Birds are feathered friends of man. Their role in nature is invaluable. Read about their origin, significance and protection in the article.
Birds: General Description
Birds are highly organized warm-blooded animals. In nature, there are nine thousand species of modern birds. The characteristic features of the class are the following features:
- Feathers.
- Rigid cornea beak.
- No teeth.
- A pair of forelimbs turned into wings.
- The chest, pelvic girdle and the second pair of limbs have a special structure.
- The heart consists of four chambers.
- There is an air bag.
- The bird incubates eggs.
Birds, the general characteristics of which are presented above, due to these features are able to fly. This distinguishes them from other classes of animal vertebrates.
Appearance on earth
The origin of birds is explained by several theories. According to one of them, birds are supposed to live on trees. At first they jumped from branch to branch. Then they glided, then made small flights within one tree and finally learned to fly in open space.
Another theory suggests that the origin of the birds is related to the ancestors of birds, which were four-legged reptiles. Evolving, the scales became feathers, which allowed the reptiles to jump, flying a short distance. Later animals learned to fly.
The origin of birds from reptiles
Based on this theory, we can say that the ancestors of the birds were also creeping reptiles. At first, their nests were on the ground. This attracted predators who constantly destroyed nests with their chicks. Caring for their offspring, reptiles settled in the thick of tree branches. At the same time, a hard shell began to form on the eggs. Before that, they were covered with a film. Instead of scales, feathers appeared that served as a source of heat for the eggs. The limbs became longer and covered with plumage.
The origin of birds from ancient reptiles is obvious, according to scientists. The ancestors of the birds begin to take care of their offspring: they feed the chicks in the nest. To do this, solid food was crushed into small pieces and put it in the beaks of babies. With the ability to fly, primitive birds of the ancient period of time could better defend themselves from the attacks of their enemies.
Ancestors - Waterfowl
The origin of birds, according to another theory, is associated with their waterfowl. This version owes its existence to the remains of ancient birds that were found in China. According to scientists, they were waterfowl and lived more than a hundred million years ago.
According to the theory, birds and dinosaurs lived together for sixty million years. Among the finds were feathers, muscles, membranes. Exploring the remains, paleontologists made the following conclusion: the ancestors of ancient birds swam. To get food from the water, they dived.
What are birds and reptiles like?
If you study the origin of birds, it is not difficult to find similarities between them and representatives of other classes. Plumage is the most noticeable feature of the appearance of birds. Other animals do not have feathers. This is the difference between birds and other animals. Signs of similarity are as follows:
- The toes and tarsus of many birds are covered with scales from the cornea and shields, as in reptiles. So, scales on the legs can replace feathers. Characteristically, the beginnings of feathers in birds and reptiles do not differ. Only birds then develop feathers, and reptiles develop scales.
- Investigating the origin of birds, the features in which are similar to incredible reptiles, scientists have determined that the jaw apparatus is more noticeable. Only in birds did it turn into a beak, while in reptiles it remained the same as in turtles.
- Another sign of the similarity of birds and reptiles is the skeletal structure. The skull and spine are articulated with only one tubercle located in the occipital region. Whereas in mammals and amphibians, two tubercles are involved in this process.
- The location of the pelvic girdle of birds and dinosaurs is the same. This is evident from the skeleton of the fossil. This arrangement is associated with a load on the pelvic bones when walking, since only the hind limbs are involved in holding the body.
- Birds and reptiles have a four-chamber heart. In some reptiles, the septum of the chambers is incomplete, and then the arterial and venous blood mix. Such reptiles are called cold-blooded. Birds have a higher organization, compared with reptiles, they are warm-blooded. This is achieved by eliminating the vessel that carries blood from the vein into the aorta. In birds, it does not mix with arterial.
- Another similar feature is hatched eggs. This is typical for pythons. They lay about fifteen eggs. Snakes curl up over them, forming a kind of canopy.
- Most of all the birds are similar to reptiles, which in the first stage of their development are similar to fish-like creatures with tails and gills. This makes the future chick similar to other vertebrates in the early stages of development.
Differences of birds from reptiles
When paleontologists study the origin of birds, they compare the facts and finds, collected bit by bit, and find out how the birds are similar to reptiles.
What are their differences, read below:
- When the birds first wing appeared, they began to fly.
- The feathered body temperature does not depend on external conditions, it is always constant and high, while reptiles fall asleep during the cold weather.
- In birds, many bones are spliced, they differ in the presence of a spider.
- The birds have air sacs.
- Birds build nests, hatch eggs and feed the chicks.
Poultry
Currently, fossils of ancient birds have been found. After careful research, scientists came to the conclusion that they all belong to the same species, which lived one hundred and fifty million years ago. These are archeopteryx, which means "ancient feathers" in translation. Their difference from today's birds is so obvious that the archeopteryx was separated into a separate subclass - lizard-tailed birds.
Ancient birds are little studied. The general characteristic is reduced to determining the appearance and some features of the internal skeleton. The poultry was small in size, about the size of a modern magpie. Her forelimbs had wings, the ends of which ended with three long fingers with claws. The weight of the bones is large, so the ancient bird did not fly, but only crawled.
Habitat - coastal areas of marine lagoons with dense vegetation. The jaws had teeth and the tail had vertebrae. No connections have been made between Archeopteryx and modern birds. The poultry were not the direct ancestors of our birds.
Importance and conservation of birds
The origin of birds is of great importance in biogeocenoses. Birds are an integral part of the biological chain and participate in the circulation of living matter. Feeding herbivorous birds are fruits, seeds, green vegetation.
Different birds play a different role. Grain-eating - eat seeds and fruits, individual species - store them, transporting them over long distances. On the way to the storage place, the seeds are lost. So there is the resettlement of plants. Some birds have the ability to pollinate them.
The role of insectivorous birds in nature is great. They control the number of insect populations by eating them. If there were no birds, the destructive activity of insects would be irreparable.
Man, as far as possible, protects birds and helps them survive in harsh winters. People everywhere hang up temporary nests. Tits, flytraps, and blue tit settled in them. Winter periods are characterized by a lack of natural food for birds. Therefore, birds should be fed, filling the nesting place with small fruits, seeds, bread crumbs. Some birds belong to commercial species: geese, ducks, hazel grouse, capercaillie, black grouse. Their value to humans is great. Woodcock, waders, snipe are of sporting interest.
