Origin of Birds

Origin of Birds

  The origin of birds has been a controversial topic as the modern birds did not fit easily with the rest of the modern animals on Earth. They have four chambered heart and are warm blooded (endothermic) like mammals but had scales on their feet and legs and laid eggs like reptiles. Archaeopteryx is the oldest known bird and a transitional fossil first discovered just a few years after Charles Darwin published On the Origin of Species. This is Charles Darwin’s scientific theory that a population of organisms evolve into new species over generations because of natural selection. Archaeopteryx had feathers and other characteristics of modern birds but also had the common features with theropod dinosaurs like small teeth, claws on their forelimbs, and a long boney tail as well. 

  It now believed modern birds evolved from theropod dinosaurs during the Mesozoic Era. The fossils of theropod dinosaurs and of early Mesozoic era birds have many common physical features. They show the same behaviors raising their young and nest building. Later it was discovered using molecular studies of Tyrannosaurus Rex and Hadrosaur fossils that birds are closely related to the dinosaurs than to crocodiles. 

 

  Modern birds have feathers, wings, and light weight strong hollow bones. They have a beak but no teeth. Most birds can fly and are active during the day. They lay hard eggs usually in a nest. There are at least 10,000 living species of birds that live on all seven continents and on almost every island in every ocean. Birds live in many different kinds habitats including the Polar Regions. Some bird like the penguins spends most of their lives swimming under water after fish. Most of them are social animals living in groups. Parrots and crows are the most intelligent birds and they live in close communities using complex social interactions with each other.    

  

  They have an exceptionally efficient breathing system. Using air sacs coupled to air spaces in some hollow bones the fresh air is force to the lungs as the bird exhales. The bird’s lungs are always inflated with fresh oxygen rich air at all times even as they breathe out. A large fast beating heart to pumps the oxygen around the circulatory system to feed the powerful muscles used for flight.