A zygote is the initial cell formed when two gamete cells, such as a sperm and an egg, fuse during fertilization. This marks the beginning of a new organism. The zygote contains all the genetic information necessary for the development of a new individual.
During sexual reproduction, a sperm cell from the male parent fertilizes an egg cell from the female parent. This union forms the zygote. The zygote then undergoes a series of divisions and differentiations to develop into a mature organism.