The evolution of birds. Part one

The evolution of birds. Part one

The evolution of birds. Part one

and the bird loses its ability to fly.


Her wingless auk (now exterminated) penguins have lost it. Flying limits the absolute size of the bird. A bird the size of an African ostrich could not fly because of its size. Flying ancestors of ostrich were significantly smaller. The fact is that as the linear dimensions of a bird increase in a certain number of times, its volume and, consequently, its mass increases in proportion to the cube of this size, and the surface of the wings and others expressed by area are only proportional to the square. Thus, per unit area of ​​wings in larger birds accounts for more units of mass than in small ones. Some reduction in wing loading in large birds is achieved by the fact that the area of ​​their wings relative to body length is very large, i.e. the principle of geometric similarity is disturbed as the size of birds increases in evolution: large birds with huge wings. This is easy to verify by comparing the silhouettes of, for example, a soaring eagle and a flying crow. Mountain birds (condor, vultures, eagles) have the largest size, using the usual ascending air currents in the mountains. However, their flapping flight is difficult to control, and when they were carried away from the mountains by a strong wind, they almost lost their ability to plan a flight. Limited evolution to flight has led to a great similarity of all birds belonging to different orders. Waterfowl, fleeing bustard and mostly flying swift, differ incomparably less than each other than, for example, a dolphin, a hare and a bat among mammals. Birds - warm-blooded vertebrates with constant body temperature, adapted to flight. They originated from reptiles and have a similarity with them in the structure of the body, but the adaptations to flight were very strongly reflected in their morphology, that is, they became special characteristic features. The signs of the bird class are as follows. The forelegs are turned into wings. The outer covers are feathers. Body shape is streamlined. There are no teeth, but there is a beak. The skeleton is strong, the bones are fused. The lungs are spongy and hollow. The heart is four-chamber, there is one right aortic arch. All birds are egg-laying. Birds are spread across the globe - from the coasts of the Arctic Ocean to Antarctica. At present, there are up to 8500 species of birds belonging to 40 orders on the globe. credit card dumps

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