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Birds 1

Page history last edited by Stephan Arthur Joanides 13 years, 1 month ago

Approximately ten thousand bird species share the world with humans. Approximately ninety bird species have gone extinct since 1681.

The vast majority of these vertebrates move by flying. Birds have a backbone so they are called vertebrates.

A birds skeleton is completely bony and aerodynamically suitable for flying. Long bones are tubular and therefore extremely light. The skull is fixed to the backbone only with one vertebra just like in the Reptilia Class. A beak is created by prolonging the upper and the lower jaw. A neck is quite long and very movable. A chest bone is wide with a number of muscles, especially those responsible for flying, are fixed to it. Even the bone in the wings is attached to the chest bone. The birds’ body is covered with feathers. It is extremely light and on the other hand it is also a thermal isolation. Feather lies in two layers.

-birds are endothermic amniotes.

-They have a specialized wing shape that produces lift for flight.

-Feathers, which function in both flight and endothermy.

- Numerous weight-reducing features

- A birds heart beats 400 times per minute when resting and beats 1000 times per minute while flying.

Birds have a unique cover – feathers. These consist of a special substance called keratin which gives birds extraordinary skills. Birds are extremely old animals. First birds lived 140 million years ago! These days there are approximately 8 600 different birds’ types which live and fly all around the world

The oldest bird was known as an Archaeopteryx and lived about 150 million years ago. It was the size of a raven, was covered with feathers, and had wings.

The birds breathe with lungs however these cannot be extended. The lung capacity is extended by five pairs of air sacks which store the air. These sacks are located next to some inner organs and tubular bones. Some birds have got even a vocal organ. The heart is divided into two atriums and two ventricles. Deoxygenated blood flows through the right heart where as the oxygenated blood flows through the left heart. So there are two separated blood circulations.

The average body temperature is about 42 Celsius degrees. In the brain we can observe a huge development especially in the frontal part. Birds use their instinct very much, besides they take care of their offspring.

All birds lay eggs. There are three main layers in the egg. Amnion is filled with amniotic fluid (reptiles have got amnion as well), then chorion and alantois. Alantois is used as a respiratory and a secretory organ. The female birds have got only one ovary. There are often differences in sexes. This is called sexual dimorphism.

All birds lay eggs!

The Bird Class can be divided into two infraclasses: Saururae and Ornithurae.
Infraclass Saururae includes already extinct birds. They had been a link between reptiles and birds. They were able to climb trees but unable to fly. Their jaws were pretty sharp.

The second Infraclass includes few extinct birds and also a number of birds which can be seen all around the world.