Why can birds fly but penguins can ?
Of all animals, birds are perhaps best known for their ability to fly, but many kinds of birds are flightless. Penguins belong to a group called Sphenisciformes, in which all species are flightless and aquatic. Another group of flightless birds is known as the ratites. It includes the ostriches of Africa, rheas of South America, emus of Australia, cassowaries of New Guinea and Australia, moas (now extinct) and kiwis in Australia, and elephant birds of Madagascar (an extinct group that includes the largest birds ever known). Other flightless birds include a species of cormorant in the Galapagos, a grebe in the Andes, a parrot in New Zealand, and several species of pigeons on islands in the South Pacific and Indian Oceans.The anatomy and brain structure of flightless birds indicate that they all descended from ancestors that could fly. In many cases, flightless birds inhabit islands where there are no predators.
