When the zygote of Ulothrix and Chlamydomonas divide, which of the following does not happen?

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  1. Of the four, three nuclei degenerate.
  2. Four haploid daughter nuclei are formed.
  3. Each haploid nucleus gives rise to a zoospore.
  4. Each zoospore upon germination gives rise to a new plant.

Answer (Detailed Solution Below)

Option 1 : Of the four, three nuclei degenerate.
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Detailed Solution

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The correct answer is Of the four, three nuclei degenerate

Concept:

  • Zygote Formation: In organisms like Ulothrix and Chlamydomonas, the zygote is formed through the fusion of gametes.
  • Meiosis in Zygote: The zygote undergoes meiosis, resulting in the formation of four haploid daughter nuclei.
  • Zoospore Formation: Each of these haploid nuclei can develop into a zoospore, which upon germination gives rise to a new plant.

Explanation:

  • Of the four, three nuclei degenerate: This statement is incorrect because in Ulothrix and Chlamydomonas, all four haploid nuclei formed after meiosis typically develop into zoospores. None of the nuclei degenerate.
  •  Four haploid daughter nuclei are formed: This is correct. After the zygote undergoes meiosis, it results in four haploid daughter nuclei.
  • Each haploid nucleus gives rise to a zoospore: This is correct. Each of the four haploid nuclei develops into a zoospore.
  • Each zoospore upon germination gives rise to a new plant: This is correct. Each zoospore, upon germination, develops into a new individual, completing the life cycle.

Conclusion:

In summary, during the division of the zygote in Ulothrix and Chlamydomonas, all four haploid daughter nuclei form zoospores, and none of them degenerate. Therefore, the correct answer is that three nuclei do not degenerate, which is why Option 1 is incorrect.

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