Evolution of Birds
It has become widely accepted that birds have evolved from reptiles in the Jurassic period and are the living descendants of a group of dinosaurs called theropods. Birds share hundreds of unique skeletal features with dinosaurs. Over the years, birds have evolved in a wide variety of forms, from flightless and aquatic to flying animals. Due to poor fossil records, some information regarding the evolution of birds are based on theories but during the last 30 years, the evolutionary relationship between birds and dinosaurs have become more firmly established. Some important evolutions of birds were the evolution of feathers, and avian locomotion (Bird evolution, 1996).
The modern bird has been modified significantly. The body evolved in such a way for it to be fit to fly. For example, the front limbs became wings, and their breastbone was enlarged in order to support flight muscles. They also now have light, hollow bones. A significant modification was the evolution of a four-chambered heart, which also changed their circulatory system allowing them to breathe through their lungs (Birds, 1999). The feather was another important modification. Feathers of a bird play a crucial role in a birds flight, and also regulates body temperature. Feathers are believed to be modified reptilian scales, although feathers are a much more complex structure (Aves).
The oldest bird fossil, Archaeopteryx, a member of the theropods is known to be the closest match of a bird. Some characteristics of birds that was present in therapods were wings, feathers, and many skeletal similarities (Birds, 1999). There are two theories on the origin of flight, the "Ground up" and "Trees down" theories. The Ground up theory proposes that the early birds lived on the ground and in order for them to catch prey, they would have to jump. Constant jumping could have caused the jumps to become higher, and their wings would then be used. The "Trees-down" Theory proposes...
Please join StudyMode to read the full document