Human Reproduction — NEET UG practice

1. Check statement A.

Spermatogonia are diploid cells present in the testis. They first multiply by mitotic division to increase their numbers before some of them undergo further changes to become primary spermatocytes. So spermatogonia do not always undergo meiotic division — Statement A is incorrect.

2. Check statement B.

Once formed, a spermatogonium increases in size and becomes a primary spermatocyte. This primary spermatocyte then undergoes the first meiotic division (meiosis I), not mitosis, to produce two secondary spermatocytes. So Statement B, which says this division is mitotic, is incorrect.

3. Check statement C.

Each secondary spermatocyte undergoes the second meiotic division (meiosis II), producing haploid spermatids. This matches the biology correctly, so Statement C is correct.

4. Check statement D.

Spermatids do not become spermatozoa through mitosis — instead, they undergo a special transformation process. So Statement D is incorrect.

5. Check statement E.

The process by which spermatids transform into mature, motile spermatozoa is called spermiogenesis. This is correctly stated, so Statement E is correct.

6. Conclusion.

Only statements C and E are correct.

Hence, the answer is B.

1. Recall the timeline of key foetal milestones during human pregnancy.

Human pregnancy is tracked in weeks, and specific developmental milestones occur at specific stages.

2. Match milestone A: foetus movement and hair on head.

The first movements of the foetus, along with the appearance of hair on the head, are usually observed during the fifth month, which corresponds to 20 weeks of pregnancy. So, A matches with II.

3. Match milestone B: limbs and digits.

By the end of the second month (8 weeks) of pregnancy, the foetus develops limbs and digits. So, B matches with III.

4. Match milestone C: external genital organs.

By the end of the first trimester (12 weeks), most major organ systems are formed, and the limbs and external genital organs become well developed. So, C matches with IV.

5. Match milestone D: fine hair, eyelids, and eyelashes.

By the end of the second trimester (24 weeks), the foetal body is covered with fine hair, the eyelids separate, and eyelashes are formed. So, D matches with I.

6. Conclusion.

The correct matching is A-II, B-III, C-IV, D-I.

Hence, the answer is B.

1. Recall the structures that surround the female gamete (ovum).

The ovum released at ovulation is not a single bare cell — it is surrounded by several protective layers, arranged concentrically from the outside going inward.

2. Identify the outermost layer.

The outermost layer is the corona radiata, made up of follicular cells that remain attached to the oocyte even after it leaves the ovary.

3. Identify the next layer moving inward.

Just beneath the corona radiata lies the zona pellucida, a thick transparent glycoprotein layer that directly surrounds the oocyte.

4. Identify the space between the zona pellucida and the ovum.

Between the zona pellucida and the ovum's own cell membrane lies a narrow fluid-filled gap called the perivitelline space.

5. Identify the innermost boundary.

The innermost structure is the plasma membrane of the ovum itself, which directly encloses the cell's cytoplasm.

6. Put it all together, from outer to inner.

The correct order is: Corona radiata → Zona pellucida → Perivitelline space → Plasma membrane of ovum, i.e., C, A, B, D.

Hence, the answer is C.