Which term is described as the earliest stage of growth after fertilization?

• A. Embryo
• B. Zygote
• C. Egg
• D. Sperm

Answer: (A)

After fertilization, the first cell formed is the zygote. This single cell carries genetic material from both parents and is the initial stage of a new organism. It is the zygote that immediately begins rapid cell divisions to become a multicellular structure, eventually progressing into the embryo as those cells differentiate and organize. The egg and the sperm are the gametes that fuse to start this process, not stages that occur after fertilization. The term embryo describes the developing organism after the initial cells have begun to divide and organize, which comes after the zygote.