What name is given to those sexual characteristics in humans:
(A) which are present in babies at birth?
(B)which develop in mature boys and girls.

Dear Student,

A) No such significant changes can be seen/observed between male and female children up to 12 years or so other than having respective genital organs, the presence of long hair in females. 

B) Changes occur during their maturation in boys or girls is called as puberty. Puberty is a process of sexual and physical change that occurs in the human body during maturity. The total duration of puberty can be considered as puberty age. It varies in boys and girls. Girls begin puberty at ages 10-11 and usually complete it by 15-17. Boys begin puberty at ages 11-12 and usually complete it by 16-17.
 
Changes at puberty:

(i) Sudden increase in height and weight.

(ii) Broadening of shoulders and widening of chest in boys. In girls, the region below waist becomes wider.

(iii) In boys, under the influence of hormones, the larynx becomes prominent, the vocal cords become longer and thicker. These changes cause the voice to become hoarse.

(iv) Appearance of hair in areas such as underarms, face, hands, and legs.

(v) Appearance of acne as a result of excessive secretion of oil from skin.

(iv) Testis grows and starts producing sperms in males, whereas in females, the ovary enlarges and starts producing matured eggs.




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