Class 12Subject Code: 044Year: 202633 Questions Available

CBSE Class 12 Biology 2026 — QuizCluster Solutions

Comprehensive question-by-question independently authored solutions for CBSE Class 12 Biology Board Examination (2026). Questions are referenced directly to the official CBSE Question Paper.

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Official Source & AttributionSource of question paper: Central Board of Secondary Education (CBSE)

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Q1 of 33

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Sexual Reproduction in Flowering Plants: Double Fertilization & Triple Fusion in Angiosperms

Section A•1 Marks•Chapter: Sexual Reproduction in Flowering Plants

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Question 1 — Problem Statement (Synopsis)

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Explain the events of double fertilization in angiosperms. Differentiate between syngamy and triple fusion with ploidy levels of the resulting structures.

See Question 1 in official CBSE Class Biology Question Paper (2026)

QuizCluster Step-by-Step Solution

Step 1: Pollen tube discharge and Syngamy

The pollen tube enters the ovule through the micropyle and discharges two non-motile male gametes into the cytoplasm of one synergid. Syngamy: One haploid male gamete (n) fuses with the haploid egg cell (n) to form a diploid Zygote (2n), which develops into the embryo.

Step 2: Triple Fusion and Primary Endosperm Nucleus

Triple Fusion: The second haploid male gamete (n) fuses with the diploid secondary central nucleus (2n) formed by two polar nuclei to produce the triploid Primary Endosperm Nucleus (PEN, 3n). Because two types of fusions (syngamy and triple fusion) occur in an embryo sac, the phenomenon is called Double Fertilization.

Final Answer

Syngamy: Male gamete (n) + Egg (n) → Zygote (2n) | Triple Fusion: Male gamete (n) + Polar nuclei (2n) → Endosperm (3n)

Important Core Concept

Double fertilization is unique to angiosperms, ensuring food storage tissue (endosperm) develops only if fertilization is successful.

Common Student Pitfall

Writing endosperm ploidy as 2n instead of 3n in angiosperms.

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Source of question paper: Central Board of Secondary Education (CBSE). QuizCluster provides independently prepared educational solutions and explanations. QuizCluster is an independent educational platform and is not affiliated with or endorsed by CBSE. Question papers are accessed through links to official CBSE resources and are not hosted by QuizCluster.