Home Subjects NEET Zoology

NEET Zoology

Zoology questions for NEET UG — Animal Kingdom, Human Physiology, Genetics, Evolution.

273 Q 6 Topics Take Test
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Difficulty: All Easy Medium Hard 81–90 of 273
Topics in NEET Zoology
A 26-year-old woman with history of pelvic inflammatory disease presents with infertility. Which imaging modality is MOST appropriate to assess tubal patency?
A Transvaginal ultrasound
B Hysterosalpingography (HSG)
C CT scan of pelvis
D MRI of abdomen
Correct Answer:  B. Hysterosalpingography (HSG)
EXPLANATION

HSG is the gold standard for assessing tubal patency and detecting tubal blockage or damage. It uses radiographic contrast to visualize the fallopian tubes.

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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?
A Hypogonadism
B Obstructive azoospermia
C Varicocele
D Erectile dysfunction
Correct Answer:  B. Obstructive azoospermia
EXPLANATION

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.

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A 28-year-old woman has not conceived after 18 months of unprotected intercourse. Which investigation should be performed FIRST?
A Laparoscopy
B Hysterosalpingography
C Semen analysis of partner
D Endometrial biopsy
Correct Answer:  C. Semen analysis of partner
EXPLANATION

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.

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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?
A Follicle-stimulating hormone (FSH)
B Luteinizing hormone (LH)
C Prolactin
D Thyroid-stimulating hormone (TSH)
Correct Answer:  B. Luteinizing hormone (LH)
EXPLANATION

LH acts on Leydig cells in the testes to stimulate testosterone synthesis and secretion. Low LH indicates secondary hypogonadism.

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During spermatogenesis, which cell type directly gives rise to mature spermatozoa?
A Spermatogonium
B Primary spermatocyte
C Secondary spermatocyte
D Spermatid
Correct Answer:  D. Spermatid
EXPLANATION

Spermatids undergo spermiogenesis (morphological changes) to transform into mature spermatozoa. This is the final stage of spermatogenesis.

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Which of the following pathogens is the leading cause of congenital infections in the TORCH group?
A Toxoplasma gondii
B Rubella virus
C Cytomegalovirus (CMV)
D Herpes simplex virus
Correct Answer:  C. Cytomegalovirus (CMV)
EXPLANATION

CMV is the most common congenital infection, affecting 0.5-1% of live births and causing microcephaly, hearing loss, and developmental delays if acquired in utero.

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Which statement about human milk lactation is correct?
A Lactation begins immediately after delivery
B Oxytocin stimulates milk production (galactopoiesis)
C Prolactin causes milk ejection reflex
D Milk ejection is mediated by oxytocin release
Correct Answer:  D. Milk ejection is mediated by oxytocin release
EXPLANATION

Oxytocin triggers the milk ejection reflex (letdown reflex), while prolactin stimulates milk production. Both hormones are essential for successful lactation.

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A 24-year-old woman with irregular cycles is diagnosed with polycystic ovary syndrome. Which hormonal finding is most characteristic?
A Low LH and high FSH ratio
B High LH to FSH ratio (>3:1)
C High prolactin levels
D Low estrogen and progesterone
Correct Answer:  B. High LH to FSH ratio (>3:1)
EXPLANATION

PCOS is characterized by elevated LH levels relative to FSH (typically LH:FSH ratio >3:1), along with hyperandrogenism and insulin resistance.

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Which of the following is the mechanism of action of levonorgestrel as an emergency contraceptive?
A Uterine wall thinning
B Inhibition of ovulation or alteration of cervical mucus
C Zygote destruction
D Embryo implantation prevention
Correct Answer:  B. Inhibition of ovulation or alteration of cervical mucus
EXPLANATION

Levonorgestrel prevents or delays ovulation when given within 72 hours of unprotected intercourse and may also alter cervical mucus to impede sperm transport.

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A pregnant woman presents with vaginal bleeding in the first trimester and a positive pregnancy test. Pelvic ultrasound shows an empty uterus. What is the most likely diagnosis?
A Threatened abortion
B Incomplete abortion
C Ectopic pregnancy
D Molar pregnancy
Correct Answer:  C. Ectopic pregnancy
EXPLANATION

An empty uterus with positive hCG indicates an ectopic pregnancy (implantation outside the uterus), which may present with vaginal bleeding, abdominal pain, and hemodynamic instability.

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