Question

The flight muscles of birds are attached to
(a) Coracoid
(b) Scapula
(c) Clavicle
(d) Keel

Answer 1

Hint: The flight muscles of the birds are attached to an extension of the sternum also known as a carina. These special muscles of birds that help them to fly are called flight muscles.

Complete answer:
In birds, the extension of the sternum is called a Keel. The muscular system in birds is highly modified to adapt to the aerial mode of life. It acts as an anchor to which the flight muscles of the birds are attached.
- Birds are feathered bipeds truly flying vertebrates except for ostrich and kiwi etc.
- Four limbs are modified into limbs. They possess a beak and streamlined body.
- Sternum with keel is also known as a carina.
- The collar bone which is present between the sternum and the shoulder blade is called the clavicle.
- The shoulder bone that connects the humerus to the collar bone Is known as the scapula.
- A hook-like structure present on the scapula or the shoulder bone is known as coracoid.
- In modern birds, wings are well developed and adapted for flight (except for few) . Tails are short and reduced
- Endoskeleton is fully bony and long bones are hollow with air cavities. Such bones are called pneumatic bones and they lack bone marrow.
- The three types of flight muscles are pectoral muscles, accessory muscles, and tensor muscles.
So, the correct answer is ‘Keel’.

Note: In flightless birds, flight muscle attachments are vestigial as the flight function is lost. So, the Keel sternum is absent in flightless birds for flight muscle attachment. An exception to this however is the penguins that have evolved and adapted to flying through the water and hence retain the keel sternum.