Birds - the only group of vertebrates, except for bats who are capable to fly, but not just to soar on air flows. This ability is received by them as a result of evolutionary changes of a skeleton.
Birds – surprising creations. The nature granted to most of them ability to use all three elements – both air, and the earth, and water. This ability is caused by features of the structure of a skeleton and muscles of birds, existence of a pen-type covering.
What does the skeleton of birds differ from skeletons of other living beings in in what its feature?
Features of the structure of a skeleton of birds
Birds were the first warm-blooded animals on Earth. There was this look from reptiles, today in it there are 40 groups which, in turn, consist more than of 200 families.
The feature in the structure of a skeleton of birds is that in it the fitness to flights is pronounced. It consists of thin, flat and spongy bones. Cavities in them are filled with either air, or marrow, depending on what functions they perform.
During archeological excavations the scientists find skeletons of representatives of this class of animals which perfectly remained, and explain their durability and resistance to external destroyers with their building.
The skeleton of any bird is divided into several so-called belts, each of which performs certain functions and bears a certain loading. Thanks to the fact that loading is distributed correctly birds also are capable to fly, but not just to soar on air flows. Many of them can fly against wind, and quite strong.
Besides, the skeleton answers and for safety of an individual – its cervical department is extraordinary mobile, the head of the majority of birds can turn instantly at once on 180 ˚. It helps not only to trace space around and in time to notice danger, but also it is productive to hunt.
Evolutionary changes of a skeleton of birds
Birds originate in a branch of archosaurs which does not exist today any more, that is they remained her only representatives. Archosaurs were an intermediate link between reptiles and birds. The shortened front extremities and extended back as well as at modern representatives of a class of birds were characteristic of their skeleton. The main and only difference – the archosaur still had a long tail. Front extremities, analogs of wings of birds, the archosaur, according to scientists, used in order that at the movement to cling to branches of trees. This animal could not fly.
Not all stages of evolution of birds by the scientist managed to be traced. There are hypotheses that in the same branch also other classes of animals originate. It is confirmed with the facts – at some of types the structure of a skeleton is similar to the structure of a skeleton of birds, there are similar "nodes" in muscle tissues, undeveloped devices for flight and soaring. A bright example of that – a chameleon and other subspecies of lizards.
Evolution of birds is reflected even in folklore of some nationalities. The transitional stage is represented by dragons, Slavic Zmey Gorynych and other characters. Interesting that, as many scientific hypotheses of evolution of birds and their skeleton confirm fantastic options of succession of events.
Structure of a skeleton of birds
The skeleton of birds differs from skeletons of other living beings in both external, and internal signs. External differences – a shape of a body and skeleton, arrangement of eye-sockets on a skull, lack of an ear entrance (sink), the increased tenacity of fingers on the lower extremities, wings.
The skeleton of a bird consists their several belts:
- skull and cervical belt,
- belt of front extremities,
- pelvic belt.
The skull of modern birds is similar to a skull of their ancient relatives of reptiles. It consists of an occipital part, nadklyuvya, podklyuvya and the hypoglossal device. An occipital part is formed by four bones – the main, two side and top. The skull joint with a backbone provides an occipital condyle which is located under an occipital opening. The roof and sides of a brain box are closed by pair bones – frontal, scaly, parietal and wedge-shaped side. The bottom of a skull is formed by an integumentary wedge-shaped bone.
Difficult part of a skull at birds the beak is considered. It is formed a set of small bones – a crest and nasal bones, pair malar and a square and malar, lower arch, front and ear bones, sochlenovy and tooth parts, the hypoglossal extended body.
The belt of front extremities of a skeleton of a bird is the difficult design formed by a shovel, a clavicle, korakoidy. The feature of this department of a skeleton of birds allowing to fly is that a humeral bone very big and powerful. This factor provides stability of a wing at the loadings characteristic of flight.
The pelvic belt of a skeleton of a bird is formed by accrete sciatic, podvzdoshny and pubic bones. The back extremities underdeveloped in respect of the size, but strong, consist of tubular bones. In structure of paws of birds there is a so-called tsevka which is the additional lever considerably increasing a step. At the majority of bird species the number of fingers on paws is 4, but at some subspecies the ornithologists note a reduction – when under the influence of external factors their quantity changes. Striking examples ostriches – at some types on paws 3 fingers, at some only 2.
One more unique feature of the structure of a skeleton of birds – almost accrete vertebras in its basis. The most mobile department of a backbone of a bird – cervical. The skull is capable to turn instantly on 180 ˚. Inactive chest vertebras connect to sacral department which is not mobile at all and is responsible for ability of a bird to go. Follows it pigostil – the tail department of a backbone which turned during evolutionary changes into a uniform coccygeal bone.
Muscles and skeleton of birds - a whole
Bird – surprising creation of the nature during which evolution there were changes not only in the structure of a skeleton, but also in the structure of muscles and the principles of its connection with a bone basis.
The most developed group of muscles at birds – chest department. Muscle tissues densely fasten to a bone basis of individuals thanks to a so-called keel, a bone outgrowth in a breast. Pectoral muscles at some types make 1/5 part from body lump. They are responsible for ability to lower and raise wings, that is for ability to fly.
On the second place on the level of development and extent of fastening on a skeleton – muscles of back extremities of a bird. Existence of strong, but mobile tendons by means of which individuals are fixed on branches, wires is characteristic of this area of a muscular system and can keep on them a long time. Grasping function – one of the most important functions of a muscular system of the lower extremities of birds. At some types of this class of animals of a muscle of paws (legs) are developed better, than the muscles of front extremities which are responsible for flight. Strength of such types – legs, and they, as a rule, do not fly. The most famous representative of group – an ostrich.
Feathers of birds and their value
Not only the skeleton with the special building and muscles of a bird, but also a pen-type system is responsible for ability to fly. It is formed by down and planimetric feathers. Down are responsible for heat exchange, and planimetric – for movement and protection.
Birds by means of swing planimetric feathers fly. Their most part is located on wings, there are they and on a tail of individuals. Tail planimetric feathers serve as the peculiar wheel directing when soaring.
Structure of swing planimetric feathers of a bird not less difficult, than structure of their skeleton. They are formed by horn small beards of the first and second row. Fastening between them is carried out by hooks which can be considered only under a microscope. Surprisingly as far as such fastenings are strong.
Birds – some of the most surprising creations. At serious evolutionary changes they kept the majority of signs of the ancestors relatives.