Human Reproduction: Modes & Gamete Ploidy — NEET Biology

Correct answer: B — S3, S4 and S5

The core concept here relates to the stages of early embryonic development and their characteristics. S1 is correct: Fertilisation takes place in the ampullary region of the fallopian tube. (NCERT, Page 35, 'The ovum released by the ovary is also transported to the ampullary region where fertilisation takes place.') S2 is correct: The morula is an embryo with 8 to 16 blastomeres formed after cleavage. (NCERT, Page 36, 'The embryo with 8 to 16 blastomeres is called a morula.') S3 is NOT correct: The inner cell mass, not the trophoblast layer, differentiates as the embryo. The trophoblast layer gets attached to the endometrium. (NCERT, Page 37, 'The trophoblast layer then gets attached to the endometrium and the inner cell mass gets differentiated as the embryo.') S4 is NOT correct: The zygote is diploid, formed by the fusion of two haploid gametes. (NCERT, Page 36, 'Soon the haploid nucleus of the sperms and that of the ovum fuse together to form a diploid zygote.') S5 is NOT correct: Implantation involves the embedding of the blastocyst into the endometrium, not the myometrium, of the uterus. (NCERT, Page 37, 'the blastocyst becomes embedded in the endometrium of the uterus... This is called implantation.') Therefore, statements S3, S4, and S5 are not correct.