1. The body is covered with feathers and the forelegs are modified into two wings.
2. Their necks are elongated and S-shaped.
3. The jaws are toothless and have evolved into beaks.
4. Intraskeletal pores, bone hard, light and airy. Bones contain air-filled cavities.
5. Air sacs exist in the lungs. The sphincter consists of the syrinx, the organ that produces sound.
6. They are endothermic or warm-blooded animals. That is, their body temperature does not change with the rise and fall of the environment temperature.
7. The heart has four chambers, 2 atria and 2 ventricles.
8. Their digestive system consists of crop and gizzard. So able to digest energy food quickly. Dr. Siddiq Publications
9. The crown of the head is connected to the spinal cord by an occipital condyle. The sternum forms a boat-like keel.
10. They are bipedal and can fly.
11. Their feet have clawed toes.
12. They lay eggs. The egg hatches and the baby comes out.
13. Newborn babies are active and vigorous or naked and weak.
[key words to remember characteristics: feather, wing, neck, beak, air cavity, air sac, syrinx, endothermic, heart, digestive system, occipital condyle, keel, biped, toe, egg] Dr. Siddiqu Publications