Though the human species differ in colour, size and looks but they belong to same species of homosapiens who were the descendends of homo eurectus or an upright man and are classified as mammals in animalia . further they have same body and metabolic organisation .they are multicellular heterotophs. they have 206 bones, 32 teeths, two eyes with (pupil and retina),one nose etc. their forelimbs are modified to catch, hold things, and their hindlims are modified for locomotion they differ because of the environmental and climatic conditions where they live. and due to evolution they contain different genetic information(DNA) or heridity and differ in size, behaviour, colour and looks. for eg. a man living in south america appears more white in colour to the man living in africa((NOT BEING A RACIST)).