Is the bird an animal or not? Class of Birds

Often you can hear the question: are the birds animals or not? Having studied all the features of the structure and activities of representatives of this class, it will be possible to answer it with confidence.

General characteristics

The Bird class includes 9000 species, united in the following order: unkempt, or running (ostriches, kiwis), penguins, or floating (penguin imperial, spectacled, Magellan, Galapagos, crested, etc.), keeled, or flying (chicken, pigeon, passerine , Goose and others).

Birds are similar in structure to reptiles and represent a progressive branch that has been able to adapt to flight. Their forelimbs have evolved into wings during evolution. Birds are characterized by a constant body temperature, characteristic of higher vertebrates, therefore, birds are warm-blooded animals. This is the first answer to the question "Is the bird an animal or not?".

Birds owe their origin to the oldest reptilian pseudohooks with a similar structure of hind limbs.

Body and skin

The body of the birds has a streamlined shape with a small head and a long, movable neck. The trunk ends with a tail.

Skin thin, dry, practically devoid of glands. Only some birds (waterfowl) have the coccygeal gland, which produces a fat-like secret with water-repellent properties. Horny formations (derivatives of the epidermis of the skin) cover the beak, claws, scales of fingers and forge (lower part of the shin). Feathers are also derived from the skin. They are divided into two groups: contour and downy. Contouring, in turn, are steering (flight control), flywheel (maintaining the bird in the air), as well as covering (located on top of the body). Under the contour are down feathers. They contribute to the preservation of body heat. During moult, older feathers completely fall out, and new ones grow in their place.

Skeleton and muscular system

In birds, the skeleton is particularly strong and lightweight due to cavities in bones filled with air. It consists of the following sections: cervical and thoracic, lumbar and sacral, and also caudal. Extremely mobile is the cervical section due to a number of vertebrae. In the thoracic region, the vertebrae tightly fuse and carry ribs, movably connected to the breastbone and forming a thorax. To attach the muscles that cause the wings to move, on the sternum there is a protrusion - keel. As a result of the intergrowth of the lumbar and sacral, as well as partially caudal vertebrae between themselves and the pelvic bones, a sacrum is formed, serving as a support for the hind limbs.

The muscular system in birds is well developed. Depending on the ability to fly, special development is achieved by certain departments. In birds that fly well, the muscles that drive the wing are well developed, and those who have lost this ability are the muscles of the hind limbs and neck.

Digestive and excretory systems

The digestive system is characterized by a lack of teeth. To grasp and hold food, a beak with horny covers on the jaws is used. Through the mouth, food gets into the pharynx, and after it - into the long esophagus, which has a pocket-like extension (goiter) to soften it. The posterior end of the esophagus opens into the stomach, which is divided into two sections, glandular and muscular (here the food passes mechanical rubbing). The intestine consists of the duodenum, which opens the ducts of the liver, and the pancreas, as well as the small and short rectum, ending with a cloaca. This structure promotes the rapid removal of undigested residues out.

To the organs of the allocation of birds are paired kidneys and ureters, which open into the cloaca. From it, urine, along with feces, is taken out.

Respiratory system

Respiratory organs in birds are maximally adapted to flight. Through the nasal cavity, air enters the pharynx and the trachea, which is divided into two chests in the chest. Here is the voice device. Getting into the lungs, the bronchi strongly branch. The lungs themselves have a complex structure and consist of numerous through tubes. Some of them expand, forming air sacs, they are located between internal organs, muscles and in tubular bones. Birds are characterized by double breath. This is due to the fact that during flight the air passes through the lungs twice: when it is sucked on the wing stroke and ejected when lowered due to the compression of the bags.

Nervous system

The organization of the nervous system in birds is quite complex and similar to that of higher vertebrates. This again gives an affirmative answer to the question "Is the bird an animal or not?" There is a system of two divisions: the brain and spinal cord. In the head section, the cerebellum, which is responsible for the coordination of movements, as well as the front hemisphere and the midbrain, are responsible for complex forms of behavior. The spinal cord is most developed in the shoulder, lumbar and sacral areas, which provides good motor functions. These features also give a clear affirmative answer to the question "Is the bird an animal or not?"

The behavior of birds is based on unconditioned (innate) reflexes: nutrition, reproduction, nesting, laying eggs, mating games, singing. Unlike the class of reptiles, they can form and consolidate conditioned (acquired in the course of life) reflexes, which indicates their highest stage of evolution. One of the examples of conditioned reflexes can be the fact of their successful domestication by a man. It is believed that birds are pets that easily rearrange their behavior and lifestyle from wild (natural) type to cultural (domestic).

Circulatory system

The organs of the circulatory system of birds, as in most higher vertebrates, are represented by a four-chambered heart, consisting of atria (2) and ventricles (2), as well as vessels. Their blood is completely divided into venous and arterial blood. It passes two circles of blood circulation (small, large).

Reproduction

Birds are dioecious animals with a complex and highly developed system of mating behavior, breeding offspring with eggs and caring for them.

All of the above characteristics of the class give an unambiguous answer to the question "Is the bird an animal or not?" Of course, birds are related to animals.