During which stage of early embryonic development do the primary germ layers form?

• A. Gastrulation
• B. Fertilization
• C. Blastulation
• D. Cleavage

Answer: (A)

Verified step by step guidance

1. Understand the stages of early embryonic development: Fertilization, Cleavage, Blastulation, and Gastrulation.
2. Fertilization is the process where the sperm cell fuses with the egg cell to form a zygote.
3. Cleavage is the series of rapid mitotic cell divisions that the zygote undergoes, leading to the formation of a multicellular structure.
4. Blastulation follows cleavage and results in the formation of the blastula, a hollow ball of cells.
5. Gastrulation is the stage where the blastula reorganizes into a three-layered structure known as the gastrula, forming the primary germ layers: ectoderm, mesoderm, and endoderm.