Human Reproduction PYQs

AI-generated explanation. Check against your textbook.

Relaxin is secreted by the corpus luteum during the later phase of pregnancy. It helps in the remodeling of connective tissue and relaxation of the pelvic ligaments to aid childbirth, and also supports the uterus during pregnancy as progesterone does. Thus option 2 is correct.

Relaxin reaches peak levels in the later stages of pregnancy and works with other hormones to prepare the birth canal for delivery.

Corpus luteum of ovary secretes progesterone and relaxin during pregnancy, aiding uterus in sustaining pregnancy and preparing for parturition.

AI-generated explanation. Check against your textbook.

Ovulation is triggered by a surge in luteinising hormone (LH) from the anterior pituitary, which is caused by a high level of estrogen released by the graphsian (mature) follicle as the follicular phase peaks. Thus, a high concentration of estrogen induces the LH surge leading to ovulation. The other options are incorrect: progesterone rises after ovulation, not before; low LH or low FSH does not trigger ovulation.

In the menstrual cycle, estrogen rises during the follicular phase and peaks just before ovulation, causing the LH surge that releases the egg.

Estrogen-induced LH surge leads to ovulation.

AI-generated explanation. Check against your textbook.

The secondary oocyte is arrested in metaphase II and completes meiosis II only after fertilization. When a sperm fuses with the ovum, the oocyte finishes meiosis II, forming the mature ovum and a second polar body. Hence, the meiotic division is completed at the time of fusion of a sperm with an ovum (option 4).

Fertilization triggers the last meiotic division, ensuring the haploid number is restored in the zygote.

The secondary oocyte completes meiosis II only upon fertilization, forming the mature ovum.

AI-generated explanation. Check against your textbook.

In meiosis, cells become haploid (n) after the first division or as gametes. Secondary spermatocyte is haploid (produced after meiosis I in spermatogenesis). The first polar body is also a haploid product of meiosis I. The ovum (egg) is a haploid gamete after meiosis. Thus all three in option 2 are haploid. Other options mix diploid and haploid cells (e.g., primary oocyte and spermatogonia are diploid; spermatid is haploid but not with the others in that group). Therefore option 2 is correct according to NCERT concepts of haploid cells in human gametogenesis.

During oogenesis, the first polar body divides or may not; in humans, the secondary oocyte completes meiosis II only after fertilization, producing the ovum and a second polar body.

Haploid cells contain a single set of chromosomes (n). In human gametogenesis, meiosis I and II produce haploid products such as secondary spermatocytes, polar bodies, and ova.

AI-generated explanation. Check against your textbook.

The correct sequence is: Seminiferous tubules → Rete testis → Vasa efferentia (efferent ductules) → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Urethral meatus. This aligns with NCERT, where sperm pass from seminiferous tubules to rete testis, then through the efferent ductules into the epididymis, onward via the vas deferens, then the ejaculatory duct and finally the urethra and its external opening.

Rete testis acts as a network connecting seminiferous tubules to the efferent ducts, facilitating sperm collection before their transport.

Semen path: seminiferous tubules → rete testis → efferent ductules → epididymis → vas deferens → ejaculatory duct → urethra.

AI-generated explanation. Check against your textbook.

In flowering plants, two male gametes are released from the pollen tube. One sperm nucleus fertilizes the egg cell to form the zygote, while the other sperm nucleus fertilizes the central cell (which contains the two polar nuclei) to form the endosperm nucleus. The central cell fertilization typically involves the fusion of one sperm with the polar nuclei, resulting in the triploid endosperm. After fertilization, the synergid degenerates. Thus, one male gamete fuses with the egg and the other fuses with the central cell nuclei, matching option 1.

Double fertilization is unique to angiosperms and leads to diploid zygote and triploid endosperm formation.

Two male gametes: one fuses with egg to form zygote; other fuses with central cell to form endosperm.

AI-generated explanation. Check against your textbook.

The second polar body is formed when the egg completes its second meiotic division. In human/animal oocytes, this division is completed after the sperm enters the ovum, but before the actual union of genetic material (fertilization) is complete. Thus, extrusion of the second polar body occurs after entry of the sperm but before fertilization, making option 4 correct as per the given answer.

The first polar body is formed after the first meiotic division and is often smaller; the second polar body forms at the end of meiosis II in the egg.

Meiosis II in the egg completes after sperm entry; the second polar body is extruded during this process before fertilization completes.