Stages of development of animals. The development of a frog from spawn to an individual in an unnatural habitat under different environmental conditions. The transformation of a tadpole

Frogs are the most famous tailless amphibians. Occupy an intermediate position between terrestrial and aquatic vertebrates.
The life of amphibians deserves attention, primarily because they occupy a special place in the history of the development of terrestrial vertebrates, being the first and most primitive inhabitants of the land. It is possible to assess the importance of amphibians in nature and human economic activity with further study of amphibians, whose biology has been developed only extremely superficially. The use of this animal for the study of biology gave recognition to the great merits of the frog in medicine.

Firstly, the lake frog is an exterminator of harmful animals. This representative of the amphibian order in its adult state feeds exclusively on animal food and, living in a wide variety of places, benefits by eating harmful insects. The importance of amphibians also increases because they eat insects with an unpleasant odor and taste, as well as insects with a protective color, in larger numbers than birds. Particularly noteworthy is the fact that land species of amphibians hunt at night, when the vast majority of insectivorous birds are sleeping.

Secondly, amphibian frogs are a food base for some fur-bearing animals. Frogs make up more than one third of all mink food - a valuable fur-bearing animal confined to water bodies. Willingly eats amphibians and otters. Relatively often amphibians are found in the stomachs of badgers and black polecats. Finally, many commercial fish in lakes and rivers in winter period in large quantities they eat frogs, which turn out to be quite affordable mass food.

Of course, there are also negative aspects when frogs exterminate juvenile fish in large quantities. Attracted by clusters of fry, numerous lake frogs turn out to be their main enemies here.

In some cases, frog tadpoles can compete with fish for food. Recently there have been indications of negative meaning amphibians in nature as guardians of dangerous infectious diseases such as tularemia.

Thirdly, amphibians are evaluated as laboratory animals. The ease of dissection of the frog, suitable size and vitality have made it a favorite test subject for a long time. Most of the instruments of experimental medicine and biology are designed for this animal. The technique of physiological experiment is constantly developed on the frog. A huge number of experiments and observations have been and are being carried out on these “martyrs of science”. Laboratories of large educational and scientific institutions consume tens of thousands of frogs a year. This expense may be so great that it is necessary to take measures so as not to destroy all the animals. So, in England, frogs are now under the protection of the law, and catching them is prohibited.

Thus, the question arises about the relevance of growing frogs in an artificial environment.

All this made it possible to determine the topic of scientific work.

Purpose of the study: find out under what different, artificially created conditions, the frog larva will go through all the stages of metamorphosis faster.

Research objectives:
1. Study the scientific literature on biology;
2. Identify the causes of positive and negative influences environment for development;
3. Conduct research work.

Object of study: caviar of an ordinary frog.

Hypothesis: Various environmental conditions affect the development of a frog from spawn to individual in an unnatural habitat. If you create all the necessary conditions, then you can achieve the maximum percentage of survival of tadpoles.

Reliability of results provided by the personal participation of the author in the research process.

lake frog

Description

The lake frog is a species of tailless amphibians of the family of real frogs. The lake frog is the largest species of amphibian fauna of Russia: its body length can reach up to 150 mm.

Tailless - the largest order of amphibians, numbering about 6000 modern and 84 fossil species. Often, representatives of the order are called frogs, but the use of this term is complicated by the fact that only representatives of the family of real frogs are called frogs in the narrow sense. Tailless amphibian larvae are tadpoles.

Class - Amphibians, detachment - Tailless, family - Frogs, Genus - Frogs.

Size 6-10 cm. Average weight 22.7 gr. The muzzle is blunt, the body is squat. The eyes are brown with black horizontal pupils. The inner eyelid is transparent, protecting the eyes in water. A dark brown triangle is clearly visible near the tympanic membrane. The skin of the frog is slimy and smooth to the touch, its epidermis does not keratinize. There is a marble-like pattern on the dark belly. Calcaneal inner tubercle is low.

In males, external resonators of a dark gray color are located in the corners of the mouth. On the first (inner) finger of the forelimbs, males have a skin thickening - a callus, which grows during mating.

Amphibians require oxygen to live. The frog can get it on land and partially under water through the skin. The respiratory organs of amphibians, which include frogs, are lungs, skin and gills. Unlike tadpoles, which are aquatic, adult frogs do not have gills. Oxygen dissolved in water enters the blood of these creatures through the skin. This way of breathing can provide the body with the necessary gas only if the frog is in a state of hibernation.

frog can long time be under water, because she has very large lungs. Before diving, the animal gains full lungs of air. Under water, oxygen is absorbed very slowly through the blood arteries, and this helps the frog to stay under water for a long time. As soon as the air supply runs out, the animal quickly emerges and keeps its head above the surface of the water for some time in order to regain full lungs of air.

Frogs never drink. Fluid enters their body through the skin.

An adult breeds in water, but prefers to spend most of its life on land, choosing very damp and shaded places to live.

On land, frogs hunt by catching insects, which are the main diet. In gardens located in the lowlands near water bodies, fruit trees, shrubs and vegetable crops are almost never affected by pests, since frogs are cleaning animals. Only a few frogs are capable of destroying hordes of insect pests.

The breeding season is April - early May. Reproduction occurs in puddles, reservoirs, lakes, canals, in any shallow reservoir. Spawning begins 3-5 days after awakening. Males appear on the reservoirs earlier, they sing mating songs, inviting females. Having spawned, the common frog does not linger in the reservoir and disperses to summer habitats. The eggs are light yellow in color, surrounded by a thick layer of gelatinous substance. This shell has great importance for the embryo, since in this way the egg is protected from drying out, from mechanical damage, and most importantly, it protects them from being eaten by other animals. They are connected in clusters of a rather significant size, and sometimes in cords; a lot of them are put off. One female lays 670-1400 small eggs.

Use in science

“And how many frogs are countless,
They can be counted and counted endlessly, -
They gave frog legs to science,
Hearts were given to science.”
L. Gainulina

Lake frogs are often caught as laboratory animals for scientific, medical and educational institutions.
For example, students of the Orenburg State Pedagogical University use up to 3,000 lake frogs to conduct workshops in physiology and zoology in one year of study.

Frogs have been found to have a lot of biologically active substances, but they are much less studied than toads.

It has long been known that if you put a frog in milk, then it will not turn sour for a very long time. Modern research the antimicrobial properties of the mucus covering the skin of the frog have been confirmed. This prevents the reproduction of sour milk bacillus.

Leather different types frogs managed to extract a number of substances with biological activity.

Some of these substances are effective in killing bacteria, while others have vasodilating properties. From the skin of the white Australian tree frog, a substance was isolated that has a choleretic effect, as well as stimulating the secretion of gastric juice. From this substance it is possible to make a drug for the treatment of certain mental illnesses.

In the skin of one of the species of frogs, dermorphins were found, which are 11 times more analgesic than morphine.

Frog neurotoxins are among the most powerful. Batrachotoxin, isolated from the Colombian frog, locally called "cocoi", is the most potent of the non-protein poisons, stronger than potassium cyanide. Its action is similar to that of curare.

Substances isolated from some South American tree frogs act on the transmission of nerve impulses in skeletal muscles. Some block smooth muscle receptors, while others cause skeletal and respiratory muscle spasms.

Currently, these substances are not used in medicine, the possibility of including them in clinical practice is being investigated.

The antimicrobial and wound-healing properties of frog caviar have received scientific confirmation - the substance ranidon, which has a high bactericidal activity, has been isolated from the shell of the caviar.

No matter how we feel about frogs, this is one of the most common, frequently used laboratory animals, along with rats and mice. For example, the clawed frog was the first cloned animal, and not Dolly the sheep, as we used to think. In the 1960s, the English embryologist Gurdon cloned tadpoles and adult frogs.

For merits in the field of medicine, monuments were erected to the frog in Paris, Tokyo and Boston, as a tribute to and recognition of the truly invaluable merits of these animals in the development of science. So scientists thanked their unwitting helpers in many important scientific research and discoveries. The experiments of the Italian physicists of the XVIII century Luigi Galvani and Alessandro Volta, carried out on frogs, led to the discovery of galvanic current. A huge number of experiments on frogs were carried out by the physiologist Ivan Sechenov. In particular, he used them in the study of the nervous activity of animals. And the frog's heart turned out to be an interesting object for the study of cardiac activity. The French physiologist Claude Bernard, who was also helped to make a number of discoveries by frogs, expressed the idea of ​​erecting a monument to him. And at the end of the 19th century, the first monument to frogs was opened at the Sorbonne (Paris University). And the second was erected by medical students in Tokyo in the 60s of the XX century, when the number of frogs they used for science reached 100 thousand.

In addition to scientific value, these amphibians have practical value. So in many countries meat certain types frogs are considered a delicacy. There are even special farms where frogs are bred for meat.

Practical work

So, getting started:

07.05.15 caviar was taken in a pond, surrounded by shrubs and aquatic plants.

The shell of each egg is swollen, similar to a gelatinous transparent layer, inside which an egg is visible. The upper half is dark and the lower half is light.

In nature, the rate of development of eggs depends on the temperature of the water. The higher the temperature, the faster the development. In deep, shaded reservoirs, eggs develop approximately four times slower than in well-warmed reservoirs. Caviar easily withstands low temperatures.

We create optimal conditions for the development of caviar: the water temperature is room temperature, warm.

After 8-10 days, tadpoles hatch from the eggs, more like fish fry. Passive, do not feed. Apparently there is enough nutritional reserve of eggs. There are gill openings and gills.

05/23/15 Noticeable metamorphosis. The tadpoles began to feed on their own, move actively, and keep close to each other. They scurry in different directions, but do not swim far, and the whole flock moves almost simultaneously. The average size tadpoles are about 7-8 mm.

By this time, the head, torso, and tail are already visible. The head is large, there are no limbs, the tail section of the body is a fin, there is also a lateral line, and oral cavity looks like a sucker. The gills are initially external, attach to the gill arches located in the pharynx, and already function as true internal gills.

The suction cup is located below the mouth (it can be used to determine the type of tadpole), after a few days the gap of the mouth along the edges is overgrown with some kind of beak, which works like wire cutters when the tadpole feeds. The tadpole has one circulation and a two-chambered heart.

In terms of body structure, amphibian larvae are close to fish, and adults resemble reptiles.

In nature, sometimes tadpoles form huge clusters - up to 10,000 in one cubic meter of water. Not without reason, among the ancient Egyptians, the image of a tadpole meant the number 100,000, that is, “a lot”. But not all of them survive. The frog larva serves as food for fish, birds, swimming beetles and other inhabitants of the reservoir.

We place tadpoles in different containers:

We place an absolutely transparent plastic container (10 l) in a well-lit area, in a warm place Not in the area of ​​direct sunlight (balcony) - 25 pcs.

We place an absolutely transparent glass container (3 l) in a well-lit area, in a warm place in the area of ​​direct sunlight (balcony) - 10 pcs.

We place a dark, opaque container (5 l) in a warm place, slightly shaded, but with enough light. No direct sunlight (room) - 30 pcs

We place an opaque container (2 l) in a poorly lit, cool place (garage) - 10 pcs.

All containers are filled with water taken from the caviar collection site, i.e. closest to the breeding conditions, as well as algae and grass. Microorganisms are observed in the water.

Within two days, no differences in behavior are observed. All tadpoles are mobile, hiding in mud and grass, actively reacting to sound and movement. They feed on plant foods during the day, as if biting off, and also scrape off plaque from the surfaces. Periodically rise to the surface of the water and swallow air. Growth rates are not striking, as you know, they average 0.6 mm per day.

05/25/15 In the glass container, located in the zone of direct sunlight, by the evening all the tadpoles died. At the same time, without preserving the contours of the body, almost completely decomposed and disappeared. Outwardly, the surface of the water in the container looked like it had bubbled up, as if sour.

Conclusion: tadpoles, despite the assertion that complete metamorphosis occurs faster with more high temperatures(21-26 C), and on average it lasts 50-90 days, do not tolerate direct sunlight.

We cover a completely transparent plastic container with paper, protecting it from the sun.

05/28/15 IN plastic container, even despite the fact that it is not under direct sunlight, tadpoles are passive, they are practically without movement. The water is very hot. Several pieces died. Move to a more shady spot.

In other containers, tadpoles are still active. Located almost in in constant motion and the process of nutrition.

The growth of tadpoles is already more noticeable. The average is about 10 mm.

We add fresh water and algae from the reservoir, but not from the place of masonry, to all containers with tadpoles.

06/01/15 In a transparent, well-transmitting daylight container, placed in the shade, the tadpoles increased in growth. There was a sharp difference between larger and smaller tadpoles. Large ones are approximately 13-15 mm. They eat all the time, stick to the walls, grab air. The eyes are clearly visible, the marble pattern of the body.

In an opaque container that practically does not let in daylight, but located in a warm place, the growth of tadpoles is practically not noticeable, as well as in a container located in a cool, dark place. Several died, despite the presence of food and the absence of direct sunlight.

Conclusion: there is a high mortality during the developmental period, even in the absence of external predators that feed on tadpoles.

Within 3 weeks with constant feeding and changing the water in containers, because. products of food processing by tadpoles accumulated at the bottom, the death of some specimens and the growth of stronger ones were observed. The average size is already about 20-25 mm.

The highest mortality was in a transparent container located in a warm place. Perhaps from a constant drop in water temperature: from very warm, heated by the sun during the day, to very cold at night.

06/27/15 The tadpole in the garage underwent visible metamorphoses: hind legs appeared.

07/03/15 Within a short period of time, the tadpole takes the form of a small frog. The front legs have grown, the tail has shortened. At the same time, the young frog outwardly turns out to be smaller in size than the tadpole from which it had just formed.

Thus, as in nature, about 2-3 months pass from the moment of laying eggs to the end of the transformation of a tadpole into a frog.

Frog metamorphosis: 1 - eggs (caviar), 2 - tadpole with external gills, 3 - without gills, 4 - with hind legs, 5 - with all legs and tail, 6 - frog.

The most successful of the tadpoles survive to the stage of metamorphosis and turn into a yearling frog. Underyearlings are very voracious. The volume of their stomach in a full state exceeds one fifth of the total weight. There is one interesting detail: if there is not enough animal food in the reservoir, the herbivorous tadpole winters in the larval stage, postponing the transformation from a vegetarian into a predator until spring. They become fully carnivorous once their hind legs develop, feeding on small aquatic animals or even other tadpoles when food is scarce.

07/05/15 As you know, in nature, tadpoles feed on algae, plant matter, and larvae of small microorganisms. In captivity, perhaps due to the lack of plant food (despite its presence in the container), the tadpoles ate the newly formed frog, and not vice versa.

Conclusion

Thus, we conclude that tadpoles are very fragile organisms. Our hypothesis was confirmed.

1. Mortality of eggs and tadpoles reaches 80.4 - 96.8%.

Of enough a large number hatched tadpoles, 11 survived. At the same time, 5 out of 30 - in a dark, opaque container (5 l), located in a room slightly shaded, without direct sunlight.

3 out of 10 - in a light, opaque container (2 liters), located in a poorly lit, cool place in the garage. At the same time, a frog was formed ahead of all.

• HAPPY BIRTHDAY, FROG!
• The birth of a frog most often occurs in ponds, lakes and other stagnant water bodies, because. This is where adult animals lay their eggs.

• Happy birthday, frog!

  Happy birthday, frog!
• Soon, tadpoles emerge from the eggs, which after a while will turn into frogs.
• You can read more about this.
• But this is only true for our common species, but in tropical rainforests, where the number of species even in a small area is in the tens, everything is completely different.
• Where frogs are visible or invisible, hunters for themselves, eggs and tadpoles will definitely appear. What to do? How to protect your offspring? To protect their eggs from voracious predators, some frogs have adapted to lay their eggs on land.
• THE BEST INVENTIONS OF NATURE.
• The female "glass" frog places eggs in the form of a gelatinous mass on the lower surface of a leaf hanging over a pond.
• The male guards the clutch until tadpoles appear. Coming out of the eggs, they slide off the leaf and fall into the water, where the transformation soon takes place - the birth of a frog.

• Glass frog caviar

  
  Glass frog caviar
• Mother nature is arranged in such a way that no living creature can find an absolutely reliable way to protect itself from predators.
• And yet, caviar laid on leaves or the ground is less dangerous than placed in water.
• To confuse predators, many species of tropical frogs spawn in the most unexpected places.
• FOAM HOUSE.
• South African frogs make a foam house for their offspring. When it comes time to spawn, they gather on the branches of trees overhanging any body of water.
• Females secrete a special viscous liquid onto a branch, and males beat it into foam, working with their hind legs. In such a foamy nest, the females lay their eggs to continue their kind and give birth to babies. The outer layers of the foam dry up, and the laid caviar is protected from all sorts of troubles.

• foam house

  
  foam house
• Despite the seeming unreliability, the foam house is one of the best inventions in the animal world. Firstly, the foam smooths out changes in temperature and humidity, and secondly, it does not arouse suspicion among predators: there is hardly anything edible hiding inside.
• After a few days, tadpoles hatch from the laid eggs, the nest begins to disintegrate, they go outside and fall into the water, where the frog is then born.
• This method of survival is used not only by frogs, but also by many insects - leafhoppers, grasshoppers and.
• YOUR POOL.
• And the South American poison dart frogs (familiar for their poisonousness) have adapted to carry the cubs on their backs. First, they lay their eggs on moist soil and jealously guard future offspring. Then, the hatched tadpoles sit on the back of the parent and the adult frog climbs the tree with its burden.

• Own pool

  
  Own pool
• But why? She is looking for bromeliad - a plant that attaches to a tree, where the leaves form a funnel at the base, where water collects during the rains, and a semblance of a small pond forms high in the branches. When the poison dart frog finds a suitable body of water, the tadpoles unhook and fall into the water.
• It is not easy for predators to get into such a shelter, and tadpoles can easily develop.
• LIKE A KANGAROO?
• The pygmy marsupial tree frog has a completely unusual way of giving birth to offspring. The laid eggs develop in a special skin pocket in the protrusions on the back of the female. Here, future babies are protected from enemies and from drying out.
• When the time comes for the birth of tadpoles, the female finds the same bromeliad and descends into the water. Water penetrating into the bag serves as a signal for tadpoles to go outside.

• marsupial tree frog

  
  marsupial tree frog
• One of the species of marsupial tree frogs also has a skin fold - like a kangaroo pouch - only located backwards. When laying eggs, the mother frog puts them in her pocket with her hind legs and the hatched tadpoles remain there.
• Only when they turn into frogs do they leave their safe haven.
• MIRACLE CAVIAR.
• The birth of a rain frog occurs in its own way: the female lays her eggs on the forest floor - in the moss, under rotten leaves, by the stream, where there is no danger of drying out.
• The eggs of this frog (compared to others) are of enormous size with a supply of nutrients.

• Miracle caviar

  Miracle caviar
• Therefore, the tadpole can stay in the egg longer than usual - after all, he does not have to take care of his food.
• Without leaving the egg, the tadpole turns into a small, fully formed frog, ready for adulthood.
• TAKEN AND SWALLOWED!
• But Darwin's tree frog literally swallows her offspring, but not in order to eat, but in order to protect future frogs.

• Darwin's tree frog with a newborn

  
  Darwin's tree frog with a newborn
• The female lays her eggs on the ground, and the male sits down to guard her, and as soon as the tadpoles are about to come out, he places the eggs in a special pocket in the throat.
• They stay there until they turn into little frogs, and then they get out and begin an independent life.
• So, in a completely different way, the birth of a frog occurs.

February 12, 2017

In this article, we will consider the stages of frog development. But first, let's talk a little about what these creatures are. The frog belongs to the class of amphibians, the order of anurans.

Many noticed that her neck was not expressed - it seemed to have grown together with the body. Most amphibians have a tail, which the frog does not have, which, by the way, is reflected in the name of the detachment.

The development of a frog takes place in several stages, we will return to them immediately after we analyze some of the features of these creatures.

What does a frog look like

For starters, the head. Everyone knows that the frog has rather large and expressive eyes located on both sides of its flat skull. Frogs also have eyelids; this feature is inherent in all terrestrial vertebrates. The mouth of this creature has small teeth, and a little above it are two nostrils with small valves.

The forelimbs of frogs are less developed than the hind limbs. The first have four fingers, the second - five. The space between the fingers is connected by a membrane, there are no claws.

The development of a frog takes place in several stages:

1. Caviar throwing.
2. Early stage tadpoles.
3. Late stage tadpoles.
4. Adult individuals.

Their fertilization is external - the males fertilize the eggs already laid by the female. By the way, there are species that lay more than 20 thousand eggs in one throw. If everything goes well, then ten days later tadpoles are born. And after another 4 months, full-fledged frogs are obtained from them. Three years later, a mature individual grows up, which is completely ready for reproduction.

Now a little more about each stage.

Caviar

Now we will analyze all the stages of frog development separately. Let's start with the very first - eggs. Although these creatures live on land, during spawning, they go into the water. This usually happens in spring period. Masonry takes place in quiet places, at a shallow depth, so that the sun can warm it up. All eggs are interconnected, and this mass resembles jelly. One teaspoon is barely enough from one individual. All this jelly mass is necessarily attached to the algae in the pond. Small species lay about 2-3 thousand eggs, large individuals - 6-8 thousand.

The egg looks like a small ball, about 1.5 millimeters in diameter. It is very light, has a black shell and increases in size over time. Gradually, the eggs move on to the next stage of frog development - the appearance of tadpoles.

tadpoles

After birth, tadpoles begin to feed on the yolk, which still remains in small quantities in their intestines. This is a very fragile and helpless creature. This individual has:

• poorly developed gills;
• tail.

Tadpoles, in addition, are equipped with small Velcro, with which they are attached to various water objects. These Velcro are located between the mouth and abdomen. In the attached state, the babies are about 10 days old, after which they begin to swim and eat algae. Their gills gradually overgrow after 30 days of life and, as a result, are completely covered with skin and disappear.

It is also important to know that even tadpoles already have the small teeth needed to eat algae, and their intestines, arranged in the form of a spiral, allow them to extract as much as possible nutrients from eaten. In addition, they have a chord, a two-chambered heart and blood circulation in the form of a single circle.

Even at this stage of frog development, tadpoles can be considered quite social creatures. Many of them interact with each other like fish.

The appearance of the legs

Since we are considering the development of a frog in stages, the next step is to single out tadpoles with legs. Their hind limbs appear much earlier than the front ones, after about 8 weeks of development - they are still very tiny. In the same period, you can notice that the head of the kids becomes more distinct. Now they can eat larger prey, such as dead insects.

The forelimbs are just beginning to form, and here one can single out such a feature - the elbow appears first. Only after 9-10 weeks will a full-fledged frog form, however, much smaller than its mature relatives, and even having long tail. After 12 weeks, it completely disappears. Now the little frogs can go on land. And after 3 years, a mature individual will form and will be able to continue its genus. We'll talk about this in the next section.

adult

After three long years have passed, the frog can reproduce into the world. This cycle in nature is endless.

To consolidate, we once again list the stages of development of the frog, the scheme will be our assistant in this:

a fertilized ovum represented by an egg - a tadpole with external gills - a tadpole with internal gills and skin respiration - a formed tadpole with lungs, limbs and a gradually disappearing tail - a frog - an adult.

Among many animals, only the so-called invertebrates reproduce asexually. Vertebrate animals - such as mammals, fish, reptiles, birds and amphibians - reproduce sexually: spermatozoa and eggs, which carry hereditary material typical for this species, are combined during fertilization. A fertilized egg is called an embryo.

Depending on the type of animal, the embryo can develop both in the mother's body and outside it. Gradually, little cubs develop from fertilized eggs in accordance with the genetic guidelines laid down in it. Many, like frogs, go through another developmental stage before becoming fully grown.

From egg through larva to adult

Snails live on land, in running water and in the seas. Sea slugs lay their eggs in sea ​​water, which, after high tide, get stuck between the rocks. The fertilized eggs hatch into larvae (veligers) that can swim. They swim with the current and finally sink to the rocky bottom, where they turn into adult crawling clams.

fertilized egg

The red spot in the middle of the egg yolk is a three-day-old chicken embryo. A week later, the embryo already takes the form of a chicken. A month later, the chick is already fully developed and covered with soft fluff. With an egg tooth on his beak, he breaks the egg shell and comes out into the light. The chick is hatched and becomes an adult without any additional developmental stage.

From egg to tadpole

During the mating season, many frogs gather in large noisy groups. Females respond to loud calls from males. Only a few species of frogs give birth to live young; most species lay their eggs (spawn) in or near water. The number of eggs depends on the type of frog and ranges from one to twenty-five thousand. As a rule, the eggs are fertilized outside the body of the frog and left to their own devices. When the egg matures, a small tadpole hatches from it. Tadpoles live in water and breathe through gills like fish. Only in a few species of frogs do females take care of their offspring.

Frogs and toads

Unlike adult frogs, tadpoles are herbivorous and feed on aquatic plants and algae. After a certain time, an amazing transformation (metamorphosis) occurs in the development of the tadpole: the fore and hind limbs appear, the tail disappears, the lungs and eye eyelids develop, as well as new system digestion, designed to digest animal food.

The rate of transformation is different in different species, the main factor here is the temperature of the water. In some toads and frogs, metamorphosis occurs in a few days or weeks, while in others it takes several months. The tadpole of the North American bullfrog does not fully develop until after a year or more.

Frogs and toads belong to the class of amphibians and to the same group of anurans, but they differ appearance and way of life. Frogs have soft skin and are good jumpers, while toads are covered in warts and tend to crawl. There are over 3,500 species of frogs and toads on earth. With the exception of Antarctica, they can be found on every continent. They prefer to live in tropical and subtropical zones where more than 80% of all species live. But wherever they live, in deserts or mountains, savannahs or tropical rainforests, they must return to the water in order to procreate.

What is metamorphosis

In their development, frogs go through three stages: from an egg to a tadpole, and then to an adult frog. This process of development is called metamorphosis. Many invertebrates also pass through the stage of larvae in their development. However, the most amazing changes occur in the life of insects: butterflies and beetles, flies and wasps. Their life is divided into four stages, very different from each other in terms of nutrition and habitat: egg, larva, pupa, adult insect. The larva looks completely different from the adult insect and has no wings. Her life is completely focused on growth and development, and not on procreation. Only after the larva pupates does it become an adult insect.

The frog turns into a prince only in a fairy tale. But don't the transformations that a frog undergoes during its life cycle demonstrate evolution? From a fish-like tadpole (which even has gills), the “baby frog” quickly “transforms” into a completely new form to start leading a radically new lifestyle! The mouth becomes wider, the tail dissolves, but an "elastic" tongue is formed for catching flies, and nostrils appear, and bulging eyes move to another place on the head. Finally, when the lungs finally mature and four legs grow, this matured tadpole celebrates its “coming of age” by jumping out of the water to now live on land.

This amazing transformation (metamorphosis) is far from being just external. Almost all organs and systems of the body undergo a radical restructuring. For example, a complete reconfiguration of the nervous system is needed to control new or reprogrammed organs - eyes, ears, paws, tongue, etc. A similar reorganization must also take place at the biochemical level. Changes in hemoglobin in the blood, light-sensitive pigment in the eyes, among many other changes. Even the excretory (excretory) system of the frog is changing in order to fit the new way of life.

Biologists are puzzling over the mega-complexity of this "rebirth" that occurs in ordinary ponds. A frog basking on a water lily leaf is an amazing result of many changes occurring sequentially with amazing accuracy in the right order. It would not be an exaggeration to say that the opening ceremony Olympic Games simply pales in comparison with the "choreography" of the process of metamorphosis of the frog. The life of a tadpole would certainly become more difficult if, for example, its tail disappeared before the legs grew. The same applies to his internal organs, bones, nervous system, biochemical processes, etc. Any failure can stall the entire process of reorganization of the organism ... and lead to rather unfortunate results (for a tadpole)!

photolibrary.com

Very difficult program

The fantastically complex information encoded in the DNA that allows a tadpole to turn into a frog clearly points to the Higher Intelligence that created it. Such a program cannot be formed naturally- it demonstrates the originally intended end result.

All steps are interconnected

Years of research have uncovered several levels of processes required to effect this "transformation of life." For example, the disappearance of the tail requires a precisely programmed execution of micrologistics operations. First, the tadpole stops the formation of tail muscle cells. It then produces a series of highly specific enzymes that dissolve tail cells.

Then, at the right moment, these "little killers" are combined and injected into tail cells of all types. Finally, roaming macrophages engulf these dead cells so that they can then reuse their components and nutrients in other parts of the body (i.e., the tail is not shed, but reabsorbed by the body).

"Change" does not mean "evolve"

So how justified is the assertion that this is an example of " evolution in action"? Is the transformation of a tadpole into a frog good example evolution?

Quite the opposite! Although the tadpole may look like a real "fish" in appearance, it is a frog from its very birth. Everything that he needs for rebirth (that is, all genetic information, schemes and programs) is already embedded in the DNA code stored in the nuclei of the tadpole's cells. At this micro level, we find not only a complete plan for the development of a frog, but also a fully functional factory with all the necessary mechanisms and equipment to bring this plan to life.

The genome of a fish does not contain the information needed to become an amphibian, and there is nowhere for it to get such information from.

This embedded information is the key difference between the evolutionary tale (as if a fish evolved into an amphibian) and the real world (in which a tadpole turns into a frog). From the very moment of its birth from an egg, the tadpole is already equipped with a complete set of instructions "how to turn into a frog on your own." In contrast, fish only contain the genetic instructions for "building"... fish! The genome of a fish does not contain the information needed to become an amphibian, and there is nowhere for it to get such information from. In fact, it is doubtful that there is even one undisputed example of how evolutionary mechanisms introduced new information into the genetic blueprint of any creature.