What distinguishes mammals from other animals?

Explanation

Salient features of Mammals:
1. Their body is covered by hair, a unique feature of mammals. Some of them are adapted to fly or live in water.
2. Presence of mammary glands is the most unique feature of mammals.
3. They have two pairs of limbs adapted for walking, running, climbing, burrowing, swimming and flying.
4. Skin is glandular in nature, consisting of sweat glands, scent glands and sebaceous glands. Exoskeleton includes horny epidermal horns, spines, scales, claws, nails, hooves and bony dermal plates.
5. Teeth are thecodont, heterodont and diphyodont. External ears or pinnae are present. The heart is four chambered and possess a left systematic
6. Mature RBCS are circular, biconcave and non nucleated. Mammals have a large brain when compared to other animals. They show greatest intelligence among all animals.
7. Their kidneys are metanephric and are ureotelic. All are homeothermic, sexes are separate and fertilization is internal. Eg: Oviparous- Ornithorhynchus (Platypus), Viviparous- Macropus (Kangaroo).