Final answer:
Menarche and spermarche are significant events in physical development, representing the beginning of reproductive capacity in girls and boys respectively.
Step-by-step explanation:
Menarche and spermarche are terms related to the physical development of individuals. Menarche is the onset of the first menstrual period in girls, indicating the beginning of reproductive capability. Spermarche, on the other hand, refers to the first occurrence of ejaculation in boys, signifying the ability to father a child. Both menarche and spermarche are important milestones in the process of puberty and reproductive maturation.
Learn more about Physical development and puberty