About Lesson
Characteristics of Class Aves
- Their bodies are covered with feathers for insulation and flight.
- Have beaks.
- Have hollow bones.
- The sternum is enlarged to form a keel for attachment of flight muscles.
- The fore limbs are modified into wings for flight.
The hind limbs are for walking or swimming.
Some birds cannot fly e.g. ostrich.
- The hind limbs have scaly skin.
- Have double circulation with a four-chambered heart, which has 2 atria and 2 ventricles.
The systemic arch of the circulatory system is on the right.
- Have lungs for gaseous exchange. Have air sacs, which store air. The air in the air sacs helps in lowering the body density for flight.
- They are endothermic (homoeothermic).
- Fertilisation is internal. They lay yolky eggs with calcareous shells.
- Have an internal auditory meatus.
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