Class Aves: Aves are a class of endothermic vertebrates, commonly known as birds. These animals fall under the phylum Chordata carrying specific features such as toothless jaws with beak, laying of eggs with a hard shell, etc. 

Characteristics of Class Aves

• Birds are warm-blooded animals.
• Their forelimbs are modified into wings.
• They have well-developed flight muscles that help during the flight.
• Their hind limbs are adapted for walking, hopping, perching, grasping, wading and swimming.
• There are epidermal scales on their legs.
• The endoskeleton is bony with long hollow bones filled with air cavities. known as pneumatic bones.
• Their spindle-shaped body minimizes resistance of the wind.
• The feathers help in preventing heat loss and reduce air friction by providing passage to the air.
• There is no skin gland except the oil gland.
• The lower and upper and jaws are modified into a beak.
• They have no teeth.
• They have sharp eyesight.
• The alimentary canal has a crop and a gizzard. The crops help in softening food, and the gizzard helps in crushing the food.
• Pigeons and other seed-eating birds lack a gall bladder.
• They have spongy and elastic lungs for respiration.
• The special vocal organ called syrinx is present at the base of trachea.
• Their heart is four-chambered.
• RBCs are oval, nucleated and biconvex.
• 12 pairs of cranial nerves are present.
• They have a single ovary and oviduct on the left side
• All the birds are oviparous and exhibit sexual dimorphism. The eggs have four embryonic membranes- amnion, chorion,  allantois, and yolk sac.

Classification of Class Aves

The class Aves is divided into two categories:

Archaeornithes

This class of birds are extinct. They had a toothed beak with a long lizard-like tail.

Eg., Archaeopteryx

Neornithes

These include extant as well as extinct birds. They have no teeth and a short tail.

Eg., Penguin, Grey Heron, Kingfisher, Duck, etc.

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By Team Learning Mantras