Read the following paragraph and choose the option with the set of words which…
2023
Read the following paragraph and choose the option with the set of words which would fill the blanks correctly in the given order.
During fertilisation, the sperm cell from the father and the egg cell of the mother fuse to form a W which divides repeatedly to give rise to a ball of cells. The cells begin to develop into different organs and tissues. This developing structure called X gets embedded in the wall of Y. The stage of X in which all body parts can be identified is called Z.
W, X, Y, Z respectively are:
- A.
zygote, foetus, uterus, embryo
- B.
zygote, embryo, uterus, foetus
- C.
embryo, zygote, fallopian tube, foetus
- D.
zygote, foetus, fallopian tube, embryo
Show answer & explanation
Correct answer: B
During human reproduction, fertilisation is the fusion of the father's sperm cell with the mother's egg cell into a single fused cell called the zygote. The zygote divides repeatedly by mitosis to form a growing ball of cells; once the cells begin to differentiate into distinct organs and tissues, this developing structure is called an embryo. The embryo becomes embedded in the wall of the uterus, where its development continues. Once every body part of this developing structure has become identifiable, the stage is termed a foetus.
Applying this sequence to the passage: the single cell formed right after fertilisation is W. The ball of cells produced by its repeated division, which develops organs and tissues and embeds in the uterine wall, is X, and the site it embeds in is Y. The later stage of X in which every body part can be identified is Z. Matching the passage against this developmental sequence gives W, X, Y, Z as zygote, embryo, uterus, foetus.
Checking the remaining word-sets against the same developmental facts:
The word-set zygote, foetus, uterus, embryo places the organ-identifiable stage right after the zygote and treats the just-implanted stage as coming after it, reversing which of the two developmental milestones is actually reached first.
The word-set embryo, zygote, fallopian tube, foetus treats the very first cell after fertilisation as already differentiated into organs and tissues, and treats the single fused cell as forming only afterwards; but the single fused cell forms first, before any division or differentiation. It also names the fallopian tube, the site of fertilisation, as the site of implantation.
The word-set zygote, foetus, fallopian tube, embryo places the organ-identifiable stage immediately after the single fused cell, before any implantation step, and again names the fallopian tube, the site of fertilisation, as the implantation site.
Hence, the correct set of terms, in order, is: zygote, embryo, uterus, foetus.