What is the developing human organism called from about 2 weeks after fertilization through the second month?

• A. Fetus
• B. Embryo
• C. Blastocyst
• D. Zygote

Answer: (B)

The developing human organism is referred to as an embryo from about two weeks after fertilization through the second month of gestation. During this stage, which lasts from approximately the third week to the eighth week of pregnancy, the foundation for all major organs and structures is laid. This period is critical for development, as the embryo undergoes rapid cell division and differentiation, forming various tissues and systems in preparation for further growth.

The term "zygote" refers to the fertilized egg immediately after the sperm and egg have united but before cell division begins. "Blastocyst" describes the stage that follows the zygote, characterized by the formation of a hollow sphere of cells that implants into the uterus. Finally, the term "fetus" is used starting around the ninth week of gestation, indicating that the organism has moved past the embryonic stage and is now developing more recognizable human features. Understanding these stages is essential for studying human development and prenatal care.