Why do Aves have bones with air cavities?

Why do males have Penis?

Why do we have seasons on Earth?

Why do we sweat ?

Why do birds have hollow bones?

Complete the following paragraph by selecting the correct option Pelvic girdle consists of two coxal bones. Each coxal bone is formed by the fusion of three bones (i) ,(ii) and (ii) . At the point of fusion of the above bones is a cavity called (iv) to which the thigh bone articultes. The two halves of the pelvic girdle meet ventrally to form the pubic symphysis containing (v) cartilage.

Why do astronauts have to wear protective suits when they are on the surface of moon?

Why do mosses thrive only in moist habital ?