Which of the following features helps birds to fly? (a) Hollow bones (b) Modification of forelimbs into wings (c) Strong shoulder bones (d) All of these
Hint: Birds or avians are a class of warm-blooded animals. All birds are placed in the class Aves.
Complete Answer: Birds are mostly characterized by features like: - Feathers - Jawed beaks - Lack of teeth - Gestation of embryo in a hard shelled egg - High rate of metabolism - A four chambered heart - A sturdy lightweight skeleton Birds have a wide variety of sizes. These sizes range from as small as 5 centimeters (Hummingbird) to as big as 3 meters (ostrich). The skeletal system of a bird is made up of very lightweight bones. These lightweight bones of birds have cavities filled with air and these cavities connect to the respiratory system of the bird. These air-filled cavities are called pneumatic cavities. The wings of the bird have developed and evolved from the forelimbs of the ancestors of birds. The ribs of a bird are flattened. Birds have a keeled sternum. This sternum allows the attachment of muscles which are utilized for flying. Birds have strong shoulder bones which help birds.
Therefore, the correct option is answer (d) all of the above.
Note: Birds have around ten thousand species currently alive on Earth. Over half of these species of birds are perching birds. Birds have characteristic wings that may or may not help in flying. The avian digestive system has been developed over the years to accommodate flying. Some birds have adapted to swimming in water as a means of transport.