Question

Which of the following is found only in birds?

• A. Gizzard for grinding food as teeth are absent.
• B. Wings
• C. Direct development
• D. Beak

Answer 1

The correct option is D

Beak

Class Aves show following exclusive characteristics.

• Presence of feathers
• Their forelimbs are modified into wings.
• The hind-limbs are adapted for perching, walking or swimming, etc.
• The upper and lower jaws are modified into a beak, which lacks teeth.
• Endoskeleton is fully ossified (bony) and the long bones are hollow with air cavities (pneumatic) to reduce weight.
• Most of the bones are firmly fused together, which help in flight.
• Female has usually well developed single left ovary and oviduct.

Presence of gizzard, direct development and presence of wings are the characters shown by invertebrate animals as well.