Final answer:
Sexual reproduction involves the fusion of sperm and egg, resulting in a fertilized zygote. This process can occur either inside or outside the female's body, known as internal or external fertilization, and leads to genetic diversity among offspring.
Step-by-step explanation:
Sexual reproduction occurs when two sex cells from different individuals, known as gametes, unite to form a new organism, through a process called fertilization. This critical juncture of combining genetic material can take place either inside (internal fertilization) or outside (external fertilization) the female's body. During internal fertilization, sperm are transferred into the female's body, where they travel to meet the egg, as seen in human reproduction. In contrast, external fertilization involves the release of gametes into the environment, such as how frogs reproduce. The fertilized egg, or zygote, is a diploid cell, meaning it has twice the number of chromosomes compared to the haploid gametes.
The process of sperm production in males is called spermatogenesis, which results in haploid sperm. After the fusion of sperm and egg, the zygote embarks on a developmental journey that ends with the birth or hatching of a new individual. Thus, sexual reproduction provides a mechanism for genetic diversity among offspring, contributing to the evolutionary adaptability of a species.