Bird
Birds have wings. The wings develop differently in different species. The only known groups of birds without wings are the extinct moa and the elephant birds. Wings evolved from the forelimbs of birds. They give birds the ability to fly. Over time, many groups of birds evolved with smaller wings. These include ratites, penguins and many island species of birds. The digestive and respiratory systems of birds are also adapted for flight. Some bird species in aquatic environments have evolved as good swimmers. This is seen in seabirds and some waterbirds.