The energy obtained from the flapping of the wings of cyborg beetles. Lesson on the topic "The reason and meaning of warm-blooded birds" Lesson on the topic "The reason and meaning of warm-blooded birds"

Large birds that can glide well use wings to fly in warm weather only occasionally, using updrafts of heated air to maintain a stable soaring flight. These strokes, plus the bird's well-developed running legs, used for the takeoff run, allow it to gain the necessary speed for the wing lift to come into play. Small birds and insects work their wings almost all the time of flight, and at a relatively constant frequency of flapping. Their wings work like a propeller with an instantly reversible pitch at the extreme points of the strokes, when taking off along a special trajectory and at high angles of attack, rather back and forth than up and down, which is necessary to create forward and upward thrust, usually taking off against the wind . And they usually fly over short distances ...

In combination with the flexibility of the wings and a sufficient frequency of flapping during the operation of the flapping wings, a vortex, turbulent wave of a certain structure is created. Vortices for such a wave in the process of horizontal flapping flight are created by oscillating wings in opposite phases of flapping, and the resulting wave from these vortices contributes to their flight. In the process of constant oscillations, the wave of vortices created by the wings in its antiphase is caught by the wings, pushing them like air springs, and on the basis of this aerodynamic resonance, the further flight of these flying creatures occurs after takeoff.

At the resonance of such an aerodynamic oscillatory circuit, which consists of the energy of the muscles oscillating the wings (pump energy); from oscillating wings, which create a kind of springs in the form of vortex waves excited by the wings; from the vortices that fly off the wing and, in antiphase of the aerodynamic resonance, additionally push the wings and create a lifting force sufficient for the flight of an insect or bird, necessary for the flight. Without such an oscillatory circuit, tuned to aerodynamic resonance, economical flapping flight will be impossible!

It is this ADDITIONAL pushing of the oscillatory system formed by the wave of the excited environment, together with the aerodynamic shape of the oscillatory circuit itself, that is the essence of the economical operation of such an aerodynamic oscillatory system! It is only important to create such a wave and be able to tune the oscillatory circuit into resonance with the driving force and the excited wave of the medium with minimal energy consumption, avoiding the separation of the oscillatory system itself for its good and stable operation.

Evolving over hundreds of millions of years, insects have acquired a fairly perfect and at the same time relatively simple apparatus for flying in the air. By regulating the air flows created by the wings, the insect, like a helicopter, changes the direction of flight, creating the necessary thrust for horizontal flight, which already consumes somewhat less energy in accordance with the laws of classical aerodynamics, because due to its lightness and small size, it is used to some extent the lift of their well-blown hull.

Flying beetles also use elytra for horizontal flight, when they work like airplane wings, and the flapping insect wings themselves are like propellers, and by controlling the direction of all aerodynamic forces, the insect maneuvers in the air, and all the bristles and irregularities on the surface of the wings and elytra work to form the necessary turbulence for a continuous flow of air, providing a stable and economical flight. In some beetles, the elytra also wave a little, creating additional lift.

Many graduates in the field of flight did not know these subtleties for a long time and still do not fully understand them. But it took nature tens of millions of years to set up such an aerodynamic resonant oscillatory circuit, and today, in order to create a reliable aircraft with flapping wings for human flight, it is necessary to conduct many experiments, build tables of measurements and derive a certain scientific algorithm for applying scientific research in practice. Although even before the Second World War, German aircraft designers successfully launched small light ornithopters using a twisted rubber band to drive.

The famous aerodynamicist Alexander Lippisch was also fond of this, and in 1930 Eric von Holst managed to build an ornithopter, on which he installed an internal combustion engine and he flew on a long cord until the fuel ran out. On the lunge, the Kiselev flyweight built at the Moscow Aviation Institute also flew. But to create a reliable aircraft with flapping wings for human flight, so far no one has succeeded ...

People often imagine the flywheel as a machine capable of taking off almost vertically and even hovering in the air like a helicopter. It's a delusion. A flying machine is an aircraft capable of flying for a relatively long time without descending with the help of flapping wings. And how it takes off - with the help of a tugboat, from a wheel drive, using a jet engine, or simply from an elevation with the help of the pilot's legs, as Lilenthal did on his wings, then it does not matter. The important thing is that on such an apparatus you can fly like a bird!

It is clear that an eagle cannot fly into a calm without the help of its legs, and an albatross, if it is not on a hill, can run tens of meters in a calm before it rises to the wing! For this reason, swallows and swifts do not land on the ground at all, and they are good flyers!

Sometimes people ask how fast you need to flap your wings.

Speed ​​is the way to time. What speed are we talking about in the oscillatory process?

Although we can say that at the speed of planning.

The oscillation frequency depends on the frequency of natural oscillations of the entire wing-air system, and with the resonance of the mechanical oscillatory system as such, the stroke frequency can change very slightly. This will depend on the speed of the air flow around the wing, as well as on the elasticity and flexibility of the wing, and when other parameters of the entire oscillatory system change. That is why such a resonance is called parametric, that when some parameters change, other parameters of the entire oscillatory system change. You can also change the amplitude of wing oscillations to increase the speed of the wing in the oncoming air flow to increase its lift, as far as the mechanism itself, the material of the wing and the flight conditions allow.

And since any oscillatory system has its own quality factor for attenuation and works depending on the frequency and power of the driving force, on the elasticity and rigidity of the wing material, on the power of the driving force for the occurrence of resonant oscillations, the parameters of the entire oscillatory system can also change. By the way, all these parameters can also be changed, that is, if some parameters change in an oscillatory system, then the resonance of such an oscillatory system is called parametric.

Now about the necessary effort to flap for flapping flight. Sometimes it’s enough to look at what angles of attack a rooster takes off on a fence, so for a short time even roosters are able to take off from a place on a high fence, but I didn’t see them fly well, which means that it doesn’t have enough strength for horizontal flight, but it runs with the help of wings faster than without them. After all, he takes off on the fence and precisely thanks to the flapping of his wings! And when he runs, he helps himself with wings and run faster and maneuver better. But a black grouse or capercaillie can fly quite far after an almost vertical takeoff, and their wing never "stands parallel to the ground" during takeoff!

When gliding an airplane or a bird, as well as during an “idle”, the most economical horizontal flapping flight at a gliding speed with good aerodynamics of the entire wing system, its drag turns into the necessary lift for such a flight, it is for this reason that when some parameters are changed in flapping mode, the flight speed can be even lower than when planning. It depends on the possibility in this mode to keep the air on the bearing surface of the wings without flow stall.
It is clear that such a flywheel will not be able to hang like a dragonfly in one place, but it is quite suitable for an economical horizontal flight.

If the path for the time is the speed, then the wing, moving along a sinusoid in the process of flapping, covers a greater distance in the same time than the body of the bird. And since the wing travels a longer distance in the same time, it means that the speed of the wing in the air flow around it has become greater and, accordingly, its lifting force has increased!

To understand how the wing behaves in the “idle”, the most economical mode of flight of a calmly flying bird, it is enough to take a plywood sheet, approximately 100 x 50 cm, by the narrow edge in an outstretched hand against the wind, as if it were your wing, and alternately changing the angle attack try to keep it horizontal to the ground.

With a good wind, it will hardly be possible to keep your hand in a horizontal position, but you will get practically oscillatory, waving movements! Here is a special case of parametric resonance! And if you fix a five-meter relatively thin but strong board in the rear windows of the car and at different speeds, leaning out of the window with a bracket, try to bend it transversely a meter from the window, changing the angle of attack in time with your own oscillations, what will you get? The same waving movements, only with a more elastic oscillatory system. If one end of the board in the window is rigidly fixed, and in the other window the board is fixed in a spring suspension with dynamometric devices, then even on a board without a special profile, you can see a sharp decrease in the weight of the board under different modes of its oscillation. Can you guess how such a board with an airfoil wing would work? By the way, at a certain speed, critical modes may appear and the board will break...

Birds do this in an oncoming flow at a gliding speed, but they fly WITHOUT DECREASE, since in this case the wing retains its lift at each moment of the stroke, having the necessary angle of attack and sufficient speed for this in this oncoming air flow, because the wing passes along the sinusoid bigger way than a bird's body!

When a seagull in a gliding flight begins to change the angle of attack of the wings, it receives the necessary oscillations on the wings for a stable horizontal flight!

This is due to the fact that her wings travel a longer path along the sinusoid than her body, which moves in a straight line, and the path for a while is speed, which means that the speed of the wing has become greater from this and the lift on the wings has increased compared to flying without flapping and the bird flies without a decrease, almost without spending its energy on the flight due to the high quality of the wing and the almost complete absence of drag! But the speed both in a gliding flight and in a flapping one is the SAME! And also without drag!

But when a bird needs to fly faster, it can to some extent change both the frequency, and the effort for flapping, and the amplitude of flapping, creating a propelling effect on the wings due to the elasticity of the feathers and the transverse elasticity of the wing structure!

By the way, in this case, both frontal resistance and air resistance appear, which already requires considerable effort, and hence significant energy costs. This is about the same as walking at a calm pace, and then running fast. By the way, when walking and running, a person’s legs also work as an oscillatory system and also in the parametric resonance mode, if someone still didn’t know this ...

And the muscles, both during the flight of birds and insects, and when a person walks, only swing the pendulum and GIVE pumping energy to set the oscillatory system in motion to perform the necessary work!

In the flywheel seat in the hands of the pilot, the handles for GAUCHING the wing and by changing the angle of attack to the resonance of the oscillation of the wings, and even swinging the wings with your legs, you can get enough lift and thrust for horizontal flight!

By the way, the albatross has a special bone in the shoulder joint to reduce the energy spent on keeping the wings in the extended state, which, with the wings extended, enters the groove of the shoulder bone, which makes the wing more rigid and elastic. This allows him to spend less energy on keeping the wings in the extended state, expending them only on steering to maintain flight and maneuver.

And on the wings of a dragonfly there is a chitinous seal, which is called pterostigma, if this seal is carefully cut off, then the oscillation frequency of the wings increases and the wing begins to collapse, because the natural oscillation frequency of the wing and the frequency of the muscles that control the wings no longer coincide, and this imbalance leads to the destruction of the entire balanced system necessary for its full, stable and safe flight.

In my opinion, everything is elementary simple and clear ...

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Thank you for reading and indifference!!!

In this book, a schoolboy and a young naturalist will find material for extracurricular reading, as well as additional and reference material for a zoology textbook.

Individual essays are not linked, so it is not necessary to read the entire book in a row.

The book introduces the reader to the diversity of the animal world of the USSR and foreign countries. Along the way, information is given about the importance of animals in nature, human economic activity.

Part of the material is presented in the form of questions and answers. The section "Stories about insects" was written by the candidate of biological sciences Yu. M. Zalessky.

In the third edition, the text has been changed and supplemented in places; Necessary corrections have been made, several new drawings have been added. The chapter "Zoology in questions and answers" is supplemented with new questions; the order of their distribution has been changed in accordance with the zoological system.

J. Zinger

Book:

How insects fly

Most of the insects that inhabit the Earth have wings. True, only insects in the adult stages of development have wings. As you know, neither larvae, nor nymphs, nor pupae fly. Some insects, such as dragonflies, butterflies, hymenoptera, beetles, have four wings, while others: flies, mosquitoes, some mayflies, have two wings. Each insect has its own characteristics of flight, each flies in its own way, but many of them have something in common in flight. First of all, their flight is based on flapping wings - flapping flight.

The most simple flap of wings is possessed by mayflies- they flap each wing from top to bottom and only slightly place it at an angle to the oncoming air flow. The most complex wing flap is possessed by Diptera(mosquitoes and flies) and hymenoptera(bees, wasps, winged ants). Their wings flap so that the end of each wing, if the insect is motionless, describes a figure-of-eight curve in the air. Waving down, the wing at the beginning of the stroke is located almost horizontally. Going down, it simultaneously moves forward, and at the bottom it turns over so that, rising up, it already goes up and back with its front edge. Such strokes are repeated with great frequency. Each wing works like a propeller.

The arrows indicate the direction of movement: A - lowering the wing (V position is shown by a dotted line); B - raising the wing (position I is shown by a dotted line).

Below - the same position of the wing on the sinusoid. The dot is the leading edge of the wing, the dash is the wing plate.

Such a figure eight can only be observed in an immovably fixed insect when it flaps its wings. When flying, when the insect moves forward, this figure eight stretches and the end of the wing describes a wavy curve (sinusoid).

Hymenoptera have four wings, but the forewings and hindwings of each side of the body are connected in flight by a hook-like hook, so that the right and left pairs of wings act together as one wing.

Flight control in insects is achieved almost exclusively by the wings. A change in the direction of the flapping plane affects the change in the direction of flight. This achieves a change in flight to translational movement forward, backward, flying in one place or hovering in the air (“standing” flight), lifting up, turning right and left. Flies are one of the most agile insects in flight. They often make sharp jumps to the side. This is achieved by suddenly turning off the wings of one side of the body - their movement stops for a moment, while the wings of the other side of the body continue to oscillate, which causes a jump away from the original direction of flight.

Bees in flight." class="img-responsive img-thumbnail">
Bees in flight.

Insects such as mayflies can also change the direction of flight and steer slightly by changing the position of the abdomen and the tail filaments located at its end.

Insects, flying, very often flap their wings, so often that individual wing beats cannot be seen by the human eye. We can often hear a bee or a beetle buzzing in flight. What does this buzzing mean?

Sound is vibrations in the air that we pick up with our ears. The more frequent the air vibrations, the higher the pitch of the sound. The dung beetle makes up to 87 wing beats per second, the sound that occurs in this case is a buzzing of a relatively low tone. A mosquito, flying, produces up to 594 flaps per second with its wings, which is why the sound resulting from its flight is so high and resembles a squeak.

The frequency of wing beats can be determined by the pitch of the sound they produce. It is only necessary to take into account that the highest note corresponds to twice the number of oscillations per second, since each stroke of the wing gives two waves of air oscillations.

So, for example, at honey bee a high note corresponds to 440 double vibrations per second, i.e. 220 strokes per second. And indeed, as observations show, the bee makes an average of about 260 strokes per second.

Different insects, when flying, flap their wings at different frequencies, and in dipterans and butterflies, the number of flaps increases with increasing air temperature, while in hymenoptera and beetles, the frequency of wing flaps does not depend on temperature. Butterflies rarely flap their wings. The machaon makes 5 strokes per second, the rutabaga makes 6, and the mourning woman makes 10 strokes per second. At a distance of half a meter, the flight of butterflies seems completely silent, but if a diurnal butterfly flies by the very ear, then you can hear the sound of a very low tone produced by its wings. Night butterflies usually flap their wings more frequently. scoops(genus agrotis) make 37-48 strokes per second, and ocellated hawk hawk- 37–41 swing.

Moth hawks, especially small tongues, produce a low buzz, slightly reminiscent of the buzz of a bumblebee.

Above - a noticeable wave running through the wings (according to filming). Below - a "standing" flight of hawk moth sucking nectar.

The bumblebee makes 123 to 233 strokes per second, and the common wasp 165–247. The housefly makes 147-220 strokes per second. However, twitch mosquitoes flap their wings most of all, sometimes pushing in swarms in the air. Their larvae are often fed to aquarium fish - this is the so-called bloodworm, bright red mobile worms. Their fishermen put on a fishing hook, using as bait for fishing.

The shaggy mustache twitch makes from 196 to 494 strokes per second, and other representatives of this large family of twitchers even produce up to a thousand strokes per second.

How much energy do insects need to expend to fly when flapping their wings at such a frequency! How often their muscles contract! However, experiments have shown that a bee, flying for a bribe at a distance of 3 kilometers, consumes only 0.00035 grams of sugar. The goiter of a bee usually contains 0.02 grams of nectar. With a concentration of sugar in it at 20 percent, this amount is equal to 0.004 grams of pure sugar. Therefore, even at a distance of 3 kilometers, the flight of a bee is quite profitable, since the consumption of burning food in the form of sugar does not exceed 9 percent of the load.

If we take bees or bumblebees and put them in an insectarium or a large glass jar covered with gauze on top, then in 2–2.5 hours they will die of hunger, because, flying, they will use up all their strength and the entire supply of food. If we put them in a cramped box with holes where they cannot fly, the insects will live much longer and retain the ability to fly.

If at the first experiment we feed them, they will not die for a long time. Flight requires a large expenditure of energy from the insect.

There is a movie camera (“a magnifying glass of time”) with which you can take snapshots at a very high speed. If you shoot flying insects at a speed of 2000 or 3500 frames per second, and then view the filmed film on the screen at a speed of 16 frames per second, that is, 125 and 219 times slower, respectively, then you can see all the movements of the wings of insects and consider how they fly.

It turns out that the flight of butterflies, especially diurnal ones, is very different from the flight of other insects. The right and left pairs of their wings, when flapping, approach each other above and below the body. Over the back, the wings even often meet completely and sometimes strike each other, making a sound. The wings of the right and left sides flap at the same time, since the front and rear are connected to each other and usually have a special hold for this purpose. When approaching, the wings first touch with their front edges, and then with the entire plane. Due to this, the wings, as it were, squeeze out the air between them. The same happens when the wings meet under the body with a downward stroke. In addition, when watching a high-speed film in such a slow motion, you can see how the wings of butterflies smoothly bend, a wave runs through their wings from the front edge to the back, and they seem to float, slowly moving their wings.

A - admiral; B - urticaria.

Dragonfly uses a variety of techniques in flight; then it flaps its front and rear wings alternately, then it suddenly switches to a gliding flight on outstretched fixed wings, then it flaps its wings again, but this time both front and rear wings at once. There have been cases when a dragonfly flapped one front pair of wings, keeping the back pair calmly extended. You can often see how a dragonfly hangs motionless in the air, as if “standing”, flapping its wings in one place. The dragonfly can also move in flight not only forward, but also backward, and, pursuing elusive prey (small insects), it can soar up a short distance almost vertically.

Aerodynamicists know a phenomenon called flutter. These are harmful vibrations of the wing in flight, which in high-speed aircraft can reach dangerous sizes, so that the wings even break. Technicians have long been looking for ways to offset these harmful fluctuations. Models of the new test aircraft died, test pilots also died, but the designers could not find the right solution to the problem for a long time. Finally, the problem was solved: the anti-flutter device was found. A weight was made at the leading edge at the end of each wing (in the simplest case, a lead weight was soldered) - it damped harmful vibrations.

The flapping flight of insects, and in particular the flight of dragonflies, also has harmful vibrations. Nature over the centuries has developed devices to combat flutter. This adaptation is clearly expressed in most dragonflies. On each wing, in its apical part, near the anterior margin, there is a dark chitinous thickening - pterostigma, or wing eye. Removing this eye, without depriving the dragonfly of the ability to fly, violates the regularity of wing oscillations, the dragonfly begins to flutter, as it were. Experiments have shown the mechanical significance of these formations, which regulate the oscillations of the wing. The peephole turned out to be a device that saves the flapping wing from harmful flutter-type vibrations. If this meaning of the wing eye in dragonflies had been known before technicians had invented the anti-flutter device in airplanes, then by borrowing it from insects, a long search could have been avoided.

In beetles, when not flying, the front rigid wings, or elytra, cover and protect the folded back membranous wings. Beetles almost never use elytra in flight; the elytra only sway slightly in time with the beat of the hind wings. In flight, the elytra are held at a certain angle to each other - in the form of the Latin letter V. This ensures the lateral stability of the beetles in flight, just as the V-shaped raised wings of an aircraft ensure its stability when turning. When an airplane turns, it rolls over and rests on one wing while the other rises. The air rushing onto the wing presses on its surface and returns to its previous position, straightening the aircraft.

Beetles from the family bronzovok fly with folded elytra, exposing membranous wings from under them. The flight of bronzes has great maneuverability.

Have the highest flight speed hawk moths And horseflies: they develop a speed of 14 to 15 meters per second. Dragonflies fly at a speed of 10 meters per second, dung beetles - up to 7 meters per second, May beetles - up to 3 meters per second, bees - up to 6.7 meters per second.

Once they observed how a large dragonfly did not lag behind an airplane flying at a speed of 144 kilometers per hour, and at times even overtook it.

The flight speed of insects is slow compared to birds. If a bumblebee makes 18 kilometers per hour, then a crow - 50 kilometers, a starling - 70, and a swift - 100 kilometers. The record speed of a propeller-driven aircraft is 900 kilometers per hour.

However, if we calculate the speed with which a bumblebee, a swift, a starling, a crow and an airplane move forward at a distance equal to the length of their own body, then it turns out that the relative speed will be the least for an airplane and the most for insects.

Birds. The wing should be considered the most important morphological adaptation to the air environment.

Wing- this is the bearing plane, which is formed by flight feathers. On the fingers and wrists there are 11 flight feathers of the 1st order, and on the forearm - 12 flight feathers of the 2nd order. The basis of the flight feathers is a rigid rod, to which the beards that make up the fan are attached symmetrically on both sides.

In order for the wing to generate lift, the bird must gain a starting speed. Then the air flow is distributed relative to the plane of the wing in such a way that an increased air pressure is created under the wing. Above the upper surface of the wing, the air moves faster, resulting in a relative rarefaction. A lifting force arises, which the bird manipulates by changing the angle of attack, wing area, and braking with tail feathers.

The speed of movement in the air is maintained in various ways. Different birds develop different speeds in the air. It depends on the size and shape of the wing, the ability of the bird to change the shape of the wing during flight, the frequency of wing beats, and the ability of the bird to use the energy of air currents. It is customary to distinguish several types of flight: waving, gliding (soaring), hovering flight.

flapping flight suggests that the bird has short and moderately wide wings and well-developed pectoral muscles, as, for example, in a pigeon. The mass of pectoral muscles which can reach 30-40% of body weight. The frequency of wing beats in a pigeon is approximately 2 flaps per 1 second, in larger birds it is less common. Birds use the tail and partly the wings as a brake.

The plumage of a bird plays an important role in the organization of flight. It gives the body a streamlined, absorbs the influence of air currents. When pushing, the flight feathers are closed due to the adhesion of hooks and grooves and form a relatively rigid bearing plane of the wing. When the wing rises, the feathers open, resulting in a sharp decrease in air resistance. When landing, the bird stops flapping its wings, holding them at the required angle.

In the final part, tail feathers and primary wing feathers are used as a brake, which turn their ventral surface almost perpendicular to the direction of movement.

Gliding flight. During gliding flight, birds use the energy of the movement of air currents. Birds have a large wing area either due to length (frigate), or due to length and width (eagles). When planning a bird, the wing takes on the maximum length and is set within the plane of motion at an angle of 90 ° relative to the longitudinal axis of the body. When gliding, the birds move without losing altitude or even gain altitude with minimal energy expenditure. The reduction during soaring is also possible without additional energy costs due to downward air currents.

Birds such as eagles, kites, and to a lesser extent crows use the energy of ascending and descending air currents when planning. The surface of the earth warms up and cools unevenly. Warmer air is displaced by colder air, resulting in a vertical movement of air masses. In addition, there are air movements in the horizontal plane. In mountainous areas, horizontally moving air currents hit an obstacle (mountain slope) and rise up.

In sea birds (albatrosses, frigates), the flight is somewhat different from the gliding flight of birds living on land.

They have long and narrow wings (in the frigate and albatross up to 4 m) with a rather large body. Birds take advantage of the gusts of wind that rise above the waves. Using oncoming air currents, birds gain height. Then they turn 180 ° and at high speed glide downwind on wings bent back, losing height in the process. This is followed by a turn in a wide arc with wings extended forward towards the air flow. Similar maneuvers are also available to land birds. But the albatross also periodically soars above the waves due to air currents rising from the surface of the water in the same way as land birds do.

hovering flight. This type of movement in the air seems to be the most energy intensive. In order to stay in place and not lose altitude, the birds must simultaneously create a large lift and dampen the linear advance by braking. In a hovering flight, birds flap their wings at a high frequency (about 50 beats per second). In such birds (kestrels, hummingbirds), the muscles that set the wing in motion have a very large mass. Only the pectoral muscles can have a mass that is 1/3 of the total body weight. Thrust is created by the work of a light and very mobile wing, which is dominated by long and relatively stiff primary feathers of the 1st order. Flight feathers of the 2nd order in birds using hovering flight are not 12, but only 6.

mammals. Locomotion in the air in mammals is a rare phenomenon. Bats are the most adapted to flight. These animals move unsteadily on the ground (more precisely, along the vertical surfaces of trees, caves), but masterfully move in the air. Some species (for example, long-winged) develop speeds of up to 35-40 km / h in flight at short distances.

Bats, or bats (Chiroptera), have a large flying membrane. It is a fold of skin between the forelimbs, trunk and hind limbs, as well as between the toes of the forelimbs, trunk and tail. The hypertrophied pectoral muscles and forelimbs set in motion the flying membrane. Among bats, depending on the structure of the flying membranes, sharp-winged, long-winged, broad-winged and blunt-winged bats are distinguished. The biomechanics of the movements of bats in the air does not fundamentally differ from that of birds.

In bats, the same three types of flight can be observed as in birds: flapping, hovering (fluttering) and gliding.

In addition to bats, locomotion in the air is available to flying squirrels, monkeys, and some other small animals that lead an arboreal lifestyle. Among the squirrels that use the air for linear movement, the most famous are the northern flying squirrel and the giant flying squirrel. The latter, despite its considerable size (body length 40-50 cm, tail length up to 60 cm), although it is not able to fly for real, nevertheless, due to planning, it covers distances up to 500 m. At the same time, the squirrel moves from one high tree to another. Due to such locomotions, the rodent avoids dangerous neighbors on the ground and changes its feeding grounds without descending to the ground. From the heels to the wrists of the flying squirrels, wide membranes stretch along the body, which, when jumping, create a bearing plane with a rather large surface.

The northern flying squirrel is smaller. The length of its body does not exceed 25 cm, the tail is 18 cm. However, this squirrel easily flies from tree to tree at a low speed of about 100 m / min. Despite the fact that such a flight has a passive character, nevertheless, it allows squirrels to solve life problems: to get away from predators, find sexual partners and develop new food resources.

Fishes. The flight of fish is even rarer than the flight of mammals. However, its effectiveness can be comparable to the flight of birds.

Fish use their pectoral fins to glide in the air. So, flying fish, when frightened, due to the throwing movement of the trunk muscles, the muscles of the caudal peduncle and the intensive work of the lower lobe of the caudal fin, jump out of the water and fly distances in the air, allowing them to get rid of their pursuers.

On the surface of the water, a flying fish works with its tail for quite a long time, developing great traction, which allows it to overcome the force of gravity. The flight speed of these small fish exceeds the speed of the pursuers (tuna, swordfish), and the distances they fly reach several hundred meters.

Other types of fish, such as fingerwings, can not only soar, but also perform complex maneuvers in the air. The finger wing rises to the surface of the water and slides over it at a speed of 18 m/s. The fish acquires such a high speed due to the zigzag movements of the caudal fin with a hypertrophied lower lobe.

The flight speed of the fingerwing is comparable to the speed of modern sea vessels and is often 60-70 km/h. A strong blow of the tail lifts the fish into the air to a height of 5-7 m. The finger wing flies in the air up to 200 m, using air currents as well. The fish is able, if necessary, to change the direction of flight due to the movements of the tail fin. She also has oscillatory movements of her pectoral fins.

Lesson on the topic
"The reason and significance of warm-blooded birds"

When studying the topic “Bird Class”, the guys for the first time get acquainted with such an important concept as warm-bloodedness. It is very important that students understand that the maintenance of a constant body temperature is ensured by the interaction of a number of physiological systems of the body. A good knowledge of this material is necessary to explain complex evolutionary and ecological problems.

Teacher.

- Guys, why are there fewer birds in the forest in winter than in summer?
(Suggested answers: little or no food(for insectivorous birds), a lot of snow, cold.)
- Can a feather cover protect birds from frost in winter? ( Maybe, but only partially.)
The main questions that we must answer during today's lesson are: what warms the bird's body? How do they maintain a constant temperature? Where does the energy for flight come from?
How is heat generated in general? ( Suggested answers: in the combustion of organic matter, which occurs in the presence of oxygen.)
- What drives the car? What makes organisms move? ( Due to the energy generated during combustion(oxidation)organic matter with the participation of oxygen.)
How much energy do birds need? After all, they can fly long distances, develop high speed. (Working with tables.)

Table 1. Distances traveled during flights

Table 2. Surface area of ​​the wings and the load on them

For comparison, the glider model has a wing load of 2.5 kg / m 2.

Table 3. Wing beat frequency

Table 4. Maximum flight speed

The smaller the bird, the more food for every gram of body weight it needs. As the size of the animal decreases, its mass decreases faster than the surface area of ​​the body through which heat is lost. Therefore, small animals lose more heat than large ones. Small birds eat an amount of food per day equal to 20–30% of their own weight, large birds - 2–5%. A titmouse can eat as many insects in a day as it weighs itself, and a tiny hummingbird can drink an amount of nectar that is 4-6 times its own weight.

Repeating the stages of splitting food and the features of the respiratory system of birds, we fill in the scheme No. 1 in stages.

The progress of work when filling out the scheme

Intense motor activity of birds requires a lot of energy. In this regard, their digestive system has a number of features aimed at the efficient processing of food. The beak serves as an organ for capturing and holding food. The esophagus is long, in most birds it has a pocket-like extension - goiter, where food softens under the influence of goiter fluid. The glandular stomach has glands in its wall that secrete gastric juice.
The muscular stomach is equipped with strong muscles and is lined from the inside with a strong cuticle. In it, mechanical grinding of food takes place. Digestive glands (liver, pancreas) actively secrete digestive enzymes into the intestinal cavity. The split nutrients are absorbed into the blood and carried to all cells of the bird's body.
How long does it take for birds to digest food? Small owls (house owls) digest a mouse in 4 hours, a gray shrike - in 3 hours. Juicy berries in passerines pass through the intestines in 8–10 minutes. Insectivorous birds fill their stomach 5-6 times a day, granivorous birds - three times.
However, in itself, the absorption of food and the entry of nutrients into the blood is not the release of energy. Nutrients need to be "burned" in tissue cells. What system is involved in this? ( Lightweight, air sacs.)
Muscles must be well supplied with oxygen. However, birds cannot ensure the delivery of the required amount of oxygen due to the large amount of blood. Why? ( An increase in the amount of blood would increase the mass of the bird and make it difficult to fly.)
An intensive supply of oxygen to tissue cells in birds occurs due to “double breathing”: oxygen-rich air passes through the lungs both during inhalation and exhalation, and in the same direction. This is provided by a system of air sacs penetrating the bird's body.
In order for the blood to move faster, you need high blood pressure. Indeed, birds are hypertensive. In order to create high blood pressure, the heart of birds must contract with great force and high frequency (Table 5).

Table 5. Heart weight and heart rate

As a result of the oxidation (combustion) of nutrients, energy is generated. What is she spending on? (We are finishing filling out scheme No. 1).

Output. An active oxidative process helps maintain a constant body temperature.
High body temperature provides a high metabolic rate, rapid contraction of the heart muscle and skeletal muscles, which is necessary for flight. High body temperature allows birds to shorten the period of development of the embryo in the hatching egg. After all, incubation is an important and dangerous period in the life of birds.
But constant body temperature has its drawbacks. Which? We fill out the scheme number 2.

So, maintaining a constantly high body temperature is beneficial for the body. But for this it is necessary to consume a lot of food, which must be obtained somewhere. Birds had to develop various adaptations and behaviors to get enough food. Here are some examples.
Next, students make reports on the topic “How different birds get their own food” (their preparation could be homework for this lesson).

Fishing Pelicans

Pelicans sometimes fish together. They will find a shallow bay, cordon it off in a semicircle and begin to flap the water with their wings and beaks, gradually narrowing the arc and approaching the shore. And only after driving the fish to the shore, they start fishing.

Owl hunting

Owls are known to hunt at night. The eyes of these birds are huge, with a greatly expanding pupil. Through such a pupil and with poor lighting, enough light enters. However, it is impossible to see prey - various small rodents, mice and voles - from afar in the dark. Therefore, the owl flies low above the ground and looks not to the sides, but straight down. But if you fly low, the rustling of the wings will scare away the prey! Therefore, the owl has soft and loose plumage, which makes its flight completely silent. However, the main means of orientation in nocturnal owls is not sight, but hearing. With its help, the owl learns about the presence of rodents by squeaking and rustling and accurately determines the location of the prey.

Armed with stone

In Africa, in the Serengeti reserve, biologists have observed how vultures got their food. This time the food was ostrich eggs. To get to the delicacy, the bird took a stone with its beak and threw it with force at the egg. The strong shell, which could withstand the blows of the beak of even such large birds as vultures, cracked from the stone, and one could feast on the egg.
True, the vulture was immediately pushed back from the feast by vultures, and he was taken for a new egg. This most interesting behavior was then repeatedly noted in the experiment. Eggs were tossed to the vultures and expected to happen. Noticing the delicacy, the bird immediately picked up a suitable stone, sometimes weighing up to 300 g. The vulture dragged it in its beak for tens of meters and threw it at the egg until it cracked.
Once a vulture was given fake chicken eggs. He took one of them and started throwing it on the ground. Then he took the egg to a large rock and threw it against it! When this did not bring the desired result, the vulture began to desperately beat one egg against another.
Numerous observations have shown that the birds tried to split any egg-shaped object with stones, even if it was huge or painted in unusual colors - green or red. But they did not pay attention to the white cube at all. Scientists have found, in addition, that young vultures do not know how to break eggs and learn this from older birds.

osprey fisherman

The osprey is an excellent angler. Seeing the fish, it quickly rushes into the water and plunges its long sharp claws into the body of the victim. And no matter how the fish tries to escape from the claws of the predator, it almost never succeeds. Some observers note that the bird holds the caught fish with its head in the direction of flight. Perhaps this is an accident, but it is more likely that the osprey is trying to catch fish in such a way that later it would be easier to carry it. Indeed, in this case, air resistance is less.

Conclusion from student reports - the progressive development of the brain and the leading sense organs (vision, hearing) is associated with intensive metabolism, high mobility and complex relationships with environmental conditions.
Now explain why birds have become widespread in all climatic zones. What is bird flight? ( Warm-bloodedness allows birds not to be afraid of frost, to remain active even at very low ambient temperatures. However, the lack of food in winter forces them to migrate to more nutritious places.)