In embryonic development, which stage is formed by the fusion of two gametes?

In embryonic development, which stage is formed by the fusion of two gametes?

• A. Zygote
• B. Morula
• C. Blastula
• D. Gastrula

Answer: (A)

In fertilization, two haploid gametes fuse to form a zygote. This single cell carries a full set of chromosomes, restoring the diploid number, and it becomes the first cell of the new organism. From there, the zygote undergoes rapid cell divisions (cleavage) to form a morula, then a blastula, and eventually a gastrula as development proceeds. The morula is a solid ball of cells, the blastula forms a hollow cavity, and the gastrula introduces the germ layers. So the stage created specifically by the fusion of the two gametes is the zygote.

In fertilization, two haploid gametes fuse to form a zygote. This single cell carries a full set of chromosomes, restoring the diploid number, and it becomes the first cell of the new organism. From there, the zygote undergoes rapid cell divisions (cleavage) to form a morula, then a blastula, and eventually a gastrula as development proceeds. The morula is a solid ball of cells, the blastula forms a hollow cavity, and the gastrula introduces the germ layers. So the stage created specifically by the fusion of the two gametes is the zygote.