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Biology · 2024 · 5 marks
CBSE 2024 · Region 5 · Set 2 · Q32
(a) (i) Describe the events of spermatogenesis with the help of a A schematic diagram. (ii) Explain the role of hormones in spermatogenesis.
(a)(i)
Describe the events of spermatogenesis with the help of a A schematic diagram.
(ii)
Explain the role of hormones in spermatogenesis.
OR
(b)(i)
Show the development of megaspore mother cell upto the formation of mature embryo sac in flowering plants with the help of labelled diagrams only.
(ii)
How does geitonogamy differ from xenogamy ?
(iii)
Name the type of flowers that are invariably autogamous.
Marking-scheme solution
(a)
Spermatogonia → Primary spermatocytes (mitosis) → Secondary spermatocytes (1st meiotic division) → Spermatids (2nd meiotic division) → Spermatozoa (differentiation); chromosome number per cell $\displaystyle 46$ → $\displaystyle 23$ → 23.
(ii)
LH stimulates Leydig cells in testis to produce androgens, which helps in spermatogenesis.
FSH stimulates the Sertoli cells to produce factors, that help in spermiogenesis.
(b)
(ii)
Geitonogamy is the transfer of pollen grains from the anther to the stigma of another flower of the same plant - xenogamy is the transfer of pollen from anther to the stigma of another plant.
(iii)
Cleistogamous flowers or the flowers which never open
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CBSE Class 12 Biology past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.