You all must already know that in general, humans with XX combination of chromosomes are called females while those having XY combination of chromosomes are called males. The terms female and male represent types of sex in human beings. Sex is biologically determined. This means that biological characteristics (in this case, genetic material / chromosomes) help decide the sex of a person. During adolescence, with the onset of puberty, the sex of a person becomes further prominent through the development of secondary sexual characters. You must have learnt about this in the chapter – “Reaching the age of adolescence”. Can you give some examples of how human females and males can be biologically different?