MCAT Question A Day - 5/26/13 - Answer!
Which of the following sequences is in the correct developmental order?
A. Fertilization, zygote, blastula, morula, gastrula
B. Zygote, fertilization, morula, blastula, gastrula
C. Fertilization, zygote, morula, blastula, gastrula
D. Zygote, fertilization, blastula, morula, gastrula
The correct answer is (C). The zygote forms after the gametes combine during fertilization. The 32-cell morula is followed by the 64-cell blastula, and then the more complex gastrula with its three primary germ layers.
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