NEET Zoology PYQs

In Agave, the vegetative propagule is called a bulbil. A bulbil is a small bulb-like shoot that forms on the plant and can develop into a new plant when separated. This concept is described in NCERT under vegetative propagation, where bulbil formation is noted for certain plants like Agave. The other options are different structures: a rhizome is an underground stem; an offset is a small plant produced at the base of the parent (common in some aquatic or succulent plants); an eye is a bud or a part of a stem that can give rise to a new shoot. Thus bulbil is the correct term for Agave’s vegetative propagule.

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.

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).

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.