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Biology · 2025 · 2 marks
CBSE 2025 · Region 7 · Set 1 · Q18
(a) "A fully developed foetus initiates its delivery from the mother's womb." Explain.
(a)
"A fully developed foetus initiates its delivery from the mother's womb." Explain.
OR
(b)
Give reasons for the following :
(i)
Why can a woman generally not conceive a child after $\displaystyle 50$ years of age ?
(ii)
Polar bodies are formed during oogenesis and not during spermatogenesis.
Marking-scheme solution
Signals for parturition arise from fully developed foetus and placenta which induce mild uterine contractions, called foetal ejection reflex, this triggers release of oxytocin from maternal pituitary, which act on uterine muscle and causes stronger uterine contractions.
(i)
Menstrual cycle ceases / menopause occur around $\displaystyle 50$ years of age.
(ii)
During oogenesis Meiosis I and II are unequal divisions which form one large cell and a smaller polar body / The unequal cell formation will ensure that the large cell has more cytoplasm and more nutrient reserve for better survival of the zygote.
Meiosis I and II are equal divisions in spermatogenesis.
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CBSE Class 12 Biology past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.