Question

Which of the following structures are possessed only by birds?

a. Enlarged pectoral muscles and heavy bones
b. 4 chambered heart
c. feathers and keeled sternum
d. a short tail and mammary glands
e. a large brain and endothermy

Answer 1

Feathers and a keeled sternum are unique to birds, adaptations essential to flight. They provide flight control and anchor points for strong flight muscles respectively.

Step-by-step explanation:

Among the structures mentioned, those possessed only by birds are feathers and a keeled sternum. Feathers are crucial for flight, providing insulation and enabling the fine control necessary for aerodynamic efficiency. The keeled sternum, or sternum with a central ridge, provides an anchor point for powerful flight muscles, such as the pectoralis major and the supracoracoideus muscles.

These adaptations are vital for flight, facilitating lift and power. Birds also exhibit traits like a high metabolism, a lightweight but strong skeleton to reduce body weight, and other modifications such as pneumatic bones that contribute to their ability to fly. Moreover, birds have a large four-chambered heart supporting their high metabolism and vigorous flight activity.