Characteristics features of mammals: (1) Body is covered with hair. (2) Skin is provided with sweat and sebaceous glands. (3) Heart is four chambered. (4) Fertilization is internal. (5) Females have mammary glands to produce milk to nourish their young ones. (6) External ear-pinna present. (7) Eyes have eye lids. (8) Warm-blooded. (9) Respiration through lungs. (10) Body cavity dividedinto thorax and abdomen by muscular diaphragm.