Development of lesson annual cycle and the origin of amphibious. Annual Life Cycle Amphibians: Phenology, Daily and Seasonal Activity, Wintering

Frogs, Gametogenesis, fertilization and other seasonal events depend on numerous external factors. The life of almost all amphibians depends on the number of plants and insects in the pond, as well as air and water temperatures. Allocate different stages of development of frogs, including a larvae (egg - germ - a headastic - frog). Metamorphosis The tasty in an adult person is one of the most vivid transfigations in biology, as these changes prepare aquatic organism to land existence.

Frog development: Photo

In adversible amphibians, such as frogs and toads, metamorphic changes are pronounced most brightly, almost every organ exposed modifications. The body shape varies beyond recognition. After the appearance of the rear and forelimbs, the tail gradually disappears. The cartilage skull is a taller is replaced by a facial skull of a young frog. The horny teeth, which the headastic used for eating pond plants, disappear, mouth and jaws take a new form, the muscles of the tongue develop more stronger, so that it is more convenient to catch flies and other insects. The elongated thick intestine characteristic of herbivores is shortened to adapt to a carnivorous diet of an adult individual. At a certain stage of development of frogs, the gills disappear, and the lungs increase.

What happens immediately after fertilization?

Soon after, begins to move from one cell stage to another during the division. The first splitting begins from the animal pole and passes vertically down to the vegetative pole, separating the egg into two blastomer. The second cleavage occurs at right angles to the first, separating the egg on the 4 blastomer. The third groove is located at right angles to the first two, being closer to the animal than to the vegetative pole. It separates the four upper small pigmented sections from four lower. At this stage, the embryo has already 8 blastomers.

Further splits are becoming less regular. As a result, a unicellular egg gradually turns into a unicellular embryo, which at this stage is called Blastuly, which still at stage 8-16 cells begins to acquire spatial cavities filled with liquid. After a number of changes, one-layer blastuly turns into a two-layer embryo (gastrol). This complex process is called gastralization. The intermediate stages of the development of frogs at this stage imply the formation of three protective layers: ectoderms, mesoderms and entoderms, which are also known as the primary largers later from these three layers.

Golobastics (larvae stage)

The next after the embryo is a larva, which leaves the protective shell in 2 weeks after fertilization. After the so-called liberation of the larva, the frogs are called tadpoles, which are rather similar to small fish about 5-7 mm long. The body of the larva includes a distinct head, torso and tail. The role of the respiratory authorities play two pairs of small outdoor gills. Fully formed tadpole has organs adapted for swimming and respiration, light future frogs are developing from the pharynx.

Unique metamorphosis

Water headstuff undergo a number of changes that over time convert it to a frog. During the metamorphosis, some larval structures are reduced, and some change. Metamorphoses, initiated by the function of the thyroid gland, can be divided into three categories.

1. Changes in appearance. Rear limbs grow, joints develop, fingers appear. The forefinders, still hidden by special protective folds, come out. The tail decreases, its structures break and gradually it remains in its place. The eyes from the sides are moving to the top of the head and become scattered, the system of the side line of the organ disappears, the old skin is reset, and the new, with a large amount of skin glands, is developing. The horny jaws disappear along with larval skin, they are replaced with true jaws, first cartilage, and then bone. The RTA rupture increases significantly, allowing the frog to eat large insects.

2. Changes in internal anatomy. The gills begin to lose their meaning and disappear, the lungs are becoming more and more functional. The corresponding changes occur in the vascular system. Now the gills are gradually ceased to play a role in blood circulation, more blood begins to flow into the lungs. The heart becomes three-chamber. The transition from predominantly vegetable food to a purely carnivorous diet affects the length of the digestive channel. It is compressed and twisted. The mouth becomes wider, the jaws are developing, the language increases, the stomach and the liver are also becoming more. Perefros is replaced by mesosphere kidneys.

3. Changes in lifestyle. During the transition from the larva to the adult stage of development of frogs with the onset of metamorphosis, the lifestyle of the amphibian changes. It is more often rising to the surface to polish the air and inflate the lungs.

Frog - Miniature version of the adult frog

At the age of 12 weeks, the headastic has only a small tail residue and it resembles the reduced version of the adult individual, which by 16 week, usually completes the full growth cycle. The development and types of frogs are interconnected, some frogs that live at large altitudes or in cold places can live in the top stage all winter. Certain species can have their own unique stages of development that differ from traditional.

Life cycle frogs

Most frogs multiply in the rainy season, when the reservoirs are flooded with water. Tasps, whose nutrition differs from the meal of adults, can take advantage of the abundance of algae and vegetation in water. Eggs in a special protective jelly, the female lays under water or on plants located nearby, and sometimes does not even care about the offspring. Initially embryos absorb their yolk stocks. As soon as the embryo turned into a tasty, the jelly dissolves and the headasting comes out of its protective shell. The development of frogs from caviar in an adult person is accompanied by a number of complex changes (the appearance of the limbs, the reduction of the tail, the internal restructuring of the organs and so on). As a result, an adult person of an animal in its structure, lifestyle and habitat differs significantly from previous stages of development.

The answer was left the guest

1. The annual life cycle of amphibians
Annual life cycles in amphibians are well expressed in moderate latitudes with sharp seasonal changes in living conditions. With a decrease in the average daily temperature to + 12, + 8c, amphibians move to the places of wintering, and with further decrease in temperature in September - early October, they are hidden in shelters.
At the same time, individual individuals can move in search of wintering places for many hundreds of meters. The lake, pond and herbal frogs winter in reservoirs, gathering several dozen individuals together, hide under stones, among the aquatic plants, buried in il. They choose the deepest areas where the reservoirs are not freezing to the bottom. Toads, Gerlyanka, Tritons, Salamadras winter on land, climb into pit, rodent holes, hide in the trunk of rotting stumps, under stones, etc.
During the wintering period, amphibians are in stupor, they dramatically decreases metabolism, 2-3 times the reduction in oxygen, the number of respiratory movements and heart cuts.
2.Rugging a frog
Early spring, with the first rays of the warm sun, awakening from the winter hibernation of amphibians proceed to reproduction. During this period, males on the sides of the head develop paired bags - resonators that enhance sounds. The louder and melodious sounds published by the male, the more chances they have to conquer a girlfriend.
At the moment of reproduction, amphibians are divided into pairs. The female wipes large eggs, which are called caviar. The largest male produces a liquid containing spermatozoa on them. It means that the frog has an outer fertilization.
3. Developing frog
After a while, the shell of the iconic swells, turning into a puppy, transparent layer. There is a fertilized egg beneath it. Its upper side is dark, due to which heats up from the sun. Very often, lumps and tape caviar float to the surface of water, where the temperature is higher.
Development of pond frog
As in most amphibians occurs with metamorphosis. Also, like fish, the development of amphibians flows in water. The poet has no germinal shells formed. After about one one - two weeks from the cheeks, the larvae of frogs are published - thaws. Outwardly, they resemble fry fish. They have a long, flattened tail, as well as the side line. Blowing tadpoles with outer skin gills, which over time become internal.
In contrast to adult frogs, they have only one circle circulation, and in the heart is always venous blood. The first days of the life of the tadpole feed for seven yolk eggs, then they are squeezed with mouth, and they begin to eat on their own. Food serve a variety of algae, the simplest, as well as small water invertebrates

The influence of seasonal changes in nature on the life of amphibians. Annual life cycle is well expressed in amphibians living in moderate latitudes with sharp seasonal changes in living conditions.

At the beginning of autumn, with a decrease in the average daily temperatures up to +12 ... +8 ° C, amphibians move to the places of wintering, and with further decrease in temperature in September - early October they are hidden in asylums. In search of wintering places, individual individuals are moved to many hundreds of meters.

Ozerna, pond and herbal frogs winter in reservoirs, gathering several dozen individuals together, hide under stones, among aquatic plants, buried in il. They choose deep sections there, where the reservoirs are not freezing to the bottom.

Toads, Gerlyanka, Tritons, Salamandras winter on land: Close in pits, rodent holes, hide in the trunk of rotting stumps, under the stones. In a minor winter, when the Earth freezes to a greater depth, the amphibians wintering in it will die more than in water bodies, since the body temperature below -1 ° C is fatal for them. At small positive temperatures, winter amphibians are in a stupor: they dramatically decreases the metabolism, the number of respiratory movements and heart abbreviations decreases, the absorption of oxygen is reduced in two or three times.

In the spring, with the onset of heat, at the end of March and in April, amphibians are moving towards an active lifestyle, leave the places of wintering and are sent to the reproduction places. These spring movements are fairly friendly, animals overcome hundreds of meters, getting to small, well-heated by the sun of reservoirs.

After breeding, brown frogs, toads, quanks go to their usual summer habitats in the meadows, in the fields, gardens, gardens, etc. Tritons and Poles are carried out in the reservoirs for another 2-3 months, and then go to the land.

Reproduction of amphibians. Improvered amphibians in small, well-heated areas of water bodies. In the warm spring evenings, at the end of April and in May, loud piggy sounds are spread with ponds and rivers. These "concerts" arrange males frogs to attract females.

Proposition authorities in males of amphibians, like fish, serve semenniks, in females - ovaries. They are located in the body cavity, the reproduction time increases many times. Ripened eggs in the ovaries fall into oval. During the movement of the eggs, the eggs are covered with a transparent mucous membrane and through a clock is displayed out. In males, the seeds that have an oval shape, allocate many movable spermatozoa. Seed liquid rich in spermatozoa, in the seeds, falls into the clock and stand out out. Fertilization in amphibians outdoor. The bunches of fertilized caviar are attached to aqueous plants or separate lumps floating at the water surface. The ribbons of fertilized caviar of the toad, as well as separate triton eggs, are glued to the leaves of aqueous plants.

Development of amphibians. The development of a frog embryo (Fig. 137) in Ikrinka lasts about a half weeks. Then the embryo bursts the shell of the eggs, and the larvae comes out - a taddastic. In appearance and lifestyle, the tadpole is similar to the fish. He has gills, a two-chamber heart and one circle circulation circle, side line organs.

Fig. 137. Development of a frog: 1 - caviar; 2 - Exit Tallastries from Icrinka; 3.4 - tadpole with developed outdoor habies; 5 - Golovastic with inner harams; 6 - the appearance of the hind limbs; 7 - the appearance of the forelimbs; 8 - Cutting the tail; 9 - access to land

In the process of development, important changes occur in the headstand. The rear first develops, and then the forelimbs. Lungs appear, and the headstand is increasingly and more often rises to the surface of the water for breathing. In connection with the development of the lungs, the second circulation circle is formed, the heart becomes three-chamber. The tail gradually decreases. Golovastic becomes like an adult frog. Flooring from plant food moves to animal food consumption (becomes carnivorous) and leaves the reservoir. From the time of laying of caviar before turning the headstuffs in the frog passes 2-3 months.

Adult frogs have no tail. They begin to multiply aged 3-4 years.

The origin of amphibians. The reproduction of amphibians occurs just like in bone fish. Golobastics are more like fish than their adult parents. They have all the same organs that are needed by fish for life in water. All this testifies to the fact that amphibians occurred from some ancient bone fish.

It is known that some ancient bone fish used limbs (paired fins) for overwhelming from one reservoir to another. They have a primitive pulmonary bags that fish used for breathing with a lack of oxygen in water and while drying out water bodies. The greatest similarity exists between ancient amphibians, which appeared about 350 million years ago (Fig. 138), and the ancient freshwater cyzer fish - ripidists. These researches can be judged by the latimaria fish to be preserved so far (see Fig. 126).

Fig. 138. Ancient amphibian

It is important that the skeleton of pair fins of cyzer fish looks like a skeleton of the five-plated extremity of amphibians (Fig. 139).

Fig. 139. Skeletons of the front pair limb of the cyzerle fish (1) and ancient amphibian (2)

Apparently, it was from ancient ripidy that the first amphibians (mygiotheses) arose, on the external structure resembling modern tailed amphibians. They had limbs characteristic of terrestrial vertebrates, and well-developed belts of the limbs. A wide flexible head, widely divergent ends of the jaws made it possible to assume that the air was tightened into the lungs by lowering the bottom of the oral cavity. The hytioshyde has a typical fish feature: a skull with typical fish bones; residues (rudiments) of the gill lid; Long tail and side line organs.

It is assumed that primitive ancient amphibians led a water lifestyle, they fed and multiplied in water. However, they could go to dry and breathe air with a lack of oxygen in water, drying out the reservoirs. All this made it possible to call them four-legged fish. Ancient amphibians gave rise to modern triton, salamander, frogs, tobs.

Amphibians - separate animals that breed in water. Outdoor fertilization. Females sweep the caviar, males isolated seminal fluid. Development with the transformation: from the cheeky the casuals are similar from fish, which in the course of development turn into an adult amphibian. The lifestyle of amphibians changes depending on seasonal changes in habitat conditions. Amphibians occurred about 350 million years ago from the ancient cyzer fish ripidists. The first primitive amphibians retained many typically fish features. From them there were modern amphibians.

Exercises on the material passed

1. Describe the annual life cycle of the frog in moderate latitudes.
2. Name the similarities in the reproduction of amphibians and fish.
3. What is the similarity of tasty with fish? What confirms this?
4. What changes in the external and domestic structure occur from tasty in the development process?
5. Consider the main stages of the origin of modern amphibians.

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