CBSE 2026 · Region 4 · Set 3 · Q23 · 3 marks
(a)Draw a diagram of human ovum prior to fertilization. Label any four parts.(b)Explain how polyspermy is avoided during fertilization.
(a)
Draw a diagram of human ovum prior to fertilization. Label any four parts.
(b)
Explain how polyspermy is avoided during fertilization.
Marking-scheme solution
(a)
(b)
When a sperm comes in contact with the zona pellucida layer of the ovum it induces changes in the membrane that blocks the entry of additional sperm thus avoiding polyspermy.
Human ReproductionFertilisation and ImplantationApplyshort_answermedium
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CBSE Class 12 Biology past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.