Most representatives of the class of birds have mastered the ground-air habitat. The adaptation of birds to flight is due to the peculiarities of their external and internal structure. In this article, we will consider these aspects in more detail.
Signs of adaptation of birds to flight
The main features that allow birds to master the air environment are:
- feather cover;
- modification of the forelimbs into wings;
- warm-bloodedness;
- light skeleton;
- the presence of a special bone - the keel;
- double breath;
- shortened intestine;
- absence of one ovary in females;
- well developed nervous system.
These structural features illustrate how birds are adapted to flight.
Skeleton structure
It becomes possible for birds to climb up with ease, first of all, thanks to their light skeleton. It is formed by bones, inside of which there are air cavities. The main divisions of the bird skeleton are the skull, spine, belts.upper and lower limbs and the free limbs themselves. Many bones fuse together, providing strength to the entire "construction". A distinctive feature of the feathered skeleton is the presence of a keel. This is a special bone to which the muscles that set the wings in motion are attached. It is characteristic only for birds.
Sheaths
Features of birds' adaptation to flight are largely related to the characteristics of the covers. Feathers are the only group of animals whose body is covered with feathers. They can be grouped into three groups. The first is called "contour". Thanks to them, the body of the bird acquires a streamlined shape. Depending on the location on the body and the functions performed, the contour wings are covering, fly and steering. They cover the body, forming the contours of the wings and tail. Regardless of the type, each wing consists of a central part - a rod, on most of which there are fans formed by barbs of the first and second order with hooks. The lower bare area of the feather is called the chin.
The second group is represented by down feathers. Their beards are devoid of hooks, so the fans are not linked, but free. The third variety is fluff. A characteristic feature of its structure are fluffy beards, which are located in a tuft at one end of a strongly shortened head.
On the example of the features of plumage, it is easy to see how birds have adapted to flight. It provides thermoregulation, determinescoloring, the ability to move in the airspace. By the way, the color of birds can serve both as a disguise from predators, and as one of the forms of demonstrative behavior.
Warm-blooded
This adaptation of birds to flight is very important. Warm-bloodedness implies the presence of a constant body temperature, independent of the environment. After all, as you know, with height, the air temperature decreases significantly. And if the birds were cold-blooded, like fish or amphibians, they would simply freeze during the flight. This feature is inherent in this group of organisms due to the progressive structure of the circulatory system. It is represented by a four-chambered heart and two circles of blood circulation. Therefore, venous and arterial blood do not mix, the exchange of gases and substances occurs very intensively.
Exterior structure
The body of birds is divided into the following parts: head, movable neck, torso, tail and limbs. On the head are eyes, nostrils and a beak covered with horn covers. The lack of teeth makes the skull even lighter. The eyelids of the eyes are motionless, the cornea is moistened with the help of nictitating membranes.
The main adaptation of birds to flight, of course, lies in the modification of the upper limbs. They are transformed into wings. Legs - lower limbs, often covered with horny scales. This feature of the structure remained in birds from their ancestors - reptiles. The claws on the toes help the birds to stay on the supporting surface.
Internal structure of birds
Adaptation of birds to flight is also reflected in the structural features of most internal organs.
The digestive system is represented by the oral cavity, the esophagus, which forms an extension - goiter. In it, the food undergoes additional enzymatic processing, becomes soft and digested faster. Further, food enters the stomach, which consists of two sections: glandular and muscular, and then into the intestines. It opens outwards with a cloaca. The intestines of birds are shortened compared to other animals. This structure also makes their body lighter. Undigested food remains do not stay long in the intestines and can be excreted through the cloaca even during the flight.
Adaptation of birds to flight can be traced in the structure of the nervous system. Thanks to its development, animals have fairly clear color vision, which makes it easy to navigate in the air even at a fairly high altitude. Hearing functions well. And thanks to the developed cerebellum, coordination of movements is also at a high level. Birds react quickly during an approaching danger or hunting.
Compactness is a characteristic feature of the reproductive system. The testicles of males are small, bean-shaped. They open their ducts directly into the cloaca. Females have only one ovary. This structure makes the weight of the birds significantly less. The egg from the gonad moves along the oviduct, where the fertilization process takes place, the egg is covered with shells and calcareous shells. Further through the cloacacoming out.
Features of breathing
Adaptation of birds to flight also applies to the respiratory system. Indeed, for the intensive work of the muscular system, a continuous supply of tissues and organs with oxygen is necessary. Therefore, along with pulmonary respiration, birds have additional organs - air sacs. These are additional air reservoirs with a sufficiently large volume. Therefore, the breath of birds is also called double.
Adaptation of birds to their environment
The features of the external structure often change depending on the habitat. For example, a woodpecker living in the forest has sharp claws. With their help, he moves along the branches of trees, leaning on a tail with hard feathers. The beak of this bird is like a chisel. Using it, as well as with the help of a long sticky tongue, he gets insects and larvae from the bark, seeds from cones.
Birds - inhabitants of water bodies, also have a number of important adaptations. These are short lower limbs with swimming membranes, a dense feather cover, lubricated with a water-repellent secretion of special glands. "Get out of the water dry" - this proverb, known to everyone, appeared due to the peculiarities of the life of waterfowl.
Inhabitants of open spaces - steppes and deserts, have protective coloration of feathers, very powerful legs and excellent eyesight.
Birds of the coast are masters of gliding. Albatrosses, gulls and petrels are characterized by strong and long wings. But they have a short tail. All this allows coastal inhabitants to fish directly fromair.
Is it possible to see prey at a distance of up to a thousand meters? For birds of prey, this is not a big deal. Falcon, hawk, eagle are bright representatives of this group. They have a large curved beak with which they grab and tear food. And powerful sharp claws leave no chance of salvation. Predators are able to soar in the air for a long time thanks to their very wide wings. And those of them who hunt at night, additionally have sharp eyesight and perfect hearing. For example, owls and owls.
Do all birds fly
Not all members of this class are able to fly. For example, penguins are excellent swimmers, their upper limbs are modified into flippers. But these birds cannot fly. They have a keel, but their large weight does not allow them to soar into the air. A thick fat layer and dense plumage are simply necessary for life in the harsh conditions of the north.
Ostrich superorder unites emu, kiwi, cassowary, rhea. These feathered keels are absent. And the inability to fly is compensated by a fast run. This skill saves birds in flat African conditions.
The vast majority of modern birds are perfectly adapted to flight and habitat. They live in the forest, on water bodies and their coasts, steppes and deserts.
Representatives of the bird class are striking in their diversity, are important in nature and human life, and the characteristic features of the structure determine the ability to fly.
