Photo Credits. Primary and secondary sexual characteristics are physical traits that make males and females look and behave differently from each other in certain species, including humans. Young adolescents will notice hair growing in new places on their bodies, such as their underarms and groins.
See also: Mate choice. For more information about the biological and hormonal changes that trigger these changes, and for suggestions about guiding young teens through this process, please refer to the article on Puberty in the Middle Childhood series. Male birds and fish of many species have brighter coloration or other external ornaments.
Williams Textbook of Endocrinology E-Book. Buy options. Testosterone Therapy and Prostate Cancer. As adolescents continue to mature they become better able to move their bodies with greater skill and precision.