Biology Q102 – NEET-UG 2023

Home Biology Plant ReproductionQuestion #354

In angiosperm, the haploid, diploid and triploid structures of a fertilized embryo sac sequentially are :

Clue 1 of 3: Understanding Ploidy in Angiosperms

Recall the ploidy levels (haploid, diploid, triploid) of different cells and structures within an angiosperm embryo sac, especially after fertilization.

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Ninja Strategy•Sequential Ploidy Check

Systematically check the ploidy level (haploid, diploid, triploid) for each structure listed in the options against the required sequence.

🧠 Full Solution Path

Step 1: Recall Ploidy Levels in a Fertilized Embryo Sac✦ Active

In a fertilized angiosperm embryo sac, various structures have distinct ploidy levels: * Haploid ( $n$ ) structures: Synergids, Antipodals (though they degenerate after fertilization, they are initially haploid). * Diploid ( $2 n$ ) structures: Zygote (formed by the fusion of egg cell ( $n$ ) and male gamete ( $n$ )). * Triploid ( $3 n$ ) structures: Primary Endosperm Nucleus (PEN) (formed by the fusion of two polar nuclei ( $n + n$ ) and one male gamete ( $n$ )).

💡 Teacher's Secret Hint

The question specifically asks for structures in a *fertilized* embryo sac, so consider the products of double fertilization.

Step 2: Evaluate Options for Haploid (n) Structure○ Expand

We need to find an option that starts with a haploid structure, as per the sequence (haploid, diploid, triploid): * (1) Synergids ( $n$ ) - Possible * (2) Antipodals ( $n$ ) - Possible * (3) Synergids ( $n$ ) - Possible * (4) Synergids ( $n$ ) - Possible

💡 Teacher's Secret Hint

Both synergids and antipodals are haploid and present in the embryo sac, though they are ephemeral after fertilization.

Step 3: Evaluate Options for Diploid (2n) and Triploid (3n) Structures Sequentially○ Expand

Now, let's check the subsequent diploid and triploid structures in the correct order: * (1) Synergids ( $n$ ), Primary endosperm nucleus ( $3 n$ ), Zygote ( $2 n$ ) - Incorrect order ( $3 n$ before $2 n$ ). * (2) Antipodals ( $n$ ), synergids ( $n$ ), Primary endosperm nucleus ( $3 n$ ) - Incorrect (second structure is also $n$ , not $2 n$ ). * (3) Synergids ( $n$ ), Zygote ( $2 n$ ), Primary endosperm nucleus ( $3 n$ ) - Correct sequence. * (4) Synergids ( $n$ ), antipodals ( $n$ ), Polar nuclei ( $n + n$ before fusion, but in a fertilized sac, they form $3 n$ PEN) - Incorrect (second structure is also $n$ , not $2 n$ ). Therefore, option (3) correctly lists the haploid, diploid, and triploid structures sequentially.

💡 Teacher's Secret Hint

Double fertilization is key: one male gamete forms the $2 n$ zygote, and the other forms the $3 n$ primary endosperm nucleus.

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Biology Question 102 – NEET-UG 2023

Clue 1 of 3: Understanding Ploidy in Angiosperms

🧠 Full Solution Path