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Biology · 2025 · 5 marks
Sexual Reproduction in Flowering PlantsPre-fertilisation: Structures and Events5 marksUnderstandlong answer
CBSE 2025 · Region 7 · Set 3 · Q32
(a) What is meant by 'right' and 'wrong' type of pollen when pollen lands on the stigma. A two-celled right type pollen has landed on the stigma.…
(a)
What is meant by 'right' and 'wrong' type of pollen when pollen lands on the stigma. A two-celled right type pollen has landed on the stigma. Explain the events taking place till fertilization in angiosperms. Why is pollen pistil interaction said to be dynamic ?
OR
(b)(i)
Give the schematic representation of oogenesis in h female indicating chromosome number at each step.
(ii)
In which part of the female reproductive system do the following events take place ? I. Formation of corpus luteum II. Maturation of tertiary follicle III. Fertilisation IV. Implantation
Marking-scheme solution
• Right – Compatible
Wrong – Incompatible
• Two-celled pollen grain on the stigma germinates to form pollen tube
through germ pore, generative cell divides and forms the two male gametes during the growth of pollen tube in the stigma, pollen tube enters ovule through micropyle then enters one of the synergids through the filiform apparatus, pollen tube releases two male gametes, one male gamete(n) fuses with egg cell(n) to form zygote (2n) thus completing syngamy, other male gamete fuses with polar nuclei in central cell to form primary endosperm nucleus (3n) termed triple fusion.
• Involves pollen recognition , Promotion or inhibition of (formation of
pollen tube) the pollen.
(i)
Oogenesis in Female Human
(Representation with correct labelling and ploidy)
(ii)
(I)
Formation of corpus luteum – Ovary
(II)
Maturation of tertiary follicle – Ovary
(III)
Fertilisation – Ampullary region of oviduct
(IV)
Implantation – Endometrium of uterus
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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.