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NEET Zoology

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

540 Q 6 Topics Take Test
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Difficulty: All Easy Medium Hard 161–170 of 540
Topics in NEET Zoology
Q.161 Medium Reproductive Health
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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Which of the following intrauterine devices (IUDs) releases hormones to prevent pregnancy?
A Copper-T IUD
B Levonorgestrel-releasing IUD (LNG-IUD)
C Lippes loop
D Non-medicated IUD
Correct Answer:  B. Levonorgestrel-releasing IUD (LNG-IUD)
EXPLANATION

The LNG-IUD releases levonorgestrel directly into the uterine cavity, causing endometrial atrophy and thickened cervical mucus, with effectiveness lasting 3-7 years.

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A couple has been trying to conceive for 2 years without success. The male partner has normal semen parameters, but the female partner has elevated FSH levels. What does this indicate?
A Polycystic ovary syndrome
B Diminished ovarian reserve
C Hyperprolactinemia
D Thyroid dysfunction
Correct Answer:  B. Diminished ovarian reserve
EXPLANATION

Elevated basal FSH (>10 IU/L on day 3) indicates reduced ovarian reserve, meaning fewer eggs remain in the ovaries, affecting fertility prognosis.

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Q.164 Medium Reproductive Health
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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Q.165 Medium Reproductive Health
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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A 35-year-old woman with three previous cesarean deliveries presents with vaginal bleeding at 32 weeks. What is the most likely diagnosis?
A Placental abruption
B Placenta previa
C Placenta accreta
D Morbidly adherent placenta
Correct Answer:  C. Placenta accreta
EXPLANATION

Multiple cesarean deliveries increase the risk of abnormal placentation, including placenta accreta, where placental villi invade the myometrium, leading to hemorrhage.

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Q.167 Medium Reproductive Health
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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Q.168 Medium Reproductive Health
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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Q.169 Medium Reproductive Health
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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Q.170 Medium Reproductive Health
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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