Zoology in NEET is memory heavy but not memory only, because the diagram based and assertion reason questions need understanding. This set runs through human physiology, animal kingdom and classification, structural organisation, genetics and evolution, biotechnology, and ecology. Explanations point to the NCERT line the question came from, so revision stays anchored to the source text.
During spermatogenesis, which cell type directly gives rise to mature spermatozoa?
Answer: D
Spermatids undergo spermiogenesis (morphological changes) to transform into mature spermatozoa. This is the final stage of spermatogenesis.
Q.42Medium
A 40-year-old man presents with erectile dysfunction and is found to have low testosterone levels. Which of the following hormones directly stimulates testosterone production in Leydig cells?
Answer: B
LH acts on Leydig cells in the testes to stimulate testosterone synthesis and secretion. Low LH indicates secondary hypogonadism.
Q.43Medium
A 28-year-old woman has not conceived after 18 months of unprotected intercourse. Which investigation should be performed FIRST?
Answer: C
Male factor infertility accounts for 40% of cases. Semen analysis is non-invasive, cost-effective, and should be the first investigation when evaluating an infertile couple.
Q.44Medium
A 32-year-old man presents with azoospermia. Semen analysis shows normal seminal fluid parameters but absence of spermatozoa. What is the most likely diagnosis?
Answer: B
Normal seminal fluid with absent sperm indicates obstruction in the reproductive tract rather than failed production. This is obstructive azoospermia, often due to vasectomy, absence of vas deferens, or ejaculatory duct obstruction.
Q.45Medium
A 26-year-old woman with history of pelvic inflammatory disease presents with infertility. Which imaging modality is MOST appropriate to assess tubal patency?
Answer: B
HSG is the gold standard for assessing tubal patency and detecting tubal blockage or damage. It uses radiographic contrast to visualize the fallopian tubes.
Q.46Medium
A woman using combined oral contraceptive pills (COCs) presents with breakthrough bleeding. Which action should be taken?
Answer: B
Breakthrough bleeding is common in the first 3 months of COC use and usually resolves spontaneously. Continuation of the same regimen is recommended unless bleeding persists beyond 3 months.
Q.47Medium
Which contraceptive method is absolutely contraindicated in women with current or history of breast cancer?
Answer: B
Combined oral contraceptives containing estrogen are contraindicated in breast cancer patients due to estrogen's proliferative effects. Copper IUD, progestin-only methods, and barrier methods are safe alternatives.
Q.48Medium
A 34-year-old man has oligozoospermia with motility of 20%. Which of the following is the most likely etiology?
Answer: D
Varicocele is the most common correctable cause of male infertility. Fever temporarily affects spermatogenesis for 2-3 months. Smoking reduces sperm count and motility. All are valid etiologies of oligozoospermia.
Q.49Medium
What is the window period during which emergency contraception is most effective?
Answer: C
Levonorgestrel (Plan B) is effective within 120 hours (5 days) if taken within 72 hours for maximum efficacy. Ulipristal acetate (a selective progesterone receptor modulator) can be used up to 120 hours.
Q.50Medium
Which of the following best describes the mechanism of action of levonorgestrel IUD in preventing pregnancy?
Answer: B
Levonorgestrel IUD works primarily by altering the endometrium to prevent implantation and secondarily by thickening cervical mucus. Complete ovulation inhibition occurs in only 20-30% of cycles.
Q.51Medium
A 31-year-old woman presents with secondary amenorrhea and infertility. Blood tests show elevated prolactin levels. What is the next appropriate investigation?
Answer: B
Elevated prolactin requires MRI of pituitary to rule out prolactinoma, which is the most common pathological cause of hyperprolactinemia. Thyroid tests should be done to exclude hypothyroidism as a cause.
Q.52Medium
A 35-year-old woman with polycystic ovary syndrome (PCOS) seeks contraception with metabolic benefits. Which method would be most appropriate?
Answer: A
Combined OCPs with anti-androgenic progestins (like cyproterone acetate or spironolactone) provide contraception while treating PCOS-related hyperandrogenism and improving metabolic parameters.
