Q49.Arrange the events in correct order of sequence :
A. Cleavage
B. Fertilization
C. Morula
D. Gastrula
E. Blastula
Choose the correct answer from the options given below :
(1) A, B, E, C, D
(2) B, A, C, E, D
(3) B, C, A, E, D
(4) B, C, E, D, A
The correct sequence of embryonic development events is B, A, C, E, D—Fertilization, Cleavage, Morula, Blastula, Gastrula—making option (2) right.
Option Analysis
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Option (1) A, B, E, C, D: Wrong—cleavage (A) can’t precede fertilization (B); morula (C) follows blastula (E) incorrectly.
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Option (2) B, A, C, E, D: Correct—starts with fertilization forming zygote, then cleavage divisions produce morula (solid 16-cell ball), blastula (fluid-filled with blastocoel), and gastrula (three germ layers form).
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Option (3) B, C, A, E, D: Wrong—morula (C) before cleavage (A) impossible; cleavage creates morula.
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Option (4) B, C, E, D, A: Wrong—cleavage (A) last defies logic; it’s the first post-fertilization division.
Struggling to arrange cleavage fertilization morula gastrula blastula in order? This NEET Q49 guide breaks down the exact embryonic development timeline—perfect for scoring in Human Reproduction. Option (2) B-A-C-E-D nails it every time.
Embryonic Development Timeline
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Fertilization (B): Sperm meets egg in fallopian tube, forming diploid zygote.
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Cleavage (A): Zygote undergoes rapid mitotic divisions (no growth)—produces 2, 4, 8, 16 blastomeres.
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Morula (C): ~16-cell solid berry-like stage (day 3); travels to uterus.
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Blastula (E): Morula becomes fluid-filled blastocyst (~100 cells, day 4-5) with inner cell mass (future embryo) and trophoblast.
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Gastrula (D): Cells migrate, forming three germ layers—ectoderm, mesoderm, endoderm (week 2-3).
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Mnemonic: Fertilization → Cleavage → Morula → Blastula → Gastrula (FC-MB-G).
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Traps: Don’t confuse morula (solid) vs blastula (hollow); cleavage precedes both.
