Early Embryonic Cleavage Division — NEET Biology

Correct answer: A — B → E → C → A → F → D

This question requires arranging key events in human reproduction and embryonic development in their correct chronological order. 1. **(B) Formation of zygote:** This is the first event, resulting from the fusion of male and female gametes during fertilisation (Section 2.5). 2. **(E) Cleavage divisions leading to morula:** The zygote undergoes mitotic divisions (cleavage) as it moves through the oviduct, forming 2, 4, 8, 16 daughter cells called blastomeres, eventually forming a morula (Section 2.5). 3. **(C) Blastocyst formation and its attachment to the uterine wall:** The morula continues to divide and transforms into a blastocyst, which then attaches to the endometrium (implantation) (Section 2.5). 4. **(A) Differentiation of inner cell mass into germ layers:** Immediately after implantation, the inner cell mass differentiates into ectoderm, endoderm, and mesoderm (germ layers) (Section 2.6). 5. **(F) Formation of chorionic villi from trophoblast:** After implantation, finger-like projections appear on the trophoblast called chorionic villi (Section 2.6). 6. **(D) Appearance of limbs and digits:** This is a later developmental milestone; by the end of the second month of pregnancy, the foetus develops limbs and digits (Section 2.6). Therefore, the correct chronological sequence is B → E → C → A → F → D.