Question

Which of the following are characteristics of class Aves?
1. They are cold-blooded animals.
2. They are warm-blooded animals.
3. Their heart is four-chambered.
4. Their heart is three-chambered.
A) 1 and 3
B) 2 and 3
C) 1 and 4
D) 3 and 4

Answer 1

Aves are classified into two categories namely Archaeornithes that have toothed beak, long tail and are extinct. Example; Archeopteryx. Other is, Neornithes that are extinct as well as living in the present day and have no teeth and have a short tail. Example peacock, parrot, eagle, sparrow, etc.

Complete answer: Characteristic features of Aves:
i. They are warm-blooded as they can maintain their internal body temperature
ii. Teeth are absent
iii. Forelimbs are modified into wings for flying and hindlimbs helps in swimming, walking grasping and other movements
iv. Long hollow bones are present and are known as pneumatic bones. Air cavities are present inside the bones.
v. Legs are covered by epidermal scales.
vi. Only skin gland present is an oil gland.
vii. Feathers provide insulation by preventing heat loss.
viii. The beak is modified upper and lower jaw.
ix. Lungs are present for respiration.
x. Vocal organ is known as syrinx and they have a four-chambered heart.
xi. The alimentary canal consists of a crop which softens the food and gizzard which crushes the food.
xii. The gall bladder is absent and RBCs are nucleated, biconvex and oval.
xiii. Only one ovary is present and oviduct on the left side. They are oviparous because they lay eggs and are sexually dimorphic.
Hence, the correct answer is option B.

Note: All species belonging to class Aves have a four-chambered heart consisting of two atria and two ventricles. There is a complete separation of oxygenated and deoxygenated blood. Also, Aves are warm-blooded i.e they maintain a constant body temperature inside their body. Warm-blooded animals are also called homeothermic animals.