What term describes the process when sperm joins an egg, resulting in the formation of a new organism?

The process by which sperm joins an egg, leading to the formation of a new organism, is called fertilization. During fertilization, a sperm cell penetrates the egg, resulting in the fusion of their genetic materials. This union creates a zygote, which then begins the developmental process that can lead to the formation of an embryo and eventually a fully developed organism.

Fertilization is a crucial step in sexual reproduction, as it combines the genetic information from both parents, ensuring genetic diversity in the offspring. In contrast, ovulation refers to the release of an egg from the ovary, gestation is the period during which the fertilized egg develops into a fetus, and reproduction is a broader term that encompasses all processes involved in creating new organisms. Thus, fertilization specifically describes the moment of sperm-egg union, making it the correct choice.