question_answer 20)

  Birds and mammals share one of the following characteristics as a common feature. (a) Pigmented skin          (b) Pneumatic bones      (c) Viviparity             (d) Warm blooded body

Answer:

                  (d) Warm blooded animals can maintain constant body temperature, irrespective of the surrounding environment, i.e., their body temperature is fixed. Warm blooded body is the common characteristic feature in birds and mammals. This characteristic was first evolved in higher reptiles, birds and mammals acquire this feature from higher reptiles during evolution. Pigmented skin is the adaptive feature in mammals, and is not present in birds. Pneumatic bones are found only in birds as their flight adaptation. These reduce bodyweight for flight. Viviparity is shown by mammals and not by birds as they are oviparous, i.e. lay eggs.