Which is not a stage during human reproduction? a) blastula b) embryo c) spore d) zygote

Spores are produced by plants, bacteria, and fungi, but the zygote, the embryo, and the blastula are all stages in the development of the human body.
Human reproduction starts with the joining of two haploid sex cells, the egg, and the sperm cells. When those two fuse in the process of fertilization, they form the zygote which is the one cell that is the basis of the human development.
After the fertilization, the zygote starts to divide, making two cells, those two cells divide again making four cells and so on. Those cells start to stick to each other and form layers, which is called the blastula stage.
With further divisions of the cells and layer development the cells of the blastula, called blastocysts eventually form the embryo.
The embryo has three distinct layers, the ectoderm (which later develops into skin and the nervous system ), the mesoderm ( which later develops into muscles and blood cells) and the endoderm (which later develops into internal organs).

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