What does a frog use to move? About the movement of amphibians. Drawing a Frog with Rapidographs on Gray Paper

Frogs and their close relatives, toads, are amphibians, that is, vertebrates that spend part of their lives on land and part in water. Most of the 3.5 thousand amphibians are frogs. From a biological point of view, there is almost no difference between frogs and toads. Frogs have smoother skin, longer hind legs and well-developed membranes between the toes. Toads have a more rounded body, dry, often warty skin and short hind legs, suitable for crawling and short jumps. The membranes on their hind legs are underdeveloped, since water is not their element. Frogs and toads belong to the order of tailless amphibians that appeared on the planet about 150 million years ago.

Appearance

The body temperature of cold-blooded frogs is always equal to environment, so they are cold and slippery to the touch. The frog's head is wide and flat, with a very wide mouth. She has 4 toes on her front paws, and 5 on her hind paws. The toes are connected by a thin leathery membrane. In some aquatic species, the big toes of the hind feet are armed with sharp claws for tearing prey. Most frogs lead night look life.

Methods of transportation

Thanks to the long and strong legs The frog is an excellent jumper. To do this, she first rises on her front legs, and then, pushing off powerfully with her hind legs, flies into the air. Hymenoptera frogs spend almost their entire lives in water. Some tree-dwelling frogs do not have membranes, but they have a round suction cup on the tip of each finger. Its surface covered with rough skin allows the frog to easily climb tree bark.

Reproduction

Almost all frogs lay their eggs in water. In one lump of caviar there are several thousand small eggs, several millimeters in diameter, each of which is enclosed in a foamy protective shell. The shell protects the eggs from predators, but some frogs have developed their own methods of caring for their offspring. They lay much fewer eggs, but they take care of them sparing no effort. Thus, before the start of the rainy season, the blacksmith tree frog fences off a small pond near the shore of a reservoir, where it lays its eggs. Tadpoles appear there in complete safety, and with a flash flood they swim away into a river or lake.

Development of tadpoles

The tadpole's hind legs form at the base of the tail. The forelimbs are still hidden under gill covers and break out later, and not always at the same time, so you often see three-legged tadpoles. Having acquired all its limbs, the tadpole becomes more and more like a frog. The shape of the mouth changes, the eyes protrude, the tail turns into a short appendage. At this stage of development, the frog decides to leave the water for the first time. Some frogs lay their eggs on land - under leaves or stones. After a few weeks, bypassing the tadpole stage, they hatch into fully formed frogs. Selected species frogs show real miracles of parental care. For example, the land-dwelling helmeted frog, as well as the males of some South American poison dart frogs, carry eggs on their backs, where they hatch.

Kids in a backpack

Some tree frogs, including the marsupial tree frog, have gone even further in this important matter. The female has a spacious pouch on her back, where her caring father helps place the eggs. The tadpoles develop right in the bag, living off the yolk reserves in the stomach, and after a few weeks, tiny copies of the happy parents emerge from the bag.

Nutrition

The basis of the frog's diet is live, mobile prey, primarily insects, the size of which depends on the width of the mouth and the dimensions of the hunter himself. Thus, the American bullfrog eats everything it can swallow, including poisonous snakes, giant centipedes, scorpions and even their relatives. Seeing the prey, the frog overtakes it with a lightning-fast throw. The prey stuck to the sticky tongue is swallowed whole, while the frog blinks frequently and the eyeballs drop into the oral cavity, helping to push the food into the pharynx.

Self-defense

Frogs are a tasty treat for many animals, and in order to protect themselves from predators, they have to resort to all sorts of tricks. Some boldly rush at the enemy with their toothless mouth wide open. This technique is especially effective when performed by a bullfrog, whose mouth can easily fit a human fist. Not every predator can resist such psychic attack. Other species rely on camouflage or, conversely, flashy colors. Thus, many tree frogs cannot be distinguished from a leaf or piece of bark when they are motionless, but during a jump, a bright spot on the abdomen or hind legs suddenly flashes before the eyes of the predator, and the tree frog only needs a moment of confusion to hide.

Popular delicacy

Culinary experts in many countries around the world consider frogs an exquisite delicacy. For example, in French restaurants, frog legs are served as a signature dish. However, the edible frog has become such a rarity these days that huge quantities of frogs are imported from Asia to meet the growing demand. IN North America The bullfrog with its fleshy hind legs is highly valued. They usually go out to collect frogs at night, blinding them with the beam of a flashlight.

Frogs and their close relatives, toads, are amphibians, that is, vertebrates that spend part of their lives on land and part in water. Most of the 3.5 thousand amphibians are frogs. From a biological point of view, there is almost no difference between frogs and toads. Frogs have more smooth skin, the hind legs are longer and the membranes between the toes are well developed. Toads have a more rounded body, dry, often warty skin and short hind legs, suitable for crawling and short jumps. The membranes on their hind legs are underdeveloped, since water is not their element. Frogs and toads belong to the order of tailless amphibians that appeared on the planet about 150 million years ago.

Appearance

The body temperature of cold-blooded frogs is always equal to the ambient temperature, so they are cold and slippery to the touch. The frog's head is wide and flat, with a very wide mouth. She has 4 toes on her front paws, and 5 on her hind paws. The toes are connected by a thin leathery membrane. In some aquatic species, the big toes of the hind feet are armed with sharp claws for tearing prey. Most frogs are nocturnal.

Methods of transportation

Thanks to its long and strong legs, the frog is an excellent jumper. To do this, she first rises on her front legs, and then, pushing off powerfully with her hind legs, flies into the air. Hymenoptera frogs spend almost their entire lives in water. Some tree-dwelling frogs do not have membranes, but they have a round suction cup on the tip of each finger. Its surface covered with rough skin allows the frog to easily climb tree bark.

Reproduction

Almost all frogs lay their eggs in water. In one lump of caviar there are several thousand small eggs, several millimeters in diameter, each of which is enclosed in a foamy protective shell. The shell protects the eggs from predators, but some frogs have developed their own methods of caring for their offspring. They lay much fewer eggs, but they take care of them sparing no effort. Thus, before the start of the rainy season, the blacksmith tree frog fences off a small pond near the shore of a reservoir, where it lays its eggs. Tadpoles appear there in complete safety, and with a flash flood they swim away into a river or lake.

Development of tadpoles

The tadpole's hind legs form at the base of the tail. The forelimbs are still hidden under the gill covers for some time and break out later, and not always at the same time, so you often see three-legged tadpoles. Having acquired all its limbs, the tadpole becomes more and more like a frog. The shape of the mouth changes, the eyes protrude, the tail turns into a short appendage. At this stage of development, the frog decides to leave the water for the first time. Some frogs lay their eggs on land - under leaves or stones. After a few weeks, bypassing the tadpole stage, they hatch into fully formed frogs. Certain species of frogs show real miracles of parental care. For example, the land-dwelling helmeted frog, as well as the males of some South American poison dart frogs, carry eggs on their backs, where they hatch.

Kids in a backpack

Some tree frogs, including the marsupial tree frog, have gone even further in this important matter. The female has a spacious pouch on her back, where her caring father helps place the eggs. The tadpoles develop right in the bag, living off the yolk reserves in the stomach, and after a few weeks, tiny copies of the happy parents emerge from the bag.

Nutrition

The basis of the frog's diet is live, mobile prey, primarily insects, the size of which depends on the width of the mouth and the dimensions of the hunter himself. Thus, the American bullfrog eats everything it can swallow, including poisonous snakes, giant centipedes, scorpions and even its relatives. Seeing the prey, the frog overtakes it with a lightning-fast throw. The prey stuck to the sticky tongue is swallowed whole, while the frog blinks rapidly and the eyeballs drop into the oral cavity, helping to push the food into the pharynx.

Self-defense

Frogs are a tasty treat for many animals, and in order to protect themselves from predators, they have to resort to all sorts of tricks. Some boldly rush at the enemy with their toothless mouth wide open. This technique is especially effective when performed by a bullfrog, whose mouth can easily fit a human fist. Not every predator can resist such a psychic attack. Other species rely on camouflage or, conversely, flashy colors. Thus, many tree frogs cannot be distinguished from a leaf or piece of bark when they are motionless, but during a jump, a bright spot on the abdomen or hind legs suddenly flashes before the eyes of the predator, and the tree frog only needs a moment of confusion to hide.

Popular delicacy

Culinary experts in many countries around the world consider frogs an exquisite delicacy. For example, in French restaurants, frog legs are served as a signature dish. However, the edible frog has become such a rarity these days that huge quantities of frogs are imported from Asia to meet the growing demand. In North America, the bullfrog with its fleshy hind legs is highly prized. They usually go out to collect frogs at night, blinding them with the beam of a flashlight. http://bufodo.apus.ru

Good morning!

In the final part of the trilogy on smooth reinforcement, I want to talk about steel reinforcement fasteners - bent or welded elements that ensure the design position of the reinforcement.

The designer can beautifully draw the upper and lower reinforcement in the slab, but it will not hang in the air - you need to order supporting elements in the project - bent “frogs” or welded frames. Why should a designer do this? Firstly, there is a clear indication in SNiP “Concrete and reinforced concrete structures”, clause 5.49: “Compliance of the location of the reinforcement with its design position must be ensured by special measures (installation of plastic clamps, washers made of fine-grained concrete, etc.)”, and since it is written in SNiP, then the designer must take care of this in the project. Secondly, who, if not the designer, knows what supporting elements will reliably secure the frame in the design position? If we leave the choice to the will of the builders, then they will support the upper reinforcement in an 800 mm thick slab with bent “frogs” from six or even tied vertical rods (I give examples from life). And no one can predict where this reinforcement will move during concreting.

So, let's talk about steel fasteners in reinforced concrete slabs.

If the thickness of the slab is 200 mm or less, the upper knitted mesh in it will be perfectly supported by clamps, which builders lovingly nicknamed “frogs”, “toads”, etc.

These elements are made from smooth eights or tens and are installed in 600 mm increments in a checkerboard pattern - this is enough to prevent the upper mesh from bending even from the smallest diameter reinforcement. The dimensions of such a “frog” are usually as follows:

The length of the lower bends is equal to 1.5 steps of the lower reinforcement plus 15-20 mm - then the “frog” can be clearly fixed by bending it under the rod of the working reinforcement, as shown in the figure above. It should be noted that builders often do not place the ends of the “frogs” under the mesh rods, but simply lay it on top of the mesh and secure it with binding wire. With this scheme, the difference in the length of the vertical part of the frog will be noticeable - this can be seen from the figure below.

And since the “frog” from the dozen is a very rigid element, you cannot bend it manually, the dimensions and sketch of the “frog” must be clearly specified in the project. Let's say the figure shows a slab 180 mm thick, reinforced with twelve. At the same time, the difference in the vertical part of the frog was 10 mm (the blue one is 10 mm shorter than the pink one). Let’s say you took into account the “pink” option in the project, and the builders chose the “blue” one, in which case the upper mesh will be 10 mm higher than the design position, and the protective layer will clearly not be enough for it.

I give these examples so that you can weigh for yourself and choose how clearly and in detail to draw the fasteners in the project, so that in the end the builders don’t get carried away and come asking, what to do about it now? Only if the project provides comprehensive information, the builder will not shift the blame from himself to the designer.

The length of the vertical part of the frog must be clearly calculated depending on the position of the reinforcement bars in order to provide a protective layer for the upper reinforcement. Even the direction of the reinforcement bars significantly affects the height of the “frog” - see figure:

The width of the top shelf of the “frog” is usually taken to be 200 mm: if it is less, it is more difficult to bend; if it’s more, there’s no point.

As a result, reinforcement workers can calmly walk along the mesh, supported by properly made clamps, without fear of breaking their legs (and this is very important), and the concrete will not disturb its position.

If the slab thickness is from 200 to 500 mm, welded support frames should be used in the form of two ladders, which are placed on top of each other and form a stable support structure (see Fig. 44 of the design manual).

These ladders are made of smooth tens and are installed at an angle to the vertical axis of 30 degrees. In this case, welding may not be contact welding, but manual arc welding, because This fitting works one-time - during the installation period, and is not a working fitting. The pitch of the transverse rods in the frame is usually 300mm. The length of ladders is usually taken from 1 to 2 m - the main factor here is convenience for the builder.

When developing a frame, it is important to correctly calculate its height and at what distance from the edge the longitudinal rods are welded - it is on them that the reinforcement will rest. The frame is placed directly on the formwork, tilted, and another frame rests on it - the result is a stable triangle (this can be seen from the figure):

The second option for frames in thick slabs is the same ladders, only bent in plan into a triangle. They are stable, and with them it is much easier to clearly lay the top mesh at the required height - as specified in the project. Please note that the figure above shows a section of the slab, and below is a plan; for some reason, for many this figure in the manual turns out to be a rebus.

It is very convenient to place such frames in a tape (as in the figure) and in a slab. The main thing is to decide on their step. In general, the pitch of any supporting frames is calculated from the condition that the reinforcement of the upper mesh does not sag under the weight of a person and under the weight of pouring concrete. Therefore, the pitch directly depends on the diameter of the upper mesh rods. You can select it according to Figure 122 of the manual.

This is how these frames can be positioned in plan: on the left - in the slab, on the right - in the tape.

That's all about supporting reinforcement for today.

Happy designing!

Sincerely, Irina.

But first, let's talk a little about what these creatures are. The frog belongs to the class of amphibians, the order of tailless.

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

The development of a frog takes place in several stages; we will return to them immediately after we examine 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 common to all terrestrial vertebrate creatures. The mouth of this creature has small teeth, and slightly above it there are two nostrils with small valves.

The forelimbs of frogs are less developed compared to the hind limbs. The first have four fingers, the second have 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. Adults.

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

Now a little more about each stage.

Caviar

Now we will analyze all stages of frog development separately. Let's start with the very first thing - the egg. Although these creatures live on land, when they spawn, they go into the water. This usually happens in spring period. The masonry takes place in quiet places, at shallow depths, so that the sun can warm it up. All eggs are connected to each other, and this mass resembles jelly. From one individual there is barely one teaspoon of it. All this jelly mass is necessarily attached to the algae in the pond. Small species lay approximately 2-3 thousand eggs, large individuals - 6-8 thousand.

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

Tadpoles

After birth, the 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 the help of which they are attached to various aquatic objects. These Velcro are located between the mouth and abdomen. The babies remain attached for about 10 days, after which they begin to swim and eat algae. Their gills gradually become overgrown after 30 days of life and, eventually, are completely covered with skin and disappear.

It is also important to know that even tadpoles already have small teeth necessary to consume algae, and their intestines, arranged in the form of a spiral, allow maximum extraction nutrients from what was eaten. In addition, they have a notochord, a two-chambered heart and a single circle circulation.

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

Appearance of legs

Since we are considering the development of a frog in stages, the next step is to identify tadpoles with legs. Their hind limbs appear much earlier than their front ones, after about 8 weeks of development - they are still very tiny. During this same period, you may notice that babies’ heads become more distinct. Now they can eat more big catch eg dead insects.

The forelimbs are just beginning to form, and here we can highlight such a feature - the elbow appears first. Only after 9-10 weeks will a full-fledged frog be formed, although much smaller than its mature relatives, and even with a long tail. After 12 weeks it completely disappears. Now small frogs can go onto land. And after 3 years, a mature individual will form and will be able to continue its lineage. We'll talk about this in the next section.

Adult

After three many years, the frog can reproduce offspring into the world. This cycle in nature is endless.

To reinforce this, let us once again list the stages of frog development; the diagram will help us with this:

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

Pencil drawing tree frog in a few steps.
You will need: a soft pencil, drawing paper, an eraser and a flat surface for drawing.

The first step in drawing a frog is to draw a simple oval to represent its body. It's not a perfect oval, it's a little narrower at one end, almost like an egg. The narrow part will be the back of the frog, and the wide part will be the front.

Draw another small egg-shaped oval that overlaps the first one. Here the narrow end will be directed in the other direction. This oval will be the head of your frog.

On the smaller oval you just drew, draw two small circles. One is near the outer side of the oval (crossing the outline of the oval), the other is in the middle. These will be the frog's eyes. The circle in the middle of the oval should be slightly larger than on the outside, because this will be the eye facing the observer.

In the lower part of the frog's body you need to draw three ovals that form the front leg. You can see in the image how these ovals should be positioned. Oval #1 is the smallest and attached to the body, #2 is the largest, and #3 is almost a circle. These three ovals should be arranged in a "C" shape.

In order to depict the frog's hind legs, we will repeat the same process as in the previous step. The main difference is that the ovals that make up the frog's hind legs are about twice the size of the front ones.

Using the same principle, we draw the legs on the other side of the frog’s body. The frog's second front leg is partially hidden, with only part of the simple circle visible from behind the frog's neck area.

At the end of each of the frog's front legs you need to make three long fingers with circles at the ends. Repeat this process for the frog's back leg, only add four toes instead of three.
There is no need to draw toes on the back leg, which is facing away from the viewer. These fingers will be hidden from view.

Once you've erased all the intersecting lines inside the shapes, you'll be left with a nearly finished frog drawing.

Looking at the image, you can see that the smaller eye has been erased and connected to the rest of the head. This is because this eye faces away from the viewer.

On this moment Your frog is almost ready. All that's left to do is add a horizontal line to the frog's eye, nostril, mouth line and other small details. To separate the back from the stomach, draw a thin wavy line.