In Ulothrix/Spirogyra/Chlamydomonas, reduction division (meiosis) occurs at the time of

Options

A. Gamete formation
B. Zoospore formation
C. Zygospore germination
D. Vegetative reproduction.

Answer

**Step-by-Step Solution:**

1. **Understanding the Organisms**: The question mentions three organisms: Ulothrix, Spirogyra, and Chlamydomonas. These are all green algae that exhibit a haploid gametophytic phase in their life cycle.

2. **Identifying the Life Cycle Stages**: In the life cycle of these organisms, there are two main phases: the haploid phase (gametophyte) and the diploid phase (sporophyte). The haploid phase produces gametes, while the diploid phase produces spores.

3. **Meiosis in the Life Cycle**: Meiosis, or reduction division, is the process that reduces the chromosome number by half, resulting in haploid cells. In these algae, meiosis occurs during the formation of gametes or spores.

4. **Zygospore Formation**: When two haploid gametes fuse, they form a diploid zygote, which develops into a zygospore. The zygospore is a resting spore that can survive adverse conditions.

5. **Germination of Zygospore**: When favorable conditions return, the zygospore undergoes meiosis to produce haploid zoospores. This is the key point where reduction division occurs.

6. **Conclusion**: Therefore, in Ulothrix, Spirogyra, and Chlamydomonas, reduction division (meiosis) occurs at the time of zygospore germination.

**Final Answer**: Reduction division (meiosis) occurs at the time of zygospore germination.

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