product.
Chemical composition of eggs
The whole egg without a shell contains:
- water - 74%;
- dry substances - 26%;
- proteins (proteins) - 12.7%;
- fats - 11.5%;
- carbohydrates - 0.7%;
Egg structure
All components in the structure of the eggs play an important role in the development of a new life. Yolk feeds the embryo, the air chamber is responsible for the delivery of oxygen, and the shell protects the future chick from the outside world. In more detail about the role of each component of the egg we will tell below. 
This is an external, the most firm, protective shell. It almost 95% consists of calcium carbonate. The main function is to protect the internal components from the negative effect of the external environment. When we clean the egg from the shell, it seems that it is smooth and solid. It is not like this: it is littered with microscopic pores through which air exchange and humidity adjustment occurs.
Important! If the shell is damaged in the process of sitting the egg, then the embryo dies.
The shell contains:
- water - 1.6%;
- dry substances - 98.4%;
- protein - 3.3%;
- ala (minerals) - 95.1%.
Substormal shell
The subseptee is a two-layer, consists of intertwined organic fibers. At the stage of formation of the egg, this shell sets its shape, and after it is formed by the shell. In the dull end of the egg, the layers of the shell are separated and the cavity filled with gas (oxygen) is formed between them.
Air chamber
The cavity filled with gas between the two layers of the suggestion shell - and there is an air chamber. It is formed when the chicken demolides the egg. It contains such an amount of oxygen, which is necessary to germin during the entire incubation period.
Did you know? Another name of the rope- Halaza. It comes from the Greek word "άάλαζα", which means "nodules".
Cord
This is a kind of umbilical cord, which fixes the yolk in a certain position (in the center of the protein). Located on both sides of the yolk. It is formed from 1 or 2 spiral tissue strips. Through the rope embryo is powered by yolk. 
Yellow shell
This is a transparent layer forms the egg itself at the stage of its development. Serves as a source of nutrients for the embryo in the first 2-3 days of incubation.
It is a totality of nutrients that accumulate in an animal egg in the form of grain or plates breathing sometimes into a single mass. If you carefully consider the crude yolk, then you can notice the alternation of dark and light layers. In the dark layers are mainly contained. In the first days of development, the embryo receives from the yolk not only nutrients, but also oxygen.
Yolk contains:
- water - 48.7%;
- dry substances - 51.3%;
- proteins - 16.6%;
- fats - 32.6%;
- carbohydrates - 1%;
- ala (minerals) - 1.1%.
In different places, protein density is different. The thinnest layer envelops yolks. In it and there is a rope. Next comes a thick layer of liquid protein, which is a power source for the embryo at the initial stage. The next layer is more dense. It feeds the embryo in the second stage and performs protective functions, not allowing the future chick to contact the shell.
Protein contains:
- water - 87.9%;
- dry substances - 12.1%;
- proteins - 10.57%;
- fats - 0.03%;
- carbohydrates - 0.9%;
- ash (mineral substances) - 0.6%;
- ovoalbumin - 69.7%;
- ovoglobulin - 6.7%;
- conalbumin - 9.5%;
- proteins-ovomukoids - 12.7%;
- ovomucins - 1.9%;
- lysozyme - 3%;
- vitamin B6 - 0.01 mg;
- flavin - 1.2 μg;
- riboflavin - 0.56 mg;
- niacin - 0.43 mg;
- pantothenic acid - 0.30 mg;
- biotin - 7 μg.
Germ disc
Another name is Blastodisk. It is a cluster of cytoplasm on the surface of the yolk. The birth of chicken begins with it. The density of the clock is less than the density of the whole yolk, which allows it to be all the time in the upper part (closer to the source of heat, no sleep).
