What is the term for a fertilized egg?

The term for a fertilized egg is "zygote." This stage occurs immediately after a sperm fertilizes an egg, resulting in a single-cell organism that has the potential to develop into a new individual. The zygote contains a complete set of genetic information, with half of the DNA coming from the mother and half from the father.

Following the zygote stage, the organism undergoes multiple divisions and differentiations. It eventually develops into a blastocyst, which is a stage in early embryonic development characterized by the formation of a hollow ball of cells. The embryo is then formed as cell differentiation continues, leading eventually to the development of a fetus, which is the term used for the developing organism after the eighth week of pregnancy.

Understanding these stages is critical in the field of human development, as each term corresponds to a specific point in the developmental timeline and indicates the organism's growth and differentiation stage.