Boys develop new thick hair on the face, experience voice cracking, and may witness occasional enlargement and erection of the penis, often in daydreams or at night.

Girls experience an increase in breast size and darkening of the skin of the nipples. Menstruation also begins during this period.

Sexual reproduction, by combining germ cells from two individuals during fertilization, ensures the reestablishment of the proper number of chromosomes and DNA content in the new generation. This process helps maintain genetic stability and control over cellular functions.

Specialized organs, particularly those involved in reproduction, contain germ cells with half the number of chromosomes and DNA content to maintain a balance and prevent the accumulation of excessive genetic material in each generation.

Meiosis is a cell division process that reduces the chromosome number by half. In specialized organs, germ cells undergo meiosis, resulting in cells with half the chromosomes and DNA content. This ensures that when germ cells from two individuals combine ...