Which term refers to the developing human organism from about two weeks after fertilization through the second month?

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

Answer: (B)

The stage of development from roughly two weeks after fertilization through the end of the second month is called the embryo. After fertilization, the zygote forms and begins to implant, and starting around two weeks in, the embryonic period focuses on establishing the body’s basic plan and organs. This is when major organ systems begin to form (organogenesis) and the embryo transitions from a simple ball of cells to a recognizable human structure. The fetus stage follows after about eight weeks, when growth continues rather than the major formation of organs. A gamete is a sperm or egg cell, and a zygote is the fertilized single cell—neither term describes this specific developmental window.