Why birds fly and not fall? Why does the force of gravity does not prevent them to rise into the air?
Birds have many adaptations for flight. First of all, it is
The wing is designed so that creates a force opposing the force of gravity. Because of the bird's wing is not flat as a Board, and curved. This means that the jet of air, the envelope of the wing, must pass through the upper side of the longer path than on the concave bottom. Both the air flow has reached the tip of the wing at the same time, the airflow over the wing must move faster than under the wing. Therefore, the flow rate of air over the wing increases and the pressure decreases.
The pressure under the wing and above it creates a lifting force directed upwards and counteracting the force of gravity.
Feathers is a complex but very light keratotic skin lesions. They were transformed in the process of evolution from ancient scales of reptiles. The feathers make the surface of the body of the bird is smooth, and when it is in flight, the air without great resistance to wrap around her torso. Because feathers are lifting force and thrust. In addition, with their help, the bird adjusts the direction of flight (tail feathers of the tail). Heat-retaining elastic springy and very strong, they form a uniform layer, which protects birds from possible harmful effects of the environment - excessive heat, cold, moisture and wind, and prevent loss of heat.
3. Body shape
The body shape of birds - streamlined, largely due to the feathers.
4. Skeletal features
Only birds on the outer surface of the sternum has a large growth - Kiel. To it are attached the chest muscles that move the wings.
- The skeleton of birds is very hard due to the accretion of bones with each other. For example, in the spine of the individual vertebrae are firmly fused to each other and do not form a movable, flexible chain, as in the skeleton of mammals. And lumbar vertebrae to create a good support coalesced with each other, with the sacral and tail vertebrae, as well as with the iliac bones.
- The skeleton of birds is very easy, as a number of bones contains pneumatic cavities. In the bones of birds are not red bone marrow.
25% of the mass of birds make up the pectoral muscles, which raise the wings. These muscles are attached to the keel - the growth of the sternum (see above). Creating an optimal body shape large muscles that move the limbs, are located on the body, and the limbs are tendons. So the birds legs are thin.
Muscles birds stock a lot of oxygen due to the high protein content of myoglobin.
6. Dual breath
Inhaled bird of the air moving through the tubes and bronchioles in the lungs and into the air bags. When you exhale it goes from bags again on the tubes through the lungs, where gas exchange is happening again. This dual breath increases the supply of oxygen, which is very important during the flight.
7. Features of the cardiovascular system and metabolism
The heart of larger birds than in mammals of similar body size. The smaller the type, the more his heart. All the birds who fly frequently, the heart has to be large to ensure a quick blood circulation.
The frequency of heart contractions correlated with its size. Heart rate in birds up to 1000 beats per minute, while they have a very high pressure (180 mm Hg, and we mammals - only 100-120).
The blood of birds contains more red blood cells than most mammals, and as a result, in a time unit can carry more oxygen, which is necessary for flight.
Due to well-developed circulatory and respiratory systems of birds are very fast metabolism and high body temperature. Compare: in mammals from 36 to 39°C, and the birds - from 40 to 42°C. At high temperatures faster are all vital processes, including faster the muscle contraction. This allows the birds to do more work per unit of time.
And to obtain large amounts of energy birds need more food than mammals of the same body weight. I understand now why it is so important to feed birds in the winter when natural food for them becomes a little?
8. Nervous system
Birds powerful cerebellum, because this body is responsible for coordination needed in flight.