CLASS of animal kingdom are found in a variety of habitats – polar ice caps, deserts, mountains, forests, GRASSLANDS and dark caves. Some of them have adapted to fly or live in water. The most unique mammalian characteristic is the presence of milk-producing glands (mammary glands) by which the young ones are nourished.They have two pairs of limbs, adapted for walking, running, climbing, burrowing, swimming or flying.The skin of mammals is unique in possessing hair. EXTERNAL ears or pinnae are present. Different types of teeth are present in the JAW. The heart is four-chambered. They are homoiothermous. Respiration is by lungs. SEXES are separate and fertilisation is internal. Binomial nomenclature of few mammals:Binomial nomenclatureAnimalPanthera leoLionPanthera tigrisTigerBalaenoptera musculusBlue whaleCanis lupusDogFelis catusCatElephas maximus indicusElephantEquus caballusHorse