State the characteristics of the most evolved class in the animal kingdom.

(N/A) The most evolved class in the animal kingdom is Class Mammalia. Its characteristics are as follows:
$1$. Habitat: They are found in a variety of habitats like polar ice caps,deserts,mountains,forests,grasslands,and dark caves.
$2$. Adaptations: Some have adapted to fly (e.g.,Bat) or live in water (e.g.,Blue Whale).
$3$. Mammary Glands: The presence of milk-producing glands (mammary glands) is a unique characteristic,by which the young ones are nourished.
$4$. Limbs: They have two pairs of limbs,adapted for walking,running,climbing,burrowing,swimming,or flying.
$5$. Skin: The skin of mammals is unique in possessing hair.
$6$. External Ears: Pinnae (external ears) are present.
$7$. Dentition: Different types of teeth (incisors,canines,premolars,and molars) are present in the jaw.
$8$. Heart: The heart is four-chambered. The aortic arch curves to the left.
$9$. Physiology: They are homoiothermous (warm-blooded) animals. Sexes are separate and fertilization is internal.
$10$. Reproduction: They are generally viviparous (giving birth to young ones) with direct development,with few exceptions like the oviparous Platypus (Ornithorhynchus).
$11$. Examples: Platypus (Ornithorhynchus),Kangaroo (Macropus),Bat (Pteropus),Blue Whale (Balaenoptera).